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Functional gait assessment and balance evaluationsystem test: Reliability, validity, sensitivity, andspecificity for identifying individuals withParkinson disease who fallAbigail L. LeddyWashington University School of Medicine in St. Louis

Beth CrownerWashington University School of Medicine in St. Louis

Gammon M. EarhartWashington University School of Medicine in St. Louis

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Recommended CitationFunctional gait assessment and balance evaluation system test: reliability, validity, sensitivity, and specificity for identifying individualswith Parkinson disease who fall. Leddy AL, Crowner BE, Earhart GM. Phys Ther. 2011 Jan;91(1):102-13. doi: 10.2522/ptj.20100113

doi: 10.2522/ptj.20100113Originally published online November 11, 2010

2011; 91:102-113.PHYS THER. EarhartAbigail L. Leddy, Beth E. Crowner and Gammon M.Disease Who FallSpecificity for Identifying Individuals With ParkinsonSystem Test: Reliability, Validity, Sensitivity, and Functional Gait Assessment and Balance Evaluation

http://ptjournal.apta.org/content/91/1/102found online at: The online version of this article, along with updated information and services, can be

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Functional Gait Assessment andBalance Evaluation System Test:Reliability, Validity, Sensitivity, andSpecificity for Identifying IndividualsWith Parkinson Disease Who FallAbigail L. Leddy, Beth E. Crowner, Gammon M. Earhart

Background. Gait impairments, balance impairments, and falls are prevalent inindividuals with Parkinson disease (PD). Although the Berg Balance Scale (BBS) canbe considered the reference standard for the determination of fall risk, it has a notedceiling effect. Development of ceiling-free measures that can assess balance and aregood at discriminating “fallers” from “nonfallers” is needed.

Objective. The purpose of this study was to compare the Functional Gait Assess-ment (FGA) and the Balance Evaluation Systems Test (BESTest) with the BBS amongindividuals with PD and evaluate the tests’ reliability, validity, and discriminatorysensitivity and specificity for fallers versus nonfallers.

Design. This was an observational study of community-dwelling individuals withidiopathic PD.

Methods. The BBS, FGA, and BESTest were administered to 80 individuals withPD. Interrater reliability (n�15) was assessed by 3 raters. Test-retest reliability wasbased on 2 tests of participants (n�24), 2 weeks apart. Intraclass correlation coeffi-cients (2,1) were used to calculate reliability, and Spearman correlation coefficientswere used to assess validity. Cutoff points, sensitivity, and specificity were based onreceiver operating characteristic plots.

Results. Test-retest reliability was .80 for the BBS, .91 for the FGA, and .88 for theBESTest. Interrater reliability was greater than .93 for all 3 tests. The FGA and BESTestwere correlated with the BBS (r�.78 and r�.87, respectively). Cutoff scores toidentify fallers were 47/56 for the BBS, 15/30 for the FGA, and 69% for the BESTest.The overall accuracy (area under the curve) for the BBS, FGA, and BESTest was .79,.80, and .85, respectively.

Limitations. Fall reports were retrospective.

Conclusion. Both the FGA and the BESTest have reliability and validity for assess-ing balance in individuals with PD. The BESTest is most sensitive for identifyingfallers.

A.L. Leddy, BS, is a DPT student inthe Program in Physical Therapy,Washington University School ofMedicine, St Louis, Missouri.

B.E. Crowner, PT, DPT, NCS, MPPA,is Division Director of Clinical Prac-tice and Assistant Professor ofPhysical Therapy and Neurology,Program in Physical Therapy,Washington University School ofMedicine.

G.M. Earhart, PT, PhD, is AssistantProfessor of Physical Therapy,Anatomy & Neurobiology, andNeurology, Program in PhysicalTherapy, Washington UniversitySchool of Medicine, Campus Box8502, 4444 Forest Park Blvd, StLouis, MO 63108 (USA). Addressall correspondence to Dr Earhartat: earhartg@wusm.wustl.edu.

[Leddy AL, Crowner BE, EarhartGM. Functional Gait Assessmentand Balance Evaluation SystemTest: reliability, validity, sensitivity,and specificity for identifying indi-viduals with Parkinson disease whofall. Phys Ther. 2011;91:102–113.]

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Parkinson disease (PD) is a neu-rodegenerative disease that pre-sents a constellation of systemic

motor and non–motor signs andsymptoms. Postural instability, oneof the most disabling cardinal signsof PD, is one of the primary reasonswhy someone with PD may be re-ferred for physical therapy.1,2 Axialsymptoms, such as balance impair-ments, are one of the main predic-tors of quality of life for individualswith PD and have been shown toincrease fall risk.1,3 Up to 68% of in-dividuals with PD will fall in a 1-yearperiod, which can lead to injury andlarge personal and societal costs.4,5

Ideally, individuals with PD whohave impaired balance and an in-creased risk for falls would be iden-tified prior to a fall and an appropri-ate, proactive intervention instated.At the present time, however, thebest predictor of falling is a history ofprior falls.4,6–9 Although many differ-ent balance assessments currentlyare being used, the Berg BalanceScale (BBS) can be considered a ref-erence standard for assessing bal-ance in people with PD, as it is oneof the most commonly used balanceassessments in the clinic and in re-search. The BBS, however, has beenshown to have a ceiling effect in in-dividuals with PD, as well as otherpopulations.10–13 A ceiling effect oc-curs when the highest score on thescale does not capture or discrimi-nate between differences in the up-per end of the attribute being mea-sured. In this case, individuals canreceive a perfect score on the BBSyet still have balance impairmentsthat need to be addressed. A balanceassessment is needed for individualswith PD that can be used to: (1) ac-curately assess balance throughoutthe full ambulatory spectrum of PDand (2) identify who is at an in-creased risk of falling. This study in-vestigated the properties of 2 tests,the Functional Gait Assessment(FGA) and the Balance Evaluation

Systems Test (BESTest), with respectto these 2 criteria.

The FGA is an ambulation-based bal-ance test originally proposed to as-sess higher-level balance in individu-als with vestibular impairments.14

The precursor of the FGA was theDynamic Gait Index (DGI), whichwas validated in various popula-tions,15,16 yet had a potential ceilingeffect.15–17 The FGA has excellent in-terrater reliability (intraclass correla-tion coefficient [ICC]�.93) in inde-pendently living individuals betweenthe ages of 40 and 89 years.18 It alsohas acceptable interrater reliabilityand test-retest reliability (ICC�.86and ICC�.74, respectively) in indi-viduals with vestibular disorders.14

The FGA includes tasks that requiremany postural adjustments, as op-posed to the more static items in theBBS. The reliability of this assessmentfor people with PD is unknown.

The assessment of balance and riskof falling in people with PD by usinga combination of different measuresis well supported in the literature.6,19–22

The Balance Evaluation SystemsTest (BESTest) is a newly developed,multifaceted approach to assessingbalance that combines portions ofdifferent balance assessments.23 Sev-enteen of the 36 items in the BESTesthave been adopted from the fol-lowing previously validated balanceassessments: BBS, DGI, single-limbstance test, Timed “Up & Go” Test,24

Functional Reach Test,25 and modi-fied Clinical Test of Sensory Interac-tion on Balance.26 The remaining 19novel items include a dual-task item,postural response and compensatorystepping items, general alignment instanding, functional strength in thehips and ankles, leaning and returningto vertical, sitting on the ground andreturning to a standing position, andstanding on an incline. All items aredivided into 6 categories (ie, “Biome-chanical Constraints,” “Stability Limitsand Verticality,” “Anticipatory Postural

Adjustments,” “Postural Responses,”“Sensory Orientation,” and “Stabilityin Gait”), each representing a theoret-ical control system for balance.23 Thecategories are theorized to help guideand focus balance interventions oncebalance impairments are identified.The BESTest has been shown to haveexcellent interrater reliability (ICC�.91) and moderate validity with anindividual’s self-perceived balance (r�.636) when used to assess a mixedpopulation of individuals with andwithout disease (including 3 individu-als with PD).23

To assess the validity of these newassessments, previously validatedmeasures of balance and postural in-stability were used. Although theBBS is the reference standard, wecompared the FGA and BESTest withthis tool, as well as other correlatesof postural stability and fall risk, inorder to assess their possible superi-ority. Both disease severity and fearof falling are highly associated withpostural instability and falls.7,27,28

Therefore, the modified Hoehn andYahr scale, the Movement DisordersSociety revision of the Unified Par-kinson’s Disease Rating Scale (MDS-UPDRS), the MDS-UPDRS part 3 (mo-tor examination) (MDS-UPDRS-3),and the Activities-specific BalanceConfidence Scale (ABC) were usedto assess the validity of FGA andBESTest scores.29,30

The MDS-UPDRS total score and theHoehn and Yahr scale are the mostcommonly used assessments of dis-ease severity for individuals with PD.

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The MDS-UPDRS-3 is the motor sec-tion subscale of the MDS-UPDRS thathas been shown to measure motorimpairment, disease severity, anddisability.29,31 The ABC is a question-naire that measures individuals’ self-perceived confidence in their bal-ance. It has been shown to correlatewith postural instability and is pre-dictive of falls in individuals withPD.6,20

The goal of this study was to eval-uate reliability, validity, sensitivity,and specificity for identifying “fall-ers” versus “nonfallers” for the FGAand BESTest in individuals with idio-pathic PD. We hypothesized that theFGA and the BESTest would be reli-able assessments of balance in PDand would correlate well with theBBS, Hoehn and Yahr scale, MDS-UPDRS, MDS-UPDRS-3, and ABC.We also hypothesized that the FGAand BESTest would be able to differ-entiate between individuals who fall

and individuals who do not fall. Fur-thermore, we hypothesized that theBESTest would be more sensitiveand specific in determining fallersversus nonfallers because it is a morecomprehensive test than either theFGA or the BBS.

MethodParticipantsEighty-two individuals with idio-pathic PD were evaluated using theBBS, FGA, and BESTest. All partici-pants met the following inclusion cri-teria: (1) �40 years of age, (2) diag-nosed with idiopathic PD, (3) Hoehnand Yahr scale stage I to IV, (4) com-munity dwelling, and (5) able to pro-vide informed consent and follow in-structions. Individuals were excludedfrom the study due to atypical parkin-sonism or prior surgical managementof PD (pallidotomy or deep brainstimulation).

A list of individuals with PD in the StLouis area who had been evaluatedat the Washington University Schoolof Medicine’s Movement DisordersCenter, stratified by Hoehn and Yahrscale stage, was used for recruit-ment. Individuals were called using arandom number generator after ver-ifying inclusion and exclusion crite-ria via the database. Once contacted,the inclusion and exclusion criteriawere re-verified. Individuals in the StLouis community who heard of thestudy from other participants or theVolunteers for Health database wereallowed to participate as well. Ofthe 82 individuals who agreed toparticipate in the study, 2 wereeliminated based on exclusion cri-teria and an unrelated illness, re-spectively. Twenty-five participants(31.3%) were considered to be fall-ers, which was defined as someonewho reported 2 or more falls in theprior 6 months.

Testing ProcedureEvaluations were performed in a lab-oratory setting at the University ofWashington School of Medicine be-tween July and December 2009. Thestudy was approved by the HumanResearch Protection Office. Partici-pants were instructed to take theirmedication according to their nor-mal regimen and were tested whileon medication. After signing the ap-proved consent forms, participantscompleted demographic informa-tion, reported number of falls in theprior 6 months, and took the ABCwith the assistance of a caregiver asneeded. The balance tests were per-formed in the following order: BBS,FGA, and BESTest. Any test item thatwas duplicated between the testswas performed only once and thenscored using criteria from each test.For example, the sit-to-stand maneu-ver is an item in both the BBS andBESTest, so each participant per-formed it once, but raters gradedthat performance using both the BBSand BESTest criteria. Participants

The Bottom Line

What do we already know about this topic?

People with Parkinson disease (PD) experience more falls and demon-strate increased balance deficits compared with people of the same agewho do not have PD. The balance tests currently used in practice mightnot adequately identify these deficits and fall risk.

What new information does this study offer?

This study verifies that, because of a ceiling effect, the Berg Balance Scale,a popular balance measure, might not identify all people with PD who areat risk for falls or who have balance deficits. The Balance EvaluationSystems Test and Functional Gait Assessment—alternative tests with es-tablished reliability and validity—are now available for use in measuringbalance in people with PD. Each of the tests can differentiate betweenpeople with PD who have fallen and people with PD who have not fallenbetter than the Berg Balance Scale.

If you’re a patient, what might these findings meanfor you?

Using these new outcome measures, physical therapists may be betterable to determine your fall risk.

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performed the tests with shoes off,as required for the BESTest, unlessthey expressed discomfort withoutshoes. Participants were allowed torest as needed during all portions ofthe evaluation. The full test session,including physical evaluations andquestionnaires, required a total ofapproximately 2 hours to com-plete, with balance tests adminis-tered during the first hour. No par-ticipants indicated any wearing offof medication during the balancetesting.

The BBS is a 14-item test, with eachitem rated from 0 (signifying poorbalance) to 4 (signifying better bal-ance). A perfect score is 56. The BBSwas administered as described in theoriginal article,32 with one modifica-tion. The position for the forwardreach item of the BBS was alteredslightly by requiring the participantto raise both arms to 90 degrees andkeep the heels on the floor duringthe reach to further standardize thetest.

The FGA is a 10-item walking-basedbalance test, with each item scored 0to 3. The FGA was administered asdescribed in the original article.14 Itincludes walking forward, backward,with eyes closed, stepping over ob-stacles, changing gait speeds, withdifferent head turns, and with a nar-row base of support. A higher totalscore signifies better balance, with amaximum score of 30.

The BESTest consists of 36 itemsgraded on a 0 to 3 scale, with highernumbers signifying better balanceand a maximum of 108 points. Thetotal score was converted into a per-centage score. The BESTest was per-formed as described by Horak et al,23

with a few slight modifications. Twotrials of the compensatory steppingitems were performed to encouragethe participant to lean adequatelyand to allow the tester to adjust theirpressure as needed. Only the second

trial was scored. One trial, as op-posed to the 2 trials in the originaldescription, was performed for eachof the items in the “Sensory Orienta-tion” category and the functionalreaches due to time constraints. Al-though the BESTest allows for eitherrandom number generation orcounting backward by 3s in thetimed get-up-and-go dual-task item,random number generation wasused for all evaluations.

The 16-item ABC was administeredas a questionnaire. The ABC quanti-fies an individual’s perceived abilityto maintain his or her balance underdifferent circumstances, using ascale of 0% (no confidence) to 100%(total confidence).30

The MDS-UPDRS was followed ac-cording to Goetz et al29 and was ad-ministered by a trained rater. Thetotal MDS-UPDRS score is the mostcommon method of evaluating theseverity of PD across behaviors, ac-tivities of daily living, motor abilities,and other complications of PD. TheMDS-UPDRS-3 is a measure of sever-ity of PD, as well as physical disabil-ity, and includes measures of rigidity,gait, tremor, hand/arm and leg move-ments (bradykinesia), speech, andfacial expressions.31 The modifiedHoehn and Yahr scale also was usedto evaluate disease severity.33

ReliabilityInterrater reliability was determinedusing 3 raters (1 physical therapiststudent and 2 physical therapists)and a subset of 15 participants (meanMDS-UPDRS score�74.2, SD�18.6;mean disease duration�6.8 years,SD�3.26; 20% [n�3] fallers; Hoehnand Yahr scale stage 1�2, stage 2�7,stage 2.5�3, stage 3�2, and stage4�1). The physical therapist studenthad completed 2 years of a Doctor-ate of Physical Therapy program, andthe physical therapists had 13 and 21years of experience, respectively.Raters used the training provided

with each test, which included read-ing instructions for all 3 tests andwatching the item-by-item trainingvideo provided with the BESTest. All3 raters had prior experience usingthe BBS, but no experience usingeither the FGA or the BESTest. Theraters observed one individual with-out PD perform the tests prior toparticipant testing without discuss-ing the rating scales so they wouldbe familiar with the flow of testing.No discussion of the rating scale waspermitted in order to allow the reli-ability to be generalized to individualclinicians performing the tests. Thetest was administered by one of theraters, and all raters concurrently ob-served and rated the participant’sperformance. Raters were allowed toposition themselves as they felt nec-essary. If an item was missed by arater, the item was performed again,and the second trial was rated by allraters. The scores given on the itemsand how to score the items were notdiscussed.

Test-retest reliability was determinedby testing 24 participants (meanMDS-UPDRS score�71, SD�21.9;mean disease duration�6.9 years,SD�3.38; 21% [n�5] fallers; Hoehnand Yahr scale stage 1�2, stage2�11, stage 2.5�6, stage 3�3, andstage 4�2) twice with a 2-week(range�11–16 days) interveningperiod. For both evaluations, par-ticipants were tested at the sametime of day and instructed to takemedications as usual to reduce thelikelihood of on/off medication fluc-tuations causing variations in PDsigns and symptoms. Test-retest reli-ability was determined for a physicaltherapist and the physical therapiststudent.

Once the reliability for all tests wasdetermined to be good using theinitial subset of participants, the re-maining balance evaluations for as-sessing validity, sensitivity, and spec-ificity for detecting fallers versus

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nonfallers were performed by thephysical therapist student.

Data AnalysisStatistics were calculated usingSPSS for Windows (version 17.0).*Independent-sample t tests andMann-Whitney U tests were used tocompare age, disease duration, anddisease severity of the fallers andnonfallers. Interrater and test-retestreliability were calculated using ICC(2,1) because raters tested partici-pants using information that anyphysical therapist or physical thera-pist student would have available.To quantify validity, the correla-tions between the 2 newer testsand commonly used measures ofPD severity and balance were used.The FGA and BESTest were com-pared with the BBS, ABC, MDS-UPDRS, MDS-UPDRS-3, and Hoehnand Yahr scale stages using Spear-man correlation coefficients. Forall Spearman correlations, .00 to.25�little to no relationship, .25 to.50�fair, .50 to .75�moderate, and.75 to 1.00�high correlation. Tomaintain an alpha level of .05, aBonferroni correction for multiplecomparisons required a P value of�.002. Receiver operating charac-teristic (ROC) plots were made foreach test, and cutoff values werechosen by selecting the score withthe minimal value of:

�1 � sensitivity�2 �

�1 � specificity�2,

which maximizes sensitivity andspecificity.34 To allow a more accu-rate comparison with prior studiesidentifying individuals with PD whowere fallers, an alternative cutoffpoint also was calculated by maxi-mizing sensitivity and minimizingnegative likelihood (LR�) ratio. Post-test probabilities were calculated us-

ing LR�, positive likelihood ratios(LR�), and the pretest probabilityof falling from this study sample toallow the balance test results to beinterpreted more completely.35 Over-all accuracy for each balance testwas assessed using the area underthe curve (AUC). The AUC is theprobability that the individual withPD who is a faller will be correctlyidentified, given 2 randomly selectedindividuals are chosen, 1 who is afaller and 1 who is not a faller.36 ForAUC analysis, 0.5�test due tochance, 0.5 to 0.7�low accuracy,0.7 to 0.9�moderate accuracy, 0.9to 1.0�high accuracy, and 1.0�aperfect test.34,36

Sample size calculations for thestudy were based on a power of0.80 and an alpha level of .05. Inter-rater reliability based on 3 raters, anull ICC of .50, and an acceptablereliability of .80 required 15 partici-pants.37 Test-retest reliability basedon 2 trials of testing required 22participants. Eighty-one participantswere required for sensitivity, speci-ficity, and ROC curves by estimatinga 30% faller rate, a confidence inter-val width of 0.20, and a 95% confi-dence level.38

Role of the Funding SourceThis work was directly funded by agrant from the Davis Phinney Foun-* SPSS Inc, 233 S Wacker Dr, Chicago, IL

60606.

Table 1.Participant Demographic and Disease Severity Information Overall and SeparatedOut by Fallers and Nonfallers

CharacteristicOverall(N�80)

Fallers(n�25)

Nonfallers(n�55)

Male (%) 59 64 56

Age (y)

X 68.2 68.8 67.9

SD 9.3 7.8 10.0

Range 45–88 55–88 45–85

Disease duration (y)

X 8.5 11.4 7.15

SD 0.54 5.5a 3.81

Range 1–25 4–25 1–16

MDS-UPDRSb total score

X 72.6 93.8 62.9

SD 25.1 23.1a 19.0

Range 25–135 46–135 25–103

Hoehn and Yahr scale stage

X 2.45 2.9 2.3

SD 0.64 0.71 0.50

Median 2.5 3.0a 2.0

Stage 1 4 1 3

Stage 2 27 1 26

Stage 2.5 30 10 20

Stage 3 13 8 5

Stage 4 6 5 1

a Statistically significant difference between fallers and nonfallers (P�.001).b MDS-UPDRS�Movement Disorders Society revision of the Unified Parkinson’s Disease Rating Scale.

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dation and grant UL1 RR024992 andsub-award TL1 RR024995 from theNational Center for Research Re-sources (NCRR), a component of theNational Institutes of Health (NIH),and NIH Roadmap for Medical Re-search. The funding source had no

impact or input on the design, con-duct, or reporting of this study.

ResultsThe subgroup of fallers was statis-tically different from the nonfallersin disease duration, MDS-UPDRS

scores, and Hoehn and Yahr scalestaging, with the fallers having moreadvanced PD (Tab. 1). The BBSscores were significantly left skewed(Kolmogorov-Smirnov test, P�.035),with 10% (n�8) having a perfectscore (including 1 faller) and 45%(n�36) scoring within the top 10%of the test (including 5 fallers). Thesame 8 individuals who received aperfect score on the BBS showedvarying levels of balance impair-ments on the FGA and BESTest, hav-ing scores ranging from 23 to 30 onthe FGA and from 82% to 94% on theBESTest. The test scores were nor-mally distributed for the FGA and theBESTest. Only 1.3% (n�1) scoredperfectly on the FGA, with 13%(n�10) within the top 10% of thetest, none of whom were fallers.There were no perfect scores on theBESTest, with only 6.4% (n�5) scor-ing in the top 10%, none of whomwere fallers (Fig. 1).

Interrater reliability among the 3 rat-ers was excellent and comparablefor all 3 tests, with ICCs greater than.93 (Tab. 2). Test-retest reliabilitywas similar between the physicaltherapist student and the licensedphysical therapist for both the BBS,which showed moderate reliability,and the BESTest, which had high re-liability. There was a larger discrep-ancy between the test-retest scoresfor the FGA, with the physical ther-apist having excellent reliability, butthe physical therapist student hav-ing only moderately good reliability.The BESTest had the highest test-retest reliability of the 3 assessments(Tab. 2).

The FGA was highly correlated withthe BBS and moderately correlatedwith the ABC and disease severitymeasures, including MDS-UPDRS,MDS-UPDRS-3, and Hoehn and Yahrscale stage. The BESTest was highlycorrelated with the BBS, ABC, MDS-UPDRS, and MDS-UPDRS-3. It was

Figure 1.Distribution of scores for the Berg Balance Scale (BBS), Functional Gait Assessment(FGA), and Balance Evaluation Systems Test (BESTest). K-S�one-sample Kolmogorov-Smirnov Test.

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moderately correlated with Hoehnand Yahr scale stage (Tab. 3).

Receiver operating characteristicplots for the BBS, FGA, and BESTestare shown in Figure 2. The cutoffscores suggested based on maximiz-ing both sensitivity and specificitywere 47/56 for the BBS, 15/30 forthe FGA, and 69% for the BESTest(Tab. 4). Based on these cutoffpoints, similar specificity was found

for all 3 tests, with sensitivity beinghighest for the BESTest. The BESTesthad the highest LR� and the lowestLR�. The pretest probability of be-ing a faller in this study sample was31%. The posttest probability for anindividual to be a true faller based onthese cutoff scores ranged from 56%for the BBS to 61% for the BESTest,given a positive test (identified as afaller), and from 15% on the BBS to

9% on the BESTest, given a negativetest (identified as a nonfaller) (Tab. 4).

When sensitivity was maximized andLR� was minimized, the specificitydecreased for all of the tests (0.19–0.47), and sensitivity increased to0.92 to 1.0. The posttest probabilityfor an individual to be a true fallerbased on these cutoff scores rangedfrom 36% for the FGA to 44% for theBBS, given a positive test (identifiedas a faller), and from 7% on the BBSto 0% on the FGA or BESTest, given anegative test (identified as a non-faller) (Tab. 4).

The nonparametric AUC was calcu-lated because the BBS scores werenot normally distributed. The AUCwas highest for the BESTest, thoughthe 95% confidence interval over-lapped among the 3 tests (Tab. 4). All3 tests showed moderate accuracy.There were no adverse events duringthe course of the study.

DiscussionMeasures that can be used to assessbalance across the ambulatory spec-trum of PD and decipher who is andis not at risk for falling are of vital

Table 2.Interrater and Test-Retest Reliability for the Berg Balance Scale (BBS), Functional GaitAssessment (FGA), and Balance Evaluation Systems Test (BESTest)a

Type of Reliability

BalanceAssessment

Measure Testers ICC (2,1) 95% CI

Interrater reliability (n�15) BBS 2 PTs, 1 SPT .95 .88–.98

FGA 2 PTs, 1 SPT .93 .84–.98

BESTest 2 PTs, 1 SPT .96 .89–.99

Test-retest reliability (n�24) BBS SPT .79 .57–.90

PT .80 .60–.91

FGA SPT .80 .58–.91

PT .91 .80–.96

BESTest SPT .91 .80–.96

PT (n�23) .88 .72–.95

a All intraclass correlation coefficients (ICCs) were significant, with P values of �.01. PT�physicaltherapist, SPT�physical therapist student.

Table 3.Validity (Spearman r) of the Functional Gait Assessment (FGA) and Balance Evaluation Systems Test (BESTest) With Measures ofDisease Severity (Hoehn and Yahr Scale, Movement Disorders Society Revision of the Unified Parkinson’s Disease Rating Scale[MDS-UPDRS], and Movement Disorders Society Revision of the Unified Parkinson’s Disease Rating Scale Part 3 [MotorExamination] [MDS-UPDRS-3]), Self-Perceived Balance (Activities-specific Confidence Scale [ABC]), and the Balance ReferenceStandard (Berg Balance Scale [BBS])a

Disease Severity

Self-PerceivedBalance

Confidence

BalanceReferenceStandard

NewBalance

Measures

ModifiedHoehn andYahr Scale

MDS-UPDRS-3Score

MDS-UPDRSScore ABC Score BBS Score

FGAScore

BESTestScore

Self-PerceivedBalance

ABC Score(N�80)

�.591 �.523 �.726 1.000

Balance ReferenceStandard

BBS Score(N�80)

�.629 �.710 �.710 .638 1.000

New BalanceMeasures

FGA Score(n�79)

�.670 �.669 �.692 .707 .783 1.000

BESTest Score(n�79)

�.736 �.758 �.780 .757 .873 .882 1.000

a All correlations were significant at P�.001 (2-tailed).

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importance to determine appropri-ate treatment for individuals withPD. Early interventions may preventor decrease the negative effects of

postural instability.39–41 This studydemonstrates that both the FGA andBESTest are reliable and valid mea-sures of balance in PD, with accept-

able sensitivity and specificity foridentifying fallers versus nonfallers.

ReliabilityThe high interrater reliability for theBBS, FGA, and BESTest found in thisstudy should be generalizable, astraining for each test included onlyresources available in the clinical set-ting. The video training for theBESTest was used and is availablefor purchase online. The interraterreliability was comparable to whathas been reported for the FGA andBESTest in prior studies with otherpopulations.18,23

Test-retest reliability quantifies thedifference between 2 test sessions,including variability in the tester’srating and the participant’s perfor-mance. Test-retest reliability wassimilar for the physical therapist(ICC�.80) and the physical therapiststudent (ICC�.79) for the BBS, yetlower than in prior studies. Steffenand Seney12 and Lim et al19 reportedICCs of .94 and .87, respectively, inindividuals with PD. One reason forthis difference might be the longertime between test sessions (2 weeks)in our study. Variations in perfor-mance due to medication schedule

Table 4.Cutoff Points With Associated Sensitivity, Specificity, Likelihood Ratios, Posttest Probabilities, and Area Under the Curve (AUC) ofthe Receiver Operating Characteristic Plot for the Berg Balance Scale (BBS), Functional Gait Assessment (FGA), and BalanceEvaluation Systems Test (BESTest)a

BalanceAssessment

Measure AUC (95% CI) Score Sensitivity Specificity LR� (95% CI) LR� (95% CI)

PosttestProbabilityWith Test< Cutoff

Value

PosttestProbabilityWith Test> Cutoff

Value

BBS 0.79 (0.68–0.91) �47/56* 0.72 0.75 2.83 (1.69–4.73) 0.38 (0.20–0.72) 56.3% 14.6%

�52/56 0.92 0.47 1.74 (1.32–2.30) 0.17 (0.04–0.66) 44.2% 7.1%

FGA 0.80 (0.69–0.90) �15/30* 0.72 0.78 3.24 (1.86–5.65) 0.36 (0.19–0.69) 59.6% 14.1%

�27/30 1.00 0.19 1.23 (1.08–1.39) 0.00 (unable tocalculate)

35.8% 0.0%

BESTest 0.85 (0.77–0.94) �69%* 0.84 0.76 3.49 (2.11–5.77) 0.21 (0.09–0.52) 61.3% 8.7%

�84% 1.00 0.39 1.64 (1.32–2.02) 0.00 (unable tocalculate)

42.7% 0.0%

a For all balance tests, 2 cutoff values are reported. The first cutoff value (indicated by asterisk) was chosen to maximize both sensitivity and specificity. Thesecond cutoff value was chosen by maximizing sensitivity and negative likelihood ratio (LR�). Pretest probability for being a faller was 31.3%.CI�confidence interval, LR��positive likelihood ratio.

Figure 2.Receiver operating characteristic plot for the Berg Balance Scale (BBS), Functional GaitAssessment (FGA), and Balance Evaluation Systems Test (BESTest). A black box showsthe cutoff values chosen for each test by maximizing sensitivity and specificity. An Xshows the cutoff value chosen by maximizing sensitivity and minimizing negativelikelihood ratio.

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were controlled for by keeping test-ing at the same time of day; how-ever, it is possible that participantsvaried slightly in their medicationregimen, causing changes in individ-ual performances.

Test-retest reliability for the BESTestwas high and similar for the physicaltherapist and the physical therapiststudent. Despite its complexity andgreater number of items, the BESTestcan be used successfully and consis-tently with available training tools.This is the first study to report test-retest reliability for the BESTest.

ValidityThe BESTest had the best validity,with higher correlation to all mea-sures of disease severity and self-perceived balance than the BBS andFGA. The highest correlation, though,was between the BBS and the BESTest,signifying that balance is still the pri-mary construct being assessed. TheFGA had moderate overall validity;its highest correlation was with theBBS. Both the FGA and the BESTestare valid measures of balance in in-dividuals with PD.

Ceiling Effect in the BBSAlthough the BBS is a good assess-ment of balance in other popula-tions42 and has served as a functionalbalance and fall risk measure in thepast,28,43,44 it does not challenge bal-ance sufficiently to allow detectionof balance impairments across thefull disease spectrum of PD. The BBSdoes include standing up, turningaround, and bending over, which are3 of the most common ways fallsoccur in people with PD.3,9 How-ever, unlike the situation where fallsoccur, the items allow full attentionto be allocated to these simple tasks,possibly missing those who wouldlose their balance under nontestedcircumstances. It has been shownthat attention allocation can drasti-cally change balance deficits in indi-viduals with PD, whether it is a dual-

task situation or the individualperceives that he or she being ob-served.3,45,46 The participants werefully focused, and many were able tosuccessfully complete the BBS items,although these same tasks are prob-lematic under normal circumstances.Bradykinetic and improperly scaledpostural adjustments also are impli-cated for loss of balance in peoplewith PD,11,13,47,48 which many of thestatic items in the BBS do not requireor require at minimal levels only.Due to these missing components inthe test, the ceiling effect noted inprevious studies10,12 is quite severe.Twenty-five percent (n�5) of thefallers in this study scored within thetop 10% of the BBS, and 4% of fallers(n�1) received a perfect score. TheBBS is unable to identify some indi-viduals with PD who are at risk forfalls, let alone identify the more sub-tle balance deficits that occur in thedisease prior to the occurrence offalls. According to Steffen and Seney,12

the BBS score must change at least5 points to show a true change inbalance. Therefore, 43% of the indi-viduals in our study (those scoring�52/56) would not even be able toshow any balance progress using theBBS. This lack of ability to identifyearly balance impairments in individ-uals with PD may prevent importantearly intervention measures.2,39

Identifying Fallers and NonfallersWe present cutoff scores for makingdistinctions between fallers and non-fallers using 2 methods. The firstmethod maximizes both sensitivityand specificity, minimizing bothfalse-positive and false-negative iden-tifications of fallers. The secondmethod maximizes sensitivity andminimizes LR�. This second methodhas been included to allow compar-ison with prior cutoff scores re-ported in the literature. Both meth-ods maximize sensitivity, as havinghigh sensitivity is important for de-ciding who is at risk for falls. How-ever, there is a trade-off between

sensitivity and specificity, as shownby the large decrease in specificitywhen the second method was used.High sensitivity paired with lowspecificity causes an increase in thefalse-positive rate. While the harmof false negatives is apparent (ie,missing someone who was at riskfor falling), there is perhaps equalharm in false positives, as inappro-priately treating an individual who isnot truly at risk for falling can becostly to society, an inappropriateuse of the patient’s limited financialresources, and a drain on the individ-ual’s (as well as the caregiver’s) timeand energy.

When discriminating who is a faller,the suggested cutoff value of 47/56for the BBS was chosen based onmaximized sensitivity and specific-ity. This cutoff is between the pointschosen in prior studies. A cutoffvalue of 44/56 was suggested byLanders et al28 by maximizing thechange in positive posttest probabil-ity, which allows for a higher false-negative rate. Dibble and Lange22

chose 54/56 by maximizing sensitiv-ity and minimizing LR�, which al-lows for a higher false-positive rate.Applying the same method used byDibble and Lange to the present datawould yield a cutoff of 52/56. Differ-ences in definition of fallers and infall rates, as well as mode of recruit-ment, could contribute to the differ-ences seen between the present re-sults and those of Dibble and Lange.Dibble and Lange22 defined a falleras someone having 2 or more falls ina 12-month period, their study had a51% fall rate, and all participants hadbeen referred for physical therapy.Our study included participants fromthe community who were not ac-tively seeking treatment and, theo-retically, less impaired.

The FGA cutoff value for identifyingfallers was 15/30 when maximizingsensitivity and specificity. No ceilingeffect seen for the test, showing that

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the changes made to the DGI to cre-ate the FGA were effective.14 Thesensitivity and specificity for identi-fying fallers in our study were 0.72and 0.78, respectively.

When maximizing sensitivity andspecificity, the BESTest had the high-est sensitivity of the 3 tests withoutcompromising specificity. Based onthe current study, the cutoff scorefor identifying fallers among individ-uals with PD is 69%. The overall pre-dictive accuracy was highest for theBESTest based on the AUC, althoughonly slightly higher than for the BBSand FGA. The higher AUC indicates ahigher probability that those whoare fallers will have a worse balancescore than those who are not fallers.Eighty-five out of 100 times, theBESTest score of a randomly selectedindividual who is a faller will be lowerthan the score of a randomly se-lected individual who is a nonfaller.

It is important to understand that thepurpose of cutoff scores is to helpidentify those who are at greater riskclinically for falling. However, theyare not to be used as a true dichoto-mous scale. Those near the cutoffscores are at more risk than thosewho are farther away (higherscores). The cutoff values presentedare to be used by clinicians to helpunderstand the scores on these testsand the balance impairment level ofthose who fall normally comparedwith those who do not fall.

The LR can be interpreted as howmany times more likely a faller is toreceive a score below the cutoff thana nonfaller.49 For example, the BEST-est had the highest LR�, with a fallerbeing 3.5 times more likely to score�69% than a nonfaller. The BESTesthad the lowest LR�, with fallers0.21 times more likely to have ascore above 69% than nonfallers. Allposttest probabilities should be com-pared with the pretest probability of31% in this study.

To assess use of these cutoff scoresin a clinical population with higherdisease severity, a sensitivity analysiswas completed, identifying fallers inindividuals with Hoehn and Yahrscale stages 2.5 to 4.0 only (fallerrate�47%). In all 3 tests, the cutoffvalues chosen using both previouslymentioned methods were the sameas or slightly lower than what is pre-sented using all study participantsHoehn and Yahr scale stages 1 to 4,except for the BBS, which suggesteda cutoff value of 55/56 for maximiz-ing sensitivity and minimizing LR�.

Although other literature suggeststhat a combination of tests should beused to assess balance in individualswith PD, the recommendations arehighly variable. Lim et al19 suggestedthe combination of the UPDRS,UPDRS-3, Timed “Up & Go” Test,Functional Reach Test, and timed 10-meter walk for assessing balance inthe home. Dibble et al21 proposedthe use of multiple tests to increasethe posttest probability of accuratelyassessing who was at risk for falling.They used prior reported cutoffvalues of the Functional Reach test,Dynamic Gait Index, BBS, and Timed“Up & Go” Test and then determinedfall risk based on the number of testson which the individual scored belowthe cutoff value. The combination sug-gested by Mak and Pang20 to identifyrecurrent fallers and nonrecurrentfallers includes only the UPDRS andABC scores. Each study agrees that acombination of assessments is neces-sary due to the multifaceted structureof balance, although all the resultingsolutions are different.

The BESTest is the only test, or com-bination of tests, that has differentitems categorized according to thetheoretical control systems of bal-ance. This design might allow theidentification of fallers, as well ashelp determine the main contributorto the underlying balance deficit. Aspecified combination of items, as

presented in the BESTest, would al-low standardization of clinical andresearch evaluations to enable com-parisons to be made, as opposed tohaving each therapist or researcherpick from an assortment of balancetests.

LimitationsOne limitation of the study is the useof a retrospective fall report. How-ever, Bloem et al9 found a similar rateof falling (25%) in a 6-month pro-spective study of falls in individualswith PD. Another limitation is thatthe balance tests were not random-ized. This limitation did not seem toaffect the outcome of the study, asall participants finished the tests,and during the reliability subset, theBESTest was highly reliable, althoughit was administered toward the end oftesting. Participants also were allowedto rest as often as they wanted to pre-vent any fatigue.

For reliability testing, only one rateractually performed the balance tests,while the other raters concurrently ob-served. Although there is a writtenscript for administering the tests, thepossible differences among testers’verbal and nonverbal communicationmay have contributed to increasedvariability in participant performancehad the raters each administered thetests separately. For all testing, the rat-ers were blinded only to fall status.

Summary and ImplicationsFuture studies should focus onwhether the FGA and BESTest arepredictive of falls using the cutoffpoints described here in a prospec-tive manner. The responsiveness ofthese balance tests to assess changein a single individual over time (ie,clinically significant differences inscores) also is important to explorefor better clinical discrimination ofeffectiveness of different balanceinterventions.12,50 A shortened ver-sion of the BESTest that is specific

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for individuals with PD might in-crease its use in the clinical setting.

In summary, the BBS has a ceilingeffect and thus may not adequatelyassess balance in the early stages ofpostural instability in individualswith PD. Both the FGA and the BEST-est are reliable and valid measures ofbalance that can be used throughoutPD Hoehn and Yahr scale stages 1 to4. Both tests can be used to discrim-inate between fallers and nonfallers.The BESTest has the highest sensitiv-ity for identifying who is a faller;however, it takes longer to adminis-ter than the FGA or BBS.

All authors provided concept/idea/researchdesign and data collection. Ms Leddy pro-vided writing, data analysis, and clerical sup-port. Ms Leddy and Dr Earhart providedproject management and fund procure-ment. Dr Crowner and Dr Earhart providedparticipants and consultation (including re-view of manuscript before submission). DrEarhart provided facilities/equipment. Spe-cial thanks go to all of the research partici-pants for their time, as well as to Ryan Dun-can, John Michael Rotello, and Vanessa Heil-Chapdelaine for their help with datacollection.

The study was approved by the Human Re-search Protection Office of Washington Uni-versity School of Medicine.

This research was presented in abstract/poster format at the Missouri Physical Ther-apy Association Spring Conference; April16–18, 2010; St Louis, Missouri; at the Na-tional Predoctoral Clinical Research TrainingProgram Meeting; May 3–4, 2010; St Louis,Missouri; and at the World Parkinson Con-gress; September 28–October 1, 2010; Glas-gow, Scotland.

This publication was directly funded by theDavis Phinney Foundation and grant UL1RR024992 and sub-award TL1 RR024995from the National Center for Research Re-sources (NCRR), a component of the Na-tional Institutes of Health (NIH), and NIHRoadmap for Medical Research. Additionalsupport was provided by the Greater St LouisChapter of the American Parkinson DiseaseAssociation (APDA) and the APDA Center forAdvanced PD Research at Washington Uni-versity. Its contents are solely the responsi-bility of the authors and do not necessarily

represent the official view of the Davis Phin-ney Foundation, NCRR, NIH, or the APDA.

This article was submitted March 31, 2010,and was accepted August 15, 2010.

DOI: 10.2522/ptj.20100113

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doi: 10.2522/ptj.20100113Originally published online November 11, 2010

2011; 91:102-113.PHYS THER. EarhartAbigail L. Leddy, Beth E. Crowner and Gammon M.Disease Who FallSpecificity for Identifying Individuals With ParkinsonSystem Test: Reliability, Validity, Sensitivity, and Functional Gait Assessment and Balance Evaluation

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