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  • 7/27/2019 pruebas laboratorio uci


    Laboratory Testing in the Intensive

    Care Unit

    Michael E. Ezzie, MD, Scott K. Aberegg, MD, MPH,James M. OBrien, Jr, MD, MSc*

    Division of Pulmonary, Allergy, Critical Care, and Sleep Medicine, The Ohio State University

    Medical Center, 201 Davis HLRI, 473 West 12th Avenue, Columbus, OH 43210, USA

    Scope and cost of laboratory testing

    Laboratory testing is ubiquitous among hospitalized patients. Patients in

    intensive care units (ICUs) are subject to a higher number of blood draws,

    resulting in greater blood loss per day and greater phlebotomy during the

    entire hospitalization. Patients with arterial lines; those in teaching ratherthan nonteaching ICUs; and patients with higher severity of illness and spe-

    cific diagnoses, such as sepsis, have more frequent laboratory testing and

    phlebotomy [1,2]. There is also considerable variation in practice between

    physicians [3] and institutions [2]. Laboratory testing is more common early

    after admission with more than one third of laboratory tests performed

    within 24 hours of ICU admission [2]. A relatively small number of tests

    comprise most testing performed. In one study, fewer than 25 tests and pro-

    files accounted for 80% of the laboratory testing in each of three ICUs [4].

    Depending on the ICU, between 104 and 202 tests accounted for 99% of thetotal laboratory testing performed. Table 1 shows the tests and profiles from

    the top 80% of tests that were common to the three studied ICUs. The Ohio

    State University Medical Center charges for each of these tests are also

    shown. The authors experience is that many practitioners are unaware of

    the costs of individual laboratory tests. Although charges are overestima-

    tions of cost and reimbursement, these values also do not include the ex-

    pense incurred through phlebotomy. Providing such cost data to clinicians

    reduces laboratory requests [5].

    This article was supported by NIH/NHLBI grant K23 HL075076 (to J.M. OBrien).

    * Corresponding author.

    E-mail address: [email protected] (J.M. OBrien).

    0749-0704/07/$ - see front matter 2007 Elsevier Inc. All rights reserved.


    Crit Care Clin 23 (2007) 435465

    mailto:[email protected]://[email protected]
  • 7/27/2019 pruebas laboratorio uci


    It is estimated that 10% to 25% of ICU costs are attributable to labora-

    tory testing [6,7]. In a multicenter study of hospitalized patients, many of the

    diagnosis-related groups (DRGs) with the highest per-patient laboratory

    costs likely included an ICU stay (Table 2) [8]. Of the 33 conditions with

    identifiable median ICU costs, 7 had laboratory costs that exceeded other

    costs of ICU care. Regarding national estimates of expenditures, one study

    Table 1

    Common laboratory tests among patients in the ICU and their charges

    Laboratory test ChargeAlkaline phosphatase $32

    Alanine aminotransferase $58

    Arterial blood gas (pH, PCO2, PO2, HCO3, O2saturation, base excess)


    Aspartate aminotransferase $41

    Basic metabolic panel (sodium, potassium, chloride,

    carbon dioxide, anion gap, glucose, blood urea

    nitrogen, creatinine)


    Sodium $28

    Potassium $28

    Chloride $28

    CO2 $32

    Blood urea nitrogen $25

    Creatinine $28

    Glucose $25

    Ionized calcium $132

    Inorganic phosphorus $28

    Magnesium $37

    Bilirubin, total $28

    Bilirubin, direct $32

    Lactate dehydrogenase $39

    Partial thromboplastin time $67

    Prothrombin time/international normalized ratio $58

    Complete blood cell count (white blood cell count,

    red blood cell count, hemoglobin concentration,

    hematocrit, mean corpuscular volume, mean cell

    hemoglobin, mean cell hemoglobin concentration,

    red blood cell distribution width, platelet count,

    mean platelet volume)


    White blood cell count $47

    Hemoglobin $40

    Hematocrit $37Platelet count $44

    White blood cell differential $41

    These are the top 80% of laboratory tests ordered from medical, surgical and pediatric ICUs

    in a single center. Charge data are available at:


    Abbreviations: ALT, alanine aminotransferase; AST, aspartate aminotransferase.

    Adapted from Frassica JJ. Frequency of laboratory test use in the intensive care unit and its

    implications for large-scale data collection efforts. J Am Med Inform Assoc 2005;12:232.

    436 EZZIE et al
  • 7/27/2019 pruebas laboratorio uci


    suggested that $172 million is spent annually on initial testing at level I

    trauma centers for major trauma victims [9]. Considering that more than

    $55 billion is spent on critical care in the United States [10], annual expen-

    ditures for laboratory testing in ICUs are in the range of $5 to $14 billion.

    Table 2

    DRGs with the highest per-patient laboratory costs for patients in the University HealthSys-

    tems Consortium database


    Median costs,


    Median percentage

    of total costs

    Liver transplant 8329 10.7

    Heart transplant 6859 8.0

    Bone marrow transplant 5928 9.4

    Lung transplant 5260 7.6

    Extensive burns with

    operating room


    4294 5.7

    Craniotomy for multiple

    significant trauma

    3750 8.1

    Acute leukemia without

    major operating room

    procedure, ageO17 years

    3693 12.1

    Malignant breast disorders

    with complications or


    2221 8.9

    Kidney transplantation 2086 4.9

    Acute leukemia without

    major operating room

    procedures, age 017


    1822 18.3

    HIV with extensive

    operating room


    1780 13.6

    Extreme immaturity or

    respiratory distress,


    1749 5.1

    Respiratory system

    diagnosis with ventilatory


    1705 9.7

    Cardiac valve procedurewith cardiac


    1644 5.3

    Pancreas, liver, and shunt

    procedures with

    complications or


    1620 9.8

    Coronary bypass with

    cardiac catheterization

    1563 6.8

    Adapted from Young DS, Sachais BS, Jefferies LC. Laboratory costs in the context of dis-

    ease. Clin Chem 2000;46:970; with permission.


  • 7/27/2019 pruebas laboratorio uci


    Recent data demonstrate that patients cared for by physicians who spend

    more money on laboratory tests do not have better outcomes [3]. Among

    patients cared for by intensivists with the highest discretionary spending,laboratory costs were $273 higher per ICU stay than among the lowest

    spenders. The highest spenders also spent more on other discretionary costs,

    which could be driven by increased laboratory use, including pharmacy

    costs (eg, potassium supplementation for potassium levels outside of the

    reference interval) and blood banking costs (eg, red blood cell transfusion

    in a patient with anemia attributable to laboratory testing). Patients cared

    for by physicians who spent more did not have significantly different

    ICU lengths of stay (adjusted P .32) or hospital mortality (adjusted

    P .83). As with physicians, institutions with more frequent blood testingpractices do not have lower associated hospital mortality (r 0.003,

    P .98) [2].

    Reference intervals and what is normal

    In most instances, a reference interval is developed from a cohort of in-

    dividuals without apparent disease. All members of the cohort undergo test-

    ing, and the central 95% of the results are determined. Therefore, bydefinition, 5% of a normal population has test results outside of the ref-

    erence interval. There is an obvious limitation in equating values outside of

    this range to the presence of disease. In addition, considerations of inherent

    biologic variation, interindividual differences, and the validity of using ref-

    erence intervals generated on a different population to patients undergoing

    clinical evaluations are often ignored. These may be of particular relevance

    when considering laboratory testing in ICU populations.

    In some instances, clinical laboratories provide comparison values that

    have diagnostic, therapeutic, or prognostic implications instead of being de-rived from reference intervals. For example, 21% of adults have a blood

    cholesterol level of at least 240 mg/dL [11]. Such a level carries an increased

    risk of cardiovascular events, and reduction of cholesterol levels is associ-

    ated with a reduced risk [12]. Instead of providing the central 95% of cho-

    lesterol values in the population, it is more instructive to provide values

    driven by evidence of higher risk. Clinicians are not interested if a patients

    cholesterol is abnormal relative to a healthy population but, instead, if