The Value of Electrodiagnostic Consultation for Patients With Upper Extremity Nerve Complaints - A...

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The Value of Electrodiagnostic Consultation for Patients With Upper Extremity Nerve Complaints: A Prospective Comparison With the History and Physical Examination Andrew J. Ha@, MD, Huey-Ming Tzeng, PhD, RN, Diane Belongia LeBreck, MS, MA

ABSTRACT. Haig AJ, Tzeng H-M, LeBreck DB. The value of electrodiagnostic consultation for patients with upper extremity nerve complaints: a prospective comparison with the history and physical examination. Arch Phys Med Rehabil 1999;SO: 1273-81.

Objectives: To determine whether electrodiagnostic testing changes diagnostic certainty compared with a detailed history and physical examination, and whether interactions between medical information, the extent of testing, and diagnostic certainty imply a need for advanced medical knowledge on the part of the tester.

Design: Prospective observation. Setting: University orthopedic department and small commu-

nity hospital electrodiagnostic laboratories. Patients: Two hundred fifty-five consecutive referrals for

upper extremity nerve complaints. Outcome Measures: Diagnosis, diagnostic confidence, and

severity of neurologic lesion were coded after standardized history and physical and after electrodiagnostic testing.

Results: Electrodiagnostic testing substantially altered 42% of diagnoses, confirmed 37%, and did not clarify 21%. The extent of testing correlated with the size of the differential diagnosis, the number of previous hospitalizations, and the number of other medical problems. Confidence in final diagnoses correlated positively with severity of the lesion, but negatively with the size of the differential diagnosis and the number of painful body areas. Hospitalizations and medical problems also tended towards negative correlations.

Conclusions: This study, in which all electrodiagnostics, histories, and physical examinations were performed by a single physician, suggests that electrodiagnosis substantially alters clinical impressions in a large percentage of patients. The complex relationship between clinical information, the extent of testing, and final diagnostic certainty suggests that special- ized medical knowledge is required for accurate electrodiagnosis.

o 1999 by the American Congress of Rehabilitation Medi- cine and the American Academy of Physical Medicine and Rehabilitation

From The Spine Program, Department of Physical Medicine and Rehabilitation, The University of Michigan (Dr. Haig), and Statprob, Inc. (Dr. Tzeng), Ann Arbor; and the Center for Rehabilitation Services, Theda Clark Regional Medical Center, Neenah (Ms. LeBreck), WI. Ms. LeBreck is currently a consultant in Lena, WI.

Submitted for publication September 1, 1998. Accepted in revised form May 10, 1999.

Presented (Best Poster Award) at the 1998 meeting of the Association of Academic Physiatrists. February 18-22, 1998, Atlanta, GA.

No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated.

Reprint requests to Andrew J. Haig. MD, Department of Physical Medicine and Rehabilitation, University of Michigan Health System, 1500 East Medical Center Drive, Ann Arbor. MI 4X109-0042.

0 1999 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation

0003-9993/99/8010-5195$3.00/O

H EALTH CARE REFORM has resulted in efforts to prove the usefulness of various medical interventions with

increasing levels of sophistication. l-4 Although electrodiagnostic consultation has long been deemed valuable, claims that such consultation is effective are under scrutiny.5 Arguments for and against the use of electromyography (EMG), or consultation with an electrodiagnostic medicine specialist, are complex. Appropriate measures range from basic neurophysiology to societal impact.

A simple test, for instance an orthodromic transpalmar median sensory nerve conduction study, is validated through several measures. First, there is the refinement of the test itself, including demonstration of the ability to measure physiologic, biomechanic, or other characteristics, often in an animal or laboratory-based model.6 The next step is demonstration that the same parameters can be measured in healthy humans. This involves establishment of norms, perhaps for different ages or populations7 Following this, the test must be shown to differentiate healthy persons from those with a certain disease or pathology.* The test must then be compared to other tests for the same disease in terms of sensitivity, specificity, risks, cost, and availability.* Quality control for a single nerve conduction study (NCS) may include measurement of reproducibilitygJO or monitoring of technical aspects of tests such as skin tempera- ture or distance measurements’l

More recently, the impact of a constellation of tests on longer-term outcome has been emphasized; for example, a standardized protocol including needle EMG, motor NCS, and sensory NCS in carpal tunnel syndrome may be assessed for its impact on diagnosis, morbidity, mortality, quality of life,8 and patient satisfaction.12.13 Quality assurance here revolves upon standardized protocols across institutions.14,15 Finally, the impact of the test on all of these outcomes for the specific disease is compared at a payer and societal level to the impact of the same resources spent elsewhere, either in medical intervention for other disorders or on more global issues such as reducing national debt.

Electrodiagnosis, however, is not just a simple test. Based on referral information, which may be faulty,12.16,17 and clinical diagnosis that may include non-nerve disorders,‘* the electromyographer uses his/her judgment to choose from hundreds of individual nerve conduction tests’ and dozens of muscles available for needle examination.1g The electromyographer must have skill in interpreting the individual results and integrating those interpretations into the patient’s clinical picture. This is made complex by the fact that individual anatomy and clinical involvement in a disease process may be highly variable. Finally, the tester must have enough knowledge of the medical impact of his/her conclusions to effectively and appropriately communicate the interpretation to patients and referral sources who may have varying levels of sophistication.20,21

The value of specialist consultation in electrodiagnostic testing is contested.5 Is there a need for a consultation with a specialist physician trained in electrodiagnostic medicine, as

Arch Phys Med Rehabil Vol 80, October 1999

1274 VALUE OF ELECTRODIAGNOSTIC CONSULTATION, Haig

stated by the American Association of Electrodiagnostic Medi- cine (AAEM) position statement,22 or can the technical portion of the test be performed by a technician under the auspices of a physician who is not trained in the field (such as an orthopedic surgeon) or by an independent physical therapist, as is the case in many states?

The few studies of referrals to electrodiagnostic laboratories suggest that medical skills are needed to arrive at the appropriate diagnosis in a clinically important number of cases. Roija and colleagues17 demonstrated in 798 patients referred for electrodiagnostic evaluation of cervical radiculopathy that, depending on the specialty of the referring physician, 14% to 35% actually had carpal tunnel syndrome with no radiculopathy, and 9% to 32% had cervical radiculopathy and at least one additional neurologic diagnosis. Dillingham and colleagues18 have shown that of 75 patients referred with a question of cervical radiculopathy, non-neurologic diagnoses (including myofascial pain, shoulder impingement, deQuervain’s tenosy- novitis, or lateral epicondylitis) commonly explained some component of the complaint. In that study, 68% of persons with negative EMG had non-neurologic diagnoses. These studies suggest that in contrast to the referral diagnosis, alternative neurologic diagnoses, multiple neurologic diagnoses, and non- neurologic diagnoses may actually explain the symptoms of persons sent for electrodiagnostic testing.

A possible criticism of this reasoning is that a skilled referral source would not have missed these alternate, multiple, or non-neurologic diagnoses. In Roija’s study, for instance, it is possible that the primary care physicians sent cases for cervical radiculopathy evaluation that would have been diagnosed as carpal tunnel syndrome by a more expert specialist. It is possible that the expert surgeons referred only cases where they were aware of complex diagnostic possibilities. In essence, a competent referring physician would not have need for advanced clinical judgment on the part of the person performing the electrodiagnostic testing.

Research to assess the effect of clinical information and test results on decision-making is behavioral in nature. Fiedler and Parkz3 described their experience in a new capitated contract for electrodiagnostic services. For a year and a half, 455 patients were referred for electrodiagnostic consultations from a population of 25,000. Forty-six percent had positive findings. This study measured physician behavior in terms of referrals, but left open the question of whether the test was used appropriately. If the referring physicians ignored the results (based on past experience, clinical impressions contrary to the EMG report, risk-benefit ratio for treatment options resulting from the test result, financial incentives to the physician, or lack of communi- cation, among other factors), one could contend that too many consults were ordered. On the other hand, if as a result of each of the EMG reports, physicians acted decisively and differently regarding their treatment plan, one would wonder if enough electrodiagnostic consultations were ordered. While a study of referring physician responses to an EMG report is useful in determining the value of EMG, it would have to be very large to reflect the usual practices of different physicians in the commu- nity. The current study controls for that problem by assuming that a change in diagnosis from before testing is the only value of an EMG, and by using a single, experienced specialist to control the quality of the pre-EMG assessment.

There were three hypotheses to this study. The first hypothesis was that for patients referred for electrodiagnostic evaluation of upper extremity nerve complaints, there is a clinically and statistically significant difference between the diagnoses made and diagnostic certainty obtained after a comprehensive


history and physical examination by a competent examiner, and the diagnosis and diagnostic certainty obtained after electrodiagnostic testing performed by that examiner.

Hypothesis 2 was that the number of electrodiagnostic tests (NCS and needle examinations) performed correlates with the medical complexity of the case (specifically with the size of the clinical differential diagnosis, level of certainty about these diagnoses, the subtlety of findings on physical examination, the number of areas of pain indicated on a pain drawing, the number of previous hospitalizations, and the number of medical problems).

The third hypothesis is that final electrodiagnostic conclusions are dependent upon integration of clinical, needle electro- myographic, and nerve conduction information. Specifically, there is an independent relationship between confidence in final diagnosis and confidence in the conclusions reached from each of these three aspects of the consultation.

METHODS Over a ‘I-year period, 255 consecutive patients were evalu-

ated by the same physician, who is Board-certified in both physical medicine and rehabilitation and electrodiagnostic medicine. The first 91 cases were seen in the electrodiagnostic laboratory of a university orthopedics and rehabilitation department. Patients were almost exclusively referred by university faculty subspecialist orthopedic surgeons. The final 164 cases were seen in a private practice setting in a small urban area. This practice setting included a broad referral base ranging from primary care physicians to specialists. All patients com- pleted an extensive codified four-page history form that included medical, surgical, and family histories, review of systems, list of medications and allergies, social history, chief complaint, and pain drawings. Additional history was obtained verbally. The physician recorded an extensive and codified physical examination including: strength testing of all upper extremity muscle groups; reflexes at the biceps, triceps, brachio- radialis, and Achilles tendons; reproduction of tenderness, Spurling’s test, and Tinel’s sign over the median nerve at the wrist and the ulnar nerve at the wrist and elbow. Additional physical examination was performed as needed.

Some clinical data were distilled into group variables. The “number of medical problems” included a summary of all medical problems listed by the physician on the history and physical examination form, regardless of their applicability to the diagnosis in question. For example, a patient who had diabetes, a recent wrist fracture, and a remote history of appendectomy had three medical problems. Similarly the “number of previous hospitalizations” reflected the number of times hospitalized during a lifetime, regardless of cause.

Pain drawings were separated into two variables. One, “number of areas drawn,” summarized the number of body areas that the subject marked as painful. A template that delineated eight body areas (right and left arm, right and left leg, head, neck, trunk, and low back) was placed over the subject’s drawing to determine the number of areas involved. The second variable was “out of body markings.” It was scored as positive or negative, depending on whether the subject drew arrows, wrote any descriptions, or made markings outside of the line figure.

Muscle strength was tested in 17 upper extremity movements on each side, representing all nerve distributions in these extremities. A single variable-“Number of areas of power loss”-was constructed, based on the number of movements with clinical weakness (grade 4 or less).

The physician then listed a differential diagnosis for the patient, using a coded system devised by the AAEM.24 Clinical

VALUE OF ELECTRODIAGNOSTIC CONSULTATION, Haig 1275

confidence for each of the diagnoses was rated on a confidence scale as follows: 0, no comment, or did not test for diagnosis; 1, looked for and found no evidence for diagnosis; 2, nonspecific abnormalities consistent with diagnosis; 3, abnormalities fairly specific to diagnosis; and 4, very strong evidence for diagnosis.

The score of 0 (no comment or did not test for diagnosis) was used in two instances when the initial clinical assessment did not look for a diagnosis subsequently found on EMG. For hypothetical example, a carpal tunnel syndrome referral was made in which the actual final diagnosis of amyotrophic lateral sclerosis was not considered during the history and physical examination. Alternately, a patient may have a neurologic diagnosis demonstrated on physical examination that was not explored during the technical component of the consultation (eg, a person with an old traumatic ulnar neuropathy on examination that was not relevant to the electrical testing for carpal tunnel syndrome, or a patient who declined some component of the testing.) In this situation the confidence score was classified by the initial clinical examination, but subsequently coded as 0 by the severity scale after the electrodiagnostic consultation.

Electrodiagnostic testing was then performed. The extent of testing, including the number of sensory or motor nerve conduction studies performed and the number of extremities or body regions (head, neck, thorax, or lumbar) tested with needle EMG, was based on the clinical judgment of the electromyographer. Individual components of the testing were judged as normal or abnormal based on local laboratory values, most of which conformed with techniques and values contained in Ma and Liveson’s handbo0k.l For each diagnosis, confidence in the supporting evidence obtained in the NCS component and in the EMG component of testing were scored separately and rated according to the same scale of 0 to 4 as above.

A final diagnosis combining the NCS and EMG information was also scored on the same scale and was placed on the medical record; this diagnosis was based on the clinician’s judgment of all of the medical information including history, physical examination, EMG, and NCS data.

The severity of the lesion was also rated using a severity scale of 0 to 5: 0, not considered; 1, very mild, if present at all; 2, mild; 3, moderate; 4, severe, not complete; and 5, complete denervation.

In addition, a variable regarding the value of electrodiagnostic testing was created. This variable was intended to reflect the hypothetical value of changing a diagnosis or its certainty. In constructing this model, we hypothesized the following: (1) The referral sources ordered an electrodiagnostic evaluation because a change in diagnosis or confirmation of a diagnosis would be valuable in management of the patient. (2) Electrodi- agnostic testing might add value to the clinical examination by confirming a previous notion (ruling in a diagnosis previously considered likely or ruling out one considered not likely),

refuting a previous notion (ruling in a diagnosis not considered, or considered unlikely, or ruling out a diagnosis that was previously considered likely), or it may not change the previous notion (nonspecific findings that do not clarify the situation). (3) The findings of the electromyographer are not disputed or disbelieved by the referring physician.

Table 1 shows specifically how this variable was constructed by comparison of different clinical and conclusion confidence scores. For instance, if a patient with “strong evidence” for carpal tunnel syndrome after history and physical examination was subsequently found to have normal NCS and EMG (“no evidence” final diagnosis confidence), the “added value” variable would score “refute.” This model ignores other values of EMG as discussed later, including the value of prognosis or precise localization. It provides an underestimated but func- tional measure of the actual clinical utility of the information gleaned from electrodiagnostic testing.

Data were tabulated and entered into a computer database. Data were checked for errors and then analyzed using the Statistical Package for Social Studies (SPSS).25 Subject demographics and clinical information were calculated. The unit of analysis used in this study included both the patient and diagnosis level data. Each patient may have at least one diagnosis and no more than eight diagnoses.

When using the diagnosis level data (as opposed to patient level data), the multicollinearity problem among the diagnoses belonging to a single patient was recognized but not controlled in this study. In other words, despite the fact that relationships have been documented between different neurologic diagnoses in single subjects, each diagnosis and the data that support it stand alone in the data analysis of diagnostic level data.

The t test was used to compare the difference in the number of reasonably supported diagnoses (diagnostic confidence > 1) based on clinical conclusions and final electrodiagnostic conclusions (hypothesis 1).

Spearman and Pearson correlation analyses were used to test the relation between the amount of electrodiagnostic testing and the medical complexity of the case using the patient level data (hypothesis 2). In addition, the same analyses were used to examine the relations between confidence in clinical and final diagnosis and various clinical parameters and the unit of analysis of this test used the diagnosis level data (hypothesis 3). During these analyses diagnostic certainty codes 0 and 1 were combined and recoded as 1.

Cohen’s kappa analyses were used to examine the relation between confidence in diagnoses based on clinical, EMG, and NCS data with confidence in the final conclusion. The relation between the severity of the lesion and clinical confidence and conclusion confidence (hypothesis 3) was also tested using kappa analyses. The diagnosis level data was used. Cohen’s kappa was used to measure agreement between multiple measurements from each study subject; in this study the kappa

Table 1: The Added Value of Electrodiagnostic Testing

Not Considered 0

Final Diagnosis Confidence

No Evidence Nonspecific Specific Strong Evidence 1 2 3 4

Clinical Confidence 0 1

2 3 4

Confirm Confirm No change Refute Refute Confirm Confirm No change Refute Refute

Refute Refute No change Confirm Confirm Refute Refute No change Confirm Confirm Refute Refute No change Confirm Confirm



statistic was used to examine the relation between the conclusions before and after EMG tests. The kappa coefficient always ranges from - 1 to + 1. A value of 1 indicates perfect agreement; a value of -1 indicates perfect disagreement. A value of 0 indicates that the similarity between the before and after EMG test results is the same as the investigators would expect by chance.

RESULTS Table 2 shows patient demographics. Age and sex reflect a

broad base of referral. As shown in table 3, the diagnoses reflect a distribution of cases typically seen in electrodiagnostic laboratories, with carpal tunnel syndrome, cervical radiculopathy, and ulnar neuropathy the most common diagnoses. The population of patients studied is probably representative of cases in which either a primary care physician or specialist is strongly considering the possibility of an upper extremity nerve disorder.

During this study non-neurologic diagnoses were common as alternative or additional explanations of patients’ symptoms, but were not coded for in most cases, because it was assumed that such diagnoses would be detected by a competent examiner without electrodiagnostic testing. Thus, the diagnosis of “non- neurologic disorder” was coded only sporadically, usually in patients who had negative electrodiagnostic tests.

Hypothesis 1 The primary aim of this study was to determine if electrodiag-

nostic consultation changed the clinical impression about a patient’s diagnosis from that established by a thorough, competent history and physical examination by the same person. The results demonstrated in table 4 were calculated based on the assigned added values of electrodiagnostic testing (table 1) and the confidence scale (table 5). As table 4 demonstrates, electrodiagnostic testing provided information substantially contrary to the clinical impression in 42% of cases. This includes 6.5% of clinical diagnoses supported by what was thought to be fairly specific or very strong evidence, but were ruled out after electrodiagnostic testing, 1.5% of cases where EMG provided strong evidence for a diagnosis that was clinically not considered or not supported, 23% of diagnoses considered probable but without definitive clinical findings that were dismissed after electrodiagnostic testing, and 11% of cases thought to be unclear but found to be clearly positive.

As table 6 demonstrates, for each patient, there were 2.6 2 1.4 clinical differential diagnoses and 1.9 + 1.3 final differential diagnoses. Initially, 2.7% of the subjects were not thought to have any plausible nerve complaint, (confidence <l) but 15.7% had no nerve lesion in their final diagnosis. Electrodiagnostic tests did exclude some clinical differential diagnoses that were rated as “nonspecific abnormalities consistent with diagnosis,” “abnormalities fairly specific to diagnosis,” and “very strong evidence of diagnosis.” The distributions of the number of diagnoses for clinical judgment and final conclusion were shown in figure 1. The results of t test show that the number of diagnoses seriously considered (score > 1) per patient declines substantially after electrodiagnostic testing, thus narrowing the differential diagnosis in many cases.

Hypothesis 2 The process of clinical decision making within the electrodi-

agnostic test was another area of analysis. The relation between diagnostic certainty and the number of NCS performed was inverse (Spearman Y = -.62, p = .lO, N 2 .Ol, with alpha set at .lO). The relation between number of extremities tested (not


Table 2: Subject Demographics and Clinical Information (II = 255)

Age (yrs) Sex (% male)

Number of prior hospitalizations Number of medical problems

listed by patient Presenting complaint

Neck

Right arm Left arm

Bilateral complaints

Duration of symptoms Less than 1 mo

1 to 3mo 3 to 6mo

6mo to lyr 1 to 5yrs

More than 5yrs Patient attributed problems to

Work

Motor vehicle accident Other abrupt onset

Other gradual onset Pain drawing, number of areas

marked Pain drawing, mark(s) outside of

the body

Physical Examination

Number of areas strength lost in physical exam

Tenderness Tinel’s sign Spurling’s sign

Reflex asymmetry Normal exam except tender-

ness Previous tests for this problem

Electrodiagnostic studies X-ray

Advanced radiologic studies* Electrodiagnostic Testing

EMG, number of regions (range, l-8) tested per case

Needle EMG Right upper extremity

Left upper extremity Right lower extremity

Left lower extremity Cranial nerves

NCS (number of studies)

Long latency studies or alternative studies

45.74 t 6.7

38.8% 3.1 L 2.8

3.7 t 3.4

39 (15.3%)

185 (72.5%) 171 (67.1%)

105 (41.2%)

19 (7.8%) 43 (17.6%)

38 (15.5%) 44 (18.0%)

66 (26.9%)

35 (14.3%)

70 (32.6%)

13 (6.0%) 50 (23.3%)

82 (38.1%)

2.1 L 1.0

52 (20.8%)

1.2 ir 2.07 106 (49.3%)

117 (51.1%) 25 (11.1%)

59 (24.2%)

49 (20.3%)

34 (13.9%) 94 (38.5%)

27 (11.1%)

2.8 2 1.43

168 (67.2%)

149 (59.6%) 15 (5.9%)

10 (4.0) 4 (1.6)

4.95 + 3.1 (range,O-14)

.I4 t .60 (range, O-5)

Data presented as the number (and percentage) of subjects respond- ing affirmatively, except where presented as mean ? standard deviation. * Computed tomography, myelogram, magnetic resonance imaging.

muscles tested) and diagnostic certainty was less clear (Spear- man Y = .058, p = .0123, N 2 .Ol). Table 3 demonstrates certainty of electrodiagnostic testing for various presenting diagnoses and table 7 presents different profiles that suggest that the extent of testing varies with the diagnosis considered.

In table 7, the number of NCS and extremities tested with needle EMG were calculated for each diagnostic category. Many patients had more than one diagnosis; thus, the number of


Table 3: Certainty of Electrodiagnostic Testing for Various Presenting Diagnoses

AAEE Code/Rate

Clinical Confidence

0 1 2 3 4 ”

Carpal tunnel syndrome

Polyneuropathy Ulnar neuropathy Focal upper extremity

nerve or plexopathy Cervical radiculopathy

Central nervous system

and muscle disease Lumbar lesion

Non-neurologic disorder

0 7 98 149 28 290 0 14 131 50 2 198 0 9 51 34 7 101

0 9 39 20 10 78

0 2 18 6 0 26

0 6 9 2 2 19

0 0 0 5 0 5 0 0 0 2 1 3

Nerve Conduction Studies

0 1 2 3 4

Carpal tunnel syndrome

Polyneuropathy Ulnar neuropathy

Focal upper extremity nerve or plexopathy

Cervical radiculopathy Central nervous system

and muscle disease Lumbar lesion

Non-neurologic disorder

4 72 30 125 51 21 98 32 32 2

2 38 22 36 3

18 35 11 8 1

9 12 2 2 0

4 7 7 1 0 0 1 1 0 0 2 0 0 0 1

Needle Electromyography

0 1 2 3 4

Carpal tunnel syndrome Polyneuropathy

Ulnar neuropathy Focal upper extremity

nerve or plexopathy Cervical radiculopathy Central nervous system

and muscle disease

Lumbar lesion Non-neurologic disorder

21 149 41 48 13 1 69 67 46 12

6 48 31 12 4

2 39 12 15 9 0 13 4 4 5

0 4 9 5 0

0 0 1 4 0 2 0 0 0 1

Conclusion

0 1 2 3 4

Carpal tunnel syndrome Polyneuropathy

Ulnar neuropathy Focal upper extremity

nerve or plexopathy Cervical radiculopathy

Central nervous system and muscle disease

Lumbar lesion Non-neuroloaic disorder

0 79 31 103 71 1 67 62 55 12

0 34 27 34 6

1 35 13 17 11

0 13 4 6 3

0 5 IO 4 0 0 0 1 4 0 1 0 0 1 1

NCS/EMG for each “overall” diagnosis does not reflect testing for that diagnosis alone. Some patients had only one clinically “significant” diagnostic possibility. Table 7 demonstrates that for each diagnosis where data is available to compare patients, an “isolated complaint” results in fewer NCS and extremity EMG examinations than the same diagnosis when considered among other diagnoses. Data in table 2, for instance, show that

Table 4: The Added Value of Electrodiagnostic Testing

Conclusion

Negative Equivocal Positive

Clinical Negative 3.5% 1.5% 1.5% Equivocal 23.0% 14.0% 11.0% Positive 6.5% 5.0% 33.0%

Data show comparison between clinical certainty and electrodiagnostic certainty regarding 710 diagnoses considered in 255 patients with upper extremity neurologic diagnoses.

among patients referred for neck and upper extremity complaints there were 29 instances where the electrodiagnostician performed a needle examination of the lower extremities or the cranial muscles. No patient with a primary referral question of lower extremity lesion or polyneuropathy was included in this study. Carpal tunnel syndrome or cervical radiculopathy protocols do not require testing of these areas. Some aspect of the clinical information or the electrodiagnostic testing led the consultant to consider polyneuropathy, myopathy, or anterior horn cell disease, any of which might require further explora- tion in the lower extremity or head.

Table 3 reflects the complexity of this process more specifically. (Percentages quoted in this discussion are calculated from data on table 3, but the actual percentages are not listed on that table along with the data to make the table more readable.) For example, when carpal tunnel syndrome was considered, 34% (98/290) of the time clinical information was rated as nonspecific, and almost all other cases had specific or strong clinical evidence. Needle EMG (considered by many not very sensitive for carpal tunnel syndrome) showed no evidence of the disorder in 5 1% (149) of instances. In contrast, NCS was nonspecific in only 11% (30) of cases, with final conclusion reflecting primarily nerve conduction results-IO% (3 1) uncertain, 27% (79) ruled out, and 60% (174) ruled in. For cervical radiculopathy, a different pattern existed: 69% (18/26) of cases presented with clinically nonspecific evidence, and NCS provided evidence in favor of cervical radiculopathy in only 8% (2) of instances, but the final conclusion that 35% (9) of instances had specific or strong evidence for cervical radiculopathy was driven almost exclusively by the needle examination (positive in 35% [9] of cases). One concludes that electrodiagnostic testing clarifies uncertainty in the clinical diagnosis, but that different components of the electrodiagnostic testing weigh differently for different diseases in making a final conclusion.

Table 3 also reflects some other clinical judgments required in electrodiagnostic testing. For example, of 290 cases with clinical evidence for carpal tunnel syndrome, only 282 cases had NCS performed. In eight subjects, either this clinically

Table 5: Comparison Between Clinical Certainty and Electrodiagnostic Certainty Using the Diagnosis Level Data

(n = 710 Diagnoses)

Conclusion Confidence

Not No strong Considered Evidence Nonspecific Specific Evidence

0 1 2 3 4

Clinical Confidence 0 0 0 0 0 0

1 1 24 11 10 1

2 0 165 101 71 9 3 1 44 33 129 60

4 1 0 3 12 34

Data expressed as numbers of cases.



Table 6: Comparison of the Number of Reasonably Supported Diagnoses (Diagnostic Confidence >I) Based On Clinical Conclusions Versus Final Electrodiagnostic Conclusions

0 1

Number of Diagnoses

2 3 4 5 6 7 8

Clinical Judgment n 7 57 66 62 38 17 5 2 1 % 2.7 22.4 25.9 24.3 14.9 6.7 2.0 .8 .4 Mean = 2.6, SD = 1.4

Final Conclusion Gil 40 15.7 67 26.3 79 31 .o 36 14.1 26 10.2 4 1.6 2 .8 1 .4 0.0 0

Mean = 1.9, SD = 1.3

Results of testing the null hypothesis: tvalue, 5.99; 2-tail significance, .OOO (P < .Ol); standard error of difference, ,123; confidence interval for difference, .496-.979.

evident lesion was not relevant to the referral question or the patient refused NCS. Thirty subjects had “nonspecific” NCS findings for carpal tunnel syndrome. In some cases, this was a low amplitude evoked response (which is abnormal, but does not localize a lesion to the wrist). In other cases, the nerve study results were borderline abnormal or multiple nerve studies were in conflict with each other. The consultant chose not to make a definitive decision about these findings.

Another aim of the study was to explore the relations between clinical information and the extent of electrodiagnostic testing. The data presented in table 8 show that as the number of clinical differential diagnoses increases, the number of NCS and muscles tested increases; as the total number of areas indicated on a pain drawing increases, the number of NCS increases; as the total number of hospitalization increases, the number of NCS increases; as the number of medical problems increases, the number of NCS and muscles tested increases; and as the number of areas of power loss indicated increases, the number of NCS decreases and muscles tested increases (though not statistically significant for the latter). Notably, this study did not assess the number of muscles examined with a needle, but only the number of extremities examined. This data suggests that the clinical diagnosis certainty and medical complexity substantially affect the extent of testing.

90

80

70

60

g 50

.E 40

30

20

10

0 012 3 4 5 6 7 8

Number of Diagnoses

Fig 1. The number of diagnoses seriously considered at the time of clinical evaluation (+) and after electrodiagnostic evaluation (W). Note the substantial shift toward fewer diagnoses after consultation.

Hypothesis 3 Subsequent analyses were performed to determine exactly

what factors contributed to diagnostic certainty. Statistical analyses in table 9 show that diagnostic certainty declines when patients present their problems in more complex ways. An increased number of areas marked on a pain drawing correlates with decreased clinical and electrodiagnostic certainty, as does “out of body” markings on pain drawings, which in at least one study suggest a tendency towards somatization.26 The number of areas of strength loss on physical examination positively correlated with the clinical and final electrodiagnostic certainty. The number of previous hospitalizations and the number of medical problems did not reach statistical significance in this regard. The strengths of the relationships in the current study are low, but this may reflect the fact that medical problem lists and pain drawings are relatively insensitive indicators of medical complexity and psychosocial issues. Clinically these relationships make sense. It is difficult to be certain about the diagnosis in patients with complex medical histories, wide- spread complaints, or exaggerated presentations.

The results of Kappa tests show that if the clinical confidence and NCS confidence have the same conclusion, these conclusions can be said to be “concordant” 15% of the time and “discordant” 85% of the time. If the clinical confidence and EMG confidence have the same conclusion, these conclusions can be said to be “concordant” 12% of the time and “discordant” 88% of the time. In addition, the findings suggest that if the clinical confidence and conclusion confidence have the same conclusion, these conclusions can be said to be “concordant” 21% of the time and “discordant” 79% of the time. The extent of agreement between clinical confidence and conclusion confidence is greater than the relation between the clinical confidence and either of the technical components of the electrodiagnostic consultation.

Table 10 provides a distribution of the clinician’s judgment of the severity of the lesion, based on all evidence at the conclusion of the case. In table 11, the Spearman and x2 tests revealed that clinical confidence regarding the diagnosis correlated strongly and significantly with the severity of the lesion, but the relationship was much stronger between final conclusion confidence in the diagnosis and severity. In essence, the more severe the lesion, the more easy it is to determine the diagnosis. The extent of agreement (kappa tests) between final conclusion confidence and the severity of the lesion is greater than the relation between the clinical confidence and the severity of the lesion. If the conclusion confidence and the severity of the lesion have the same impression, these impressions can be said to be “concordant” 47% of the time and “discordant” 53% of the time.



Table 7: Extent of Diagnostic Testing Related to the Number of Differential Clinical Diagnoses (Clinical Diagnostic Certainty > 1) and Final Diagnoses (Final Diagnostic Certainty > 1)

”

Overall

NCS Needle Exam n

Isolated Complaint

NCS Needle Exam

Carpal tunnel 271 Polyneuropathy 181 Ulnar neuropathy 90 Focal nerve/plexus 67 Cervical radiculopathy 24 Central nervous system/muscle disease 13 Lumbar lesion 5 Non-neurologic 3

6.00 (3.00) 5.54 (2.97) 6.30 (2.97)

3.63 (3.27) 2.67 (1.52)

6.23 (4.62)

8.60 (4.56) 2.00 (1.73)

1.49 t.63) 1.56 c.72)

1.31 (.55)

1.28 1.55) 1.58 t.65) 2.00 (1.22)

2.60 (1.34)

1.33 c.58)

44 5.30 (2.87) 1.25 (.49) 15 1.73 (1.39) 1.40 (.63)

3 5.00 (4.00) 1.00 (.OO) 14 2.64 (2.59) 1.07 (.27)

2 .50 (.71) 1 .oo (.OO) 0 0

0

DISCUSSION Many patients present to primary care physicians or special-

ists with upper extremity complaints that may be attributable to nerves. While the history and physical examination provide some level of certainty as to the etiology of a patient’s symptoms, it is possible that electrodiagnostic testing further refines the diagnosis. This study evaluated a population of patients whom referring physicians thought might have a nerve disorder. This study compared the differential diagnosis and strength of confidence obtained from a carefully performed and comprehensive physical examination by a specialist to information subsequently obtained in electrodiagnostic testing. It examined the relations of various elements in the history and physical examination to various elements in the electrodiagnostic testing in making these conclusions.

In this study, all electrodiagnostic studies, histories, and physical examinations were performed by the same physician, Board-certified in both physical medicine and rehabilitation and electrodiagnostic medicine. An alternative method would have separated the person performing the history and physical from the electromyographer. Although there are merits to such an investigation, a competent electrodiagnostic consultation uses information from the history and physical examination to guide the extent and location of electrodiagnostic testing. A study in which, for instance, a blinded electromyographer is handed a differential diagnosis and asked to test a patient without performing a history and physical would likely artificially diminish the utility of the electrodiagnostic testing. Another research method would study the decision-making of multiple physicians, perhaps of different skill levels. The current study sets the stage for such a project, which would require substantial resources.

Within the limits of its method, this study confirms the hypothesis that electrodiagnostic consultation adds consider- ably to clinical decision-making in patients with upper extremity neurologic complaints. The studies by Dillingham18 and Roija” support this contention, though in a less controlled fashion. In our study, up to eight (rarely) items were listed in the

differential diagnosis (for example, it is not unheard of for a patient to present with a real possibility of bilateral carpal tunnel syndrome, ulnar nerve lesion, cervical radiculopathy, or polyneuropathy). The idea of a unifying diagnosis for all of the patient’s complaints is appealing, but often unrealistic. The current study method did not have the electromyographer list non-neurologic clinical diagnoses. Dillingham18 has shown that non-neurologic diagnoses are exceedingly common in patients referred for upper extremity electrodiagnosis. This suggests that the current study underestimates the value of the clinician in detecting the cause of a patient’s “nerve” complaint.

Electrodiagnostic consultation has benefits beyond refuting clinical suspicions. It is difficult to measure the value of objective confirmation of the presence of a lesion that appears clinically obvious (33% of diagnoses in this study) or absence of a lesion in obviously normal persons (3.5%) (see table 4). While some would claim that objectification of a clinically obvious lesion is not cost-effective, others might point out that what is clinically “obvious” is a highly variable concept, subject to the skills and biases of the observer. Legal concerns, among others, support the value of electrodiagnostic consultation in objectifying clinically obvious lesions.

Electrodiagnostic testing is also used to monitor the severity of a lesion, to provide prognosis, to map out the exact location of a lesion for surgical intervention, and to provide some estimate of the age of a lesion that may assist in differentiating current from previous complaints in a similar region. With nerve illnesses, EMG can define the type of pathology (axon loss vs demyelination) and thus provide valuable clues as to the etiology and treatment of the neuropathy. These issues are not addressed in this study. In this regard, we conclude again that the current study greatly underestimates the value of consultation.

Insurers have sought to cut costs and eliminate abuse of EMG by specifying a certain number of NCS and extremity needle examinations for any given diagnosis.27 The evidence

Table 9: Relation Between Confidence in Clinical and Final Diagnosis and Various Clinical Parameters (n = 720)

Table 8: Relation Between the Use of Specific Electrodiagnostic Clinical Final Tests and Clinical Data (n = 255 Patients) Confidence Conclusion

No. of No. of Extremity NCS EMG

No. of differential clinical diagnoses .38” .32* Total no. of pain drawing .18* .04 Total no. of hospitalization .13+ .06 No. of medical problems ,221 .13+ No. of areas of power loss indicated -.23* .16+

* p < .Ol; + p < .05 (Pearson’s correlation).

Number of medical problems -.02 .03 Number of previous hospitalizations -.04 .Ol Number of pain drawing -.11* -.12* “Out of body” pain drawings .07’ .08+ Number of areas of power loss indicated .15” .24*

Clinical confidence and final conclusion were original variables of clinical confidence and conclusion confidence (0 to 4). “Out of body” pain drawings was a dichotomous variable (0, no out of body drawing; 1, at least one out of body drawing). * p < .Ol; + p < .05; * pi .I0 (Spearman correlations).



Table 10: Assessment of Severity of Lesions for Various Conclusion Diagnoses

Severity

AAEE Code 0 12 3 45

Carpal tunnel syndrome 70 22 39 121 27 1 Polyneuropathy 61 31 42 53 1 0

Ulnar neuropathy 33 9 44 IO 3 1 Focal upper extremity nerve or

plexopathy 30 6 13 11 12 1 Cervical radiculopathy 13 3 2 7 10

Central nervous system and muscle disease 544 600

Lumbar lesion 001 400 Non-neurologic disorder 101 001

presented here suggests that the extent of testing relates to several factors other than the referring diagnosis alone.

This study represents the first prospective evaluation of the process of electrodiagnostic consultation in the literature. The conclusions from this study do not stand alone in justifying the use of electrodiagnostic testing or electrodiagnostic consultation. The steps enumerated in the introduction require multiple stages of proof. The current methodology can be refined and should be repeated under other circumstances, with different clinicians, different patient populations, and different measurement tools. It is hoped that this first study demonstrates the ability to measure the phenomena that contribute to the value of a test and a diagnostic consultation, not only in electrodiagnosis, but in other fields of medicine.

The study demonstrates several concepts that are important to understanding the practice of electrodiagnostic medicine:

Even in the optimal circumstance: where the clinical diagnosis is made by a specialist performing a comprehensive clinical evaluation, electrodiagnostic testing changes the clinical diagnosis in a substantial number of cases. Final diagnostic certainty depends on integration of the clinical history and physical examination into a differential diagnosis, and integration of that information with the technical components of the study in ways that are complex and different for different diagnoses. The effort involved in the technical component of electrodiagnostic testing relates not only to the referral diagnosis, but also to other factors such as the complexity of the patient’s medical history and the lack of severity or specificity of the patient’s complaint.

In conclusion, this information leads us to believe that electrodiagnostic consultation is an appropriate referral consideration for patients with upper extremity neurologic complaints. It is

Table 11: Relation Between Severity of Lesions and Clinical and Final Electrodiagnostic Confidence (II = 694 Diagnoses)

Spearman r Kappa x2 df Significance

Clinical confidence with

severity .51” .I6 279.39 15 .oo* Final conclusion confi-

dence with severity .88” .47 990.89 20 .oo*

For the variables of clinical and final conclusion confidence, cateao- ries 0 and 1 in the original scales were recoded into 1, others w&e kept the same (2 = 2, 3 = 3, 4 = 4). The variable of the severity of a lesion was recoded; categories 0 and 1 in the original scales were recoded into 1, categories 4 and 5 were recoded into 4 and others !qq:kq$the same (2 = 2,3 = 3).

1.

2.

3.

4.

5.

6.

I.

8

9.

10.

11.

12.

13.

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difficult to imagine a technician, therapist, or nonspecialist physician making the multiple and complex decisions-which must be based on both a knowledge of disease processes and an understanding of the technical aspects of the testing proce- dures-required to optimize the results of an electrodiagnostic consultation. Payers and providers should proceed with caution in defining the specific components of the electrodiagnostic test that are appropriate for certain referral diagnoses.

Acknowledgment: The author acknowledges Marc Nuwer for manuscript review.

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