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1997; 77:19-27.PHYS THER.Kuchibhatla, Julie Chandler and Carl PieperMargaret Schenkman, Toni M Cutson, MaggieMeasures for Persons With Parkinson's DiseaseReliability of Impairment and Physical Performance

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Reliability of Impairment andPhysical Performance easures forPersons With Parkinson s D isease

Background and Purpose Parkinson s disease (PD) is characterized byrigidity, postural instability, bradykinesia, and tremor, as well as othermusculoskeletal impairments and functional limitations. The purposeof this investigation was to determine the reliability and stability ofmeasures of impairments and physical performance for people in theearly and middle stages of PD. Subjects Thirteen men and 2 women inHoehn and Yahr stages 2 and of PD participated. Their mean age was74.5 years (SD=5.7, range=64-84). Methods Thirteen impairment-level variables and 8 physical performance variables were measured.Measurements were taken on two consecutive days and again a weeklater on the corresponding two consecutive days. Reliability andstability were assessed using analysis of variance and intraclass correla-tion coefficients (ICCs). Results Test-retest reliability (ICCs) of vari-ables ranged from .69 (hamstring muscle length) to .97 (lumbarflexion). Intraclass correlation coefficients were .85 or greater for 10 ofthe variables. Conclusions and Discussion The results suggest that inthe early and middle stages of PD, many of the measures of impairmentand physical performance are relatively stable. [Schenkman M,Cutson T, Kuchibhatla M et al. Reliability of impairment and physicalperformance measures for persons with Parkinson s disease. Phys Ther.1997;77:19-27.]

KeyWords Neuromusculoskeletal disorders, Parkinson s disease; Tests a nd measurements, func tiona l.

Margaret SchenkmanToni M utsonMaggie KuchibhatlaJulie Cha ndlerCarl Pieper

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arkinson's disease (PD) is a disease of olderindividuals affecting 100 to 15 of every100,000 people in t he United States, with aprevalence of about 1% of those over the age of

60 years.' Parkinson's disease results from neurotrans-mitter imbalances associatetl with degeneration of thesuhstantia nigr;~.'. The primary impairments typic;tllyare rigidity, bradykinesia, tremor, and postural instahili-

In addition, people with PD often have stooped,flexed posture, characterized by excessive thoracickyphosis and loss of lumbar lordosis.* Mobiliq of theneck, torso, and extremities is also lost. Furlctionallimitations in bed mobility, transfers, and gait maybecome severely disabling as the disease progresses.Physical therapy for persons in the early stages of PD isdirected at correcting tn~~sciiloskeletaln~pairments ndimproving physical performance. . Reliable and v;tlidrneasl~req f the impairments a nd funr tional limitationsassociated with PD are important for clinical practicean d are a prerequisite to clinical investigations of PD.Various approaches have been reported for rating thesymptoms of people with PD. -lo Recently, a few investi-gators have reported on the reliability or validity of scalesused to rate PD1O.'l r.have compared the performanceof different r a t i ~ ~ g It is evident from suchstudies that the scales often measure different aspects ofPD and that it is not feasible to cornpare patients whohave been rated by different scales.' 1:'Mo5t measures used to quantify impairments or physicalperformance of persons with PD are global measures

that characterize the overall effects of the disease (eg,the Hoehn a nd YahrI4 score used to stage the patient),rely heavily on the patient's self-report (e g, UnifiedParkinson's Disease Rating S ~ a l e , ~orthwestern RatingScale ), or emphasize the direct effects of the disease,including tremor and rigidity.lMost of the scales alsoare ~onstructe do bc used across the full range of stagesof PD. None of the available measures quantify thepatient's muscl~loskeletal impairm ents or provideperformance-based measures of function across a rangeof activities associated with activities of daily living.Reliahlc measurements obtained by phyqical examina-tion may be particularly difficult to obtain for personswith PD because of the fluctuating nature of the disease.Signs and symptoms vary with the time of day, medica-tion schedule, and anxiety level.?This study was designed to examine the reliability ofperformance-based measures of particular relevance tothe functional mobility of persons in the early andmiddle stages of PD in order to establish the utility ofthese measures in research and clinical investigations.The measures investigated were chosen to represent arange of impairments (eg, forcc production, range ofmotion [ROM], spinal config~lra tion lumbar lordosis,thoracic kyphosis]) and of physical performance (eg,balance control, transfers, walking).The purposes of the investigation were 1 to determinewhether there were systematic variations in th e variablesby day or week of testing and (2) to determine thetest-retest reliability of measurements obtained for thevariables ~nvestigated.

M Sch rnkm an. Phl), PT, is Assori;l te Profescnr. ( ;raduate Progranl in Physical Therapy , Senior Fellow, Cen ter for thr S t ~ ~ d yf Aging and Hu manDevelopment, and Co-Director, ( ; l ;~udcD Pe pper O ld er Amer icans In dep rnd enr e ( ;en te r. Duke Universi ty, Durham , NC 27710. Address allc o r r e s p o n d e n c e t o D r S ch e n k m a n ; ~ the ( :en te r fo r the S tudy o l i lg in g an d Hl lman Development , Duke Univers i ty Medica l C en te r , PO Box 3003,Dur hatn , N(: 27710 ITSA) (m.;@geri.drtke.e


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Method than 50,000. Their mean years of education was 16.8(SD=2.4, range=12-21).RatersTwo physical therapists with 7 and 2 years of clinicalexperience, respectively, and two research assistants par-ticipated in this study. They were part of a measurementteam that provided all measures for four interventionstudies of t.he Claude D Pepper Older Americans Inde-pendence Center (OAIC) at the Duke University Centerfor the Study of Aging and Human Development. Themeasurement team performed these measures on aroutine basis and had measured more than 100 subjectsat the time that this study was conducted. Prior to ratingsubjects for the OAIC Measurement Core, all ratersunderwent a training session, including performance ofmeasures and consistent use of the protocols, and acheckout with a physical therapist who was experiencedin the use of these measures and who was a coinvestiga-tor in one of the OAIC studies. The same rater evaluatedthe same participant for each of the four sessionswhenever possible. Because this reliability study was partof a large, ongoing study, this was not always feasible.SubjectsSubjects were included who had been diagnosed by aneurologist as having PD, who were able to ambulateindependently, and who had been on a stable drugregimen for at least 1 month. Subjects were excluded iftheir Folstein Mini Mental State Examinationl%core wasless than 3, if they had been hospitalized within theprevious 3 months, or if they had symptoms of anotherneurological disease (eg, cerebrovascular accident). Thesubjects were recruited from Durham, NC, and thesurrounding areas. The subjects who participated in thisinvestigation were a subset of the participants in a largerrandomized clinical trial examining the effects of exer-cise in persons with PD. All subjects signed an informedconsent statement prior to participation.Thirteen men and 2 women who were independentambulators participated. Characteristics of the partici-pants are shown in Table 1.The mean age of the subjectswas 74.5 years (SD=5.7, range =64-84). Eight partici-pants were in stage 2 of PD, according to Hoehn andYahr's staging for PD,14 and 7 participants were inHoehn and Yahr stage 3. By definition, patients inHoehn artd Yahr stage 2 are independent ambulatorsand have unilateral symptoms and intact balance;patients in, stage 3 are independent ambulators and havemore severe bilateral signs of the disease and impairedbalance. Two of the subjects used assistive devices (caneor walker) some of the time. The other subjects walkedwithout an assistive device. Income and educational levelfor this group were high. Four of the subjects reportedhaving annual incomes of 20,000 to 50,000; theremaining; subjects reported having incomes of greater

Subjects underwent a brief medical examination prior toentering the study. At that time, medication history, thestatus of tremors, rigidity, and Hoehn and Yahr stagingof disease were dete rmined. Subjects were tested on twoconsecutive days and again a week later on the corre-sponding two consecutive days.VariablesThe variables measured in this study included ROM (9variables), spinal configuration (2 variables), muscleforce (2 variables), and physical performance (8 vari-ables). Whenever possible, published protocols withestablished reliability were used. In some instances,when no protocol or reliability information was avail-able, we report the findings of a preliminary reliabilitystudy of a cohort of community-dwelling elderly peoplewho were without specific diseases.17 A few of the mea-sures were included for which no preliminary reliabilitystudy had been carried out and for which the currentreport represents the first reported reliability.ProcedureAll impairment-level variables (eg , ROM, muscle force)and one physical performance variable (the &minutewalk) were measured by a physical therapist. The sametherapist took these measurements for the four testsessions for 12 participants and for 75% of the testsessions for the remaining subjects. All physical perfor-mance variables (except the &minute walk) were mea-sured by a research assistant. The same research assistanttook the measurements for four test sessions for 9participants and for 62% of the test sessions for theremaining 6 subjects. The total battery of measures tookbetween 45 minutes and 1% hours to perform, depend-ing on the participant's functional ability.To minimize the effects of fluctuations of drug levels,subjects were requested to take PD medications at thesame time on each day of testing, and the time of the testsession was held constant. A research assistant called thesubjects prior to each test session to remind them whenthey previously had taken their medications. Duringeach test session, if the variables were measured morethan once, the mean value was the variable used in theanalysis. Because these measures were part of a battery oftests used in an intervention study, decisions were madeto reduce respondent burden. Two trials were per-formed for primary outcomes, and the data were aver-aged. A single trial was performed for other variables.Impairment measures Measures related to the spineincluded spinal configuration, lumbar ROM, and cervi-

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Tahle 1.Characteristics of the SampleNo. of YearsSince Folstein MiniDiagnosis of Hoehn and Mental State Use ofSubject Gender/Age Parkinson s Yahnl4 Antiparkinsonian Examina- Assistive

No. Y) Disease Score Medications tionla Score Device Tremora Rigidityb1 M/80 6 3.0 Sinemeta 2 4 N o +2 M/69 1 2.5 Sinemete 27 No N o3 F/75 11 2.5 Sinemet8 30 Cane N oAmantadine4 M/ 84 8 2.5 Sinemetm 26 N o N o +Eldepryl85 F/80 2 0 2.5 Eldepryl 29 N o6 M/ 69 4 2.0 Sinemeta 30 N o N oEldeprylm7 M/ 74 2 3.0 Sinemetm 29 N o ++ +8 M/6 4 1 3 O Sinemete 28 No N oEldepryl9 M/7 9 5 3.0 Sinemet@ 30 N o +

10 M/6 9 18 3.0 Sinemeta 3 0 N oEldeprylaParlodel@1 1 M/7 2 3 2.5 Sinemet@ 28 N o N oEldepryle12 M/ 78 2 2.5 Sinemeta 30 N o +Eldepryl13 M/ 79 7 3.0 Sinemeta 28 Cane N oEldeprylo Walker14 M /7 9 2 2.5 Sinemeta 29 Cane N oEldepryla15 M/ 69 3 3.0 Sinemeta 2 8 No ++ +Eldepryla

+=mild; ++=moderate: prewnt a n r l visible, only occasionally bothersollie; +++ =se ver e: constant and very obvious.%=mi ld: only apparent with rrinli,rc r~nent;++=moderate: present butjoint can be fully extended with paqsive range of motion; +++=severe: limits availablepassive range of ni


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subjects were instructed to side bend as far as possible.The degrees of maximum right and left side bendingwere read from the inclinometer. Test-retest reliabilityhas been reported for all measures for a sample ofelderly subjects with osteoarthritis (ICCs= .72-.94) .I9Th e mobility of the cervical spine was measured with thesubjects in a sitting position using the Cervical Range ofMotion (CROMTM) n ~ t ru m e n t . ~~ ~) , ~ ~ith the CROMTMinstrument on the head and the magnetic yoke on thechest, each subject's resting position was recorded. Thesubject was then instructed to move as far as possible intoeach plane of motion (flexion, extension, side bending,and rotation). The maximum degrees of motion foreach trial were read from the appropria te inclinometer.Data from two trials were averaged for each motion.Test-retest and interrater reliability have been estab-lished for- measurements of all planes of motion forasymptomatic individuals (ICCs=.76 or ab o ~ e ) . ~ O . ~ ~Standard goniometric techniques2' were used to mea-sure extremity ROM (ie, shoulder flexion and ankledorsiflexion). Data were recorded from a single trial.Hamstring muscle length was determined with the sub-ject positioned supine. The hip was flexed to 90 degrees,and then the knee was extended to the point of resis-tance. The angle between the tibia and the femur wasrecorded as a measure of hamstring muscle length.23Extremity muscle force was measured using a hand-helddynamonleter and a modification of published meth-0ds.2~.'511 Chatillon hand-held dynamometerx was usedto obtain isometric measurements of peak force. Ankle

Functional axial rotation26 is a measure of combinedspinal motions that we believe relate to functional abil-ities. The validity of the FAR measure is indicated by itscorrelation with physical performance measures thatincorporate motion of the neck and back (canonicalcorrelation coefficient 60, P .005) z7 Functionalaxial rotation was assessed with the subject seatedand the pelvis stabilized by Velcro@ trapsa hoop withsymbols (numbers and letters) in 5-degree incrementswas suspended at eye level by two tripods, one in front ofthe subject and the other behind the subject. Theheadpiece of the CROMTMnstrument was placed on thesubject's head. The forward head arm of the unit wasused as a pointer oriented toward the hoop . Th e subjectwas instructed to turn as far as possible to the right andthen to the left and to report the farthest symbol thatcould be seen. The symbol with which the pointeraligned was recorded as FAR. practice trial and two testtrials were conducted, and the data were averaged.Excellent interrater and test-retest reliability have beenreported (ICCs= .90 or above) .26Functional reach,28 a measure of balance control, wasmeasured with the subject in a standing position.yardstick was positioned on the wall at the height of theacromion. The subject's dominant arm was held in 90degrees of shoulder flexion. Th e subject was instructedto reach as far forward as possible without taking a step,and the distance reached was recorded. Two practicetrials and three test trials were performed. Data from thethree test trials were averaged. Excellent interrater reli-ability has been reported for a sample of elderly individ-uals (ICCs= .90 or above) .3s

dorsiflexion force was measured with the subject in asitting position (hip in abou t 90 of flexion, knee in 45 digital stopwatch was used to time the subject duringof flexiom, and ankle in 30 of plantar flexion). The movement from a supine position on a low treatmentdynamometer was applied perpendicular to the metatar- table to a standing position. The subject was instructedsal heads. Hip abduction was measured with the subject to move at his or her normal pace. The subject was thenpositioned supine and with the leg in a neutral position. given the same instructions and requested to return to aThe thigh-segment length from the greater trochanter supine position. One practice trial and two test trialswere conducted for each variable, and the data wereto the position of the dynamometer was measured and averaged.used to calculate the actual force produced. practicetrial was conducted, followed by two test trials. The data The 360-degree measures the number of steps andwere averaged. Prior to initiating this study, interrater the time required to turn around in place in a standingreliability was established for asymptomatic elderly sub- position. A digital stopwatch was used to time the taskjects for ankle doniflexion (ICCZ.93, right side; and the number of steps was recorded. Each subjectICC=.95, left side) and hip abduction (ICC=.89, right completed two test uials to the right side, and the dataand left sides) I7 were averaged. Similarly, each subject completed two

trials to the left side, and the data were averaged. Time'~YS' ' performance me'SureS. Measures physical (in seconds) and number of steps were recorded.performance included a series of tasks that requiredmobility of the spine, such as twisting, looking behind For the &minute walk, the subject was requested to walk(functional axial rotation [FAR]), and walking. at a comfortable pace for 6 minutes.29 Distance was

recorded for a single trial.

:Jo hn Chat~l lon Sons Inc PO Box 35668 Greensboro NC 27425-5668. SVelcro USA Inc 406 Brown Ave PO Box 5218 Manchester N 03108.

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able2Analysis-of-Variance Table for Parkinson s Disease Reliability Experimento

df SS M S M S IBebeen subjectsWithin subiectsTotal

N-(15-1)Nk-N(15xk-15)Nk-

iN 16 ks

k=total number of measuren~rntsper subject, N=number of subjects, xi=mean of the k readings for subject i, x=mean ot all readings, =variance of the kreadings for subject i, S2=variance of all readings across all subjects, cr2=expectrd within-person (error) variance, :=expect ed hetweenperso n (true) variance,RMS=between mean squares, WMS=within mean squares, EMS=expecttd mean

For the 10-m walk, a 10-m distance was marked on thefloor.30 The subject was instructed to walk at a comfort-able pace. The subject began this test 5 m before thestarting line and completed the test about 5 m after thefinish line. Time was recorded from the time when thesubject crossed the starting line to the time when he orshe crossed the finish line. Each subject completed twotest trials, and the data were averaged.Data AnalysisVariation by day or week of testing. Each variable wasmeasured during four different test sessions (days 1, 2, 8,an d 9) . We used a repeated-measures analysis of variance(ANOVA), with the repea ted observations nested withinsubjects, to determine whether there were systematicfluctuations by day or week of testing. For each variable,data were included in the ANOVA and the reliabilitydeterminations only if data existed for all four testsessions (ie, listwise deletion was used in the analysis).This analysis allowed us to determine whether the mea-surements obtained fluctuated in any systematic way (eg,due to learning effect over 4 days of testing).Test retest reliability. Intraclass correlat ion coefficientswere used to determine test-retest reliability. Becausethere were no systematic variations by day of testing forthe variables investigated (see Results sect ion) , weobtained the necessary variance estimates for reliabilityassessment by assuming that the four sessions werereplicates. A repeated-measures design with the fourreplicate measures was used (see Tab. 2 for the ANOVAtable used in these es timates). Thus, using the assump-tion of classical test theory,31 we assumed tha t only twosources of variation were possible: subject (intersubject)and variation within the subject (intrasubject).ResultsThere was a wide range in the measurements for theimpairment variables for this sample (Tab. 3). Forexample, measurements ranged from 25 to 77 degreesfor cervical extension, from 122 to 174 degrees forshoulder flexion, and from 4 to 38 degrees for lumbarlordosis. Similarly, measurements for the physical per-

squares

formance variables varied greatly across the sample.Measurements ranged from 14.7 to 43.7 cm for func-tional reach, from 209.7 to 634.0 m for the 6-minutewalk, and from 2.9 to 14.5 seconds for the time to movefrom a sup ine position to a standing position.We first determined whether there were differences inthe variables obta ined across the d ifferent days or weeksof testing (Tab. 3). Th e repeated-measures ANOVA(days nested within subjects) revealed probability valuesof greater than .05 for all of the variables except forvariables of the 360-degree turn in a standing position(time and number of steps). That is, for the most part,there were no effects of day or week of testing. Withmultiple iUVOVAs, there is an increased probability offinding a significant result.31 With a Bonferroni correc-tion for multiple testing, the observed differences werenot significant. Thus, the repeated-measures ANOVArevealed n o effect of time, and the four da ta points couldbe used in the reliability estimates without control fordays as an additional source of variation for eachvariable.The estimate of reliability and the lower confidenceinterval for each of the measures are reported in Table4. Test-retest reliability (ICCs) for impairment variablesranged from a low of .69 (for hamstring muscle length)to a high of .97 for lumbar flexion (Tab. 4) . Test-retestreliability was .85 or bette r for 7 of the 13 impairmen tvariables and .90 or better for 4 of the variables. Ingeneral, variables related to the lumbar region had thehighest reliability, followed by variables of spinal config-uration and muscle force . Lower-extremity ROM had thelowest reliability.Test-retest reliability (ICCs) for physical performancevariables ranged from .77 for the steps in the 360-degreeturn and for the supine-to-stand task to .95 for the6-minute walk (Tab. 4) . The ICCs were greater than .85for 3 of the 8 variables and greater than .90 for 1variable. The lower confidence intervals were above 0.07for 2 of the variables measured.

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Table 3Mea surem er~ts bta ined on Four Differe nt Days, Including Means for Each Session, Un ivariate Statistics for the Combined Means, and Results ofan Analysis of VarianceNo of SampleaVariables Subjects Day 1 Day 2 Day 8 Day 9 X SD Range P

lmpairmer~t ariablesAxial configuration andmotion O)Thorc~cic yphosis 15 44. 2 44.2 44 .5 43.9 4 4.4 11 O 22 -6 7 .38

Lumbar lordosis 15 23.5 20 .9 21.4 22. 2 22.4 8.0 4-3 8 .07CervicalFlexion

ExtensionRotation

LumbarFlexionExtension 15 78.9 79.0 76.7 76.7 77.7 9.8 58-10 0 .30

Extremity range of motion 1 )Shoulder flexion 15 151.0 150.7 150.6 152.3 150.4 12.2 122-1 74 .85Hip flexion contracture 15 5.6 5.3 5.2 5.1 5.3 4.1 2-1 4 .99Ankle dorsiflexion 15 5.8 5.6 5.4 5.2 5.4 4.8 6-1 4 .98Hamstring muscle length 13 42 .7 42.8 43.1 43. 4 42. 9 6.9 27-55 .9 7

Force nneasures (pounds offorce)Hip abduction 15 39.1 38.0 40.9 39.2 38. 3 15.7 5.7-72 .78Ankle dorsiflexion 15 15.5 15.3 15.8 15.8 14.9 5.3 1.2-25.8 .95

Physical performance variablesFunctional axial rotation ( ) 15 92.8 94.5 90.5 90.7 91.0 16.0 60-1 25 .5 1Functional reach (cm) 14 32.3 33.3 34.3 33. 0 32 .5 6.6 14.7-4 3.7 .38360degree turn (s) 14 5.5 5.6 6.2 5.7 6.0 2.5 3.8-15.9 .02360-degree urn (steps) 14 9.0 9.2 10.8 9.4 9.5 2.9 5.5-1 8.5 .01Supine to stand (s) 14 5.4 5.9 5.7 5.3 5.6 2.2 2.9-14.5 .65Stand to supine (s) 14 5.2 5.3 5.6 5.2 5.3 1.6 3.2-9.0 .426-minute walk (m) 12 477.6 455.1 468.2 478.8 461.5 94.8 209.7-634 .1910m walk (s) 14 8.5 8.4 8.5 8.1 8.8 2.7 5.8-17.2 .31

~Sample mc:an and standard deviation refer to the mean and standard deviation for all subjects and all test sessions; sample range refers to the range for all

uhjrcts and ll test sessions

DiscussionThere is a need for measures that clinicians andresearchers can choose when characterizing capabilitiesan d limitations of patients who have PD. Such measuresare required in order to monitor decline du e to thedegenerative nature of the disease), to assess improve-ment with intervention, and to investigate the benefits ofinterventions. This investigation provides the first rep or tof reliability of measurements of impairment and phys-ical performance obtained by clinical examination forpersons with mild to moderate PD. Although the samplesize was small, the results provide information that canguide the choices that clinicians and researchers makeregarding measurement.

Prior to establishing test-retest reliability, it was necessaryto dete rmine the effects of day or week of testing on thevariables. There were few systematic variations by day orweek of testing for t he impairment and physical perfor-mance measurements obtained on four different daysspanning a week. Subjects were always tested at t he sametime of day and at the same time relative to takingantiparkinsonian medications , which may have contrih-uted to the lack of effects for day or week of testing.Next, we determined the test-retest reliability of themeasurements obtained for the variables. ReliabilityICCs) was a t least .69 an d is comparab le to the reliabil-

ity reported for these measures for subjects without

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Table 4lntraclass Correlation Co efficients ICCs) for Reliability of Impairmentand Physical Performance MeasuresLower

No of ConfidenceMeasure Subjects ICC lnhrvalAxial configuration

Kyphosis 15 93 0 88Lordosis 15 87 0 78Axial rangesLumbarFlexion 15 97 0 94Extension 15 94 0 88CervicalFlexion 15 78 0 64Extension 15 87 0 78Rotation 15 84 0 72Extremity range sUpper extremityShoulder flexion 15 80 0 67Lower extremityHip flexion 15 72 0 56Hams tring muscle

length 13 69 0 49Ankle dorsifkxion 15 80 0 . 6 6Extremity forceAnkle dorsiflexion 15 91 0 84Hip abduction 15 88 0 78Physicol performanceFunctional axia l rotation 15 89 0 81Functional reach 14 84 0 71Supine to stand 14 77 0 61Stand to supine 14 80 0 45360-degree turnSteps 14 77 0 61Time 14 80 0 .666-minute walk 12 95 0 901 0 m walk 14 87 0 77

PD.17-21,2 ,'7 Because the sample size was small, we alsocalculated the lower confidence intervals, which likewisesuggested that the reliability achieved was acceptable.There are several sources of variation contributing to theestimate of test-retest reliability: rater, within andbetween subjects, and instrument. Test-retest reliabilityfor axial ROMs tended to be higher than the test-retestreliability for extremity ROM and physical performance.There is considerable room for subject variability inphysical performance of tasks because of the many waysby which the tasks can be carried out. In addition, theend point of many physical performance tasks (eg,supine to standing) may be more difficult to pinpointthan the end points of measures of ROM. Variability insubject performance and rater performance might con-tribute to the generally lower test-retest reliability of thephysical performance measures compared with the mea-sures of axial motion. Whichever factors contribute,these measures generally have acceptable reliability,using Domholdt's criteria.32

Reliability estimates can be enhanced when scores frommultiple trials are averaged to produce a single score(indicator) per subject. The improvement in reliabilityhas been shown to be related to the number of trialsfrom which data are obtained using the Spearman-Brown prophesy f~rmula.~'When working with subjects who have symptoms that a reknown to fluctuate, or when using measures for which itis difficult to def ine precise end points, reliability may beimproved by measuring the subject on two different daysand averaging the data. Using the Spearman-Brownprophesy formula, we would expect a test-retest reli-ability (ICCs) of 3 7 or above for all of the physicalperformance variables measured in this study if data aretaken on 2 days and averaged.Although generalizability is somewhat limited by thesmall sample size of this study, the results indicate thatacceptable reliability can be achieved for measures oflimitations and physical performance for people in theearly and middle stages of PD when therapists aretrained to take these measurements. The measures weinvestigated can be used with confidence by clinicians orresearchers when working with these patients. In thiscontext, it is important to recognize that the ratersunderwent a training session prior to participation in thestudy. The complete battery of measures may be morethan is required in some clinical situations. The clinicianshould choose those measures that are appropriate forhis or her patient, given the patient's underlying impair-ments and the goals of intervention. Investigations cur-rently are in progress to determine which impairment-level variables correla te with aspects of physicalperformance and function. In addition, we are investi-gating the sensitivity to change of this battery ofmeasures.We studied people who were in the early and middlestages of PD who had relatively stable symptoms, andwho were on a stable drug regimen in order to maximizethe chance of establishing high reliability in this initialinvestigation. Even with rather rigorous inclusion andexclusion criteria, there was a wide range of impairmentand performance measures that contributed to the suc-cess in achieving high reliability. Measures investigatedin this study were chosen because of their importancefor persons in the early and middle stages of PD.Investigations are needed to determine th e reliability ofappropriate measures of impairment and physical per-formance for patients who are not in a stable period withrespect to symptoms of their disease and for patientswho are in the later stages of PD. The reliability of thesemeasurements obtained with larger numbers of thera-pists in clinical practice also needs to be determined.

26 Schenkman et al Physical Therap y. Volume 77 Number 1 January 1997by guest on November 15, 2013http://ptjournal.apta.org/Downloaded from


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ConclusionThe measures tested in our study were chosen to reflectthe physical status of persons with PD. Our resultsprovide additional measures that can be used, in combi-nation with existing self-report measures, for investigat-ing relationships among physical impairments, physicalperformance, and overall functional ability of thesepatients.AcknowledgmentsU'e gratefully acknowledge the following members of theOAIC Measurement Core who collected data for thisstudy: Jama Purser, PT, Sarah Robeson, PT, SuzannHarris, anti Thomas Beischer. We also thank the partic-ipants, who graciously underwent repeated test sessions.References1 Tanner CM.. Epidemiology of Parkinson's disease. ~VeurolClin. 1992;10:317-329.2 JankovicJ. ]Parkinson's disease: recent advances in therapy. So.uth hfedJ 1988;81:1021-1027.

Stary M Jankovic J. Clinical and neurobiological aspects of Parkin-son's disease. In: Huber SJ, Cummings JL, eds. Parkinson s Disease:Neurobehavzoral Aspects. New York, NY Oxford University Press Inc;1992:lO-13.4 Sc he nk ma ~~ . Physical thcrapy intervention for the ambulatorypatient. In: Turnbull G, ed. Physic(11 Therapy Managrrnent o/ Pa rk in so ~~ sDiseu~r.New York, NY Churchill Livingstone lnc; 1992:137-192.5 Cutson TMi, Laub KC, Schenkman M. Pharmacological and nonphar-macological interventions in the treatment of Parkinson's disease. PhysThm. l995;75:363-373.6 Webster DA. Critical analysis of the disability in Parkinson's disease.M o d m T ~ e a t m m t. 968;5:257-282.7 Feldman ICG, Lannon MC. Parkinson's disease and related distur-bances. In: Feldman RG, ed. Neurology: The Physician s Guide. New York,NY: Thieme Medical Publishers Inc; 1984:147-162.8 Fahn S, Elton RL UPDRS Committee. Unified Parkinson's diseaserating scale. In: Fahn S, Marsden CD, Calne DB. Goldstein M, eds.Recent Dmrk~pmenls n Parkinson s Disease, Volume 2. Florham Park, NJ:MacMillan Health Care Information; 1987:153-164.9 Canter GJ, de la Torre R, Mier hl. A method for evaluating disabilityirc patients with Parkinson's disease.JNuruhlenl Dir. 1961;188:14.3-147.1 Henderson L Kennard C, Crawford TJ, et al. Scales for ratingmotor impairment in Parkinson's disease: studies of reliability arrdconvergent validity.J Neural Neurosurg Psychiatq. I991;54:18-24.11 Ginanneschi A, Degl'Innocenti F, Magnolti S, et al. Evaluation ofParkinson's disease: rrliabil~ty f three rating scales. Neuroqbidmzology.1988;7:38-'$1.12 Dlamonc-l SG, Markham CH. Evaluating the evaluations: or how toweigh the ;tales of parkinsonian disability. ,Ve~~rology.983;33:1098-1099.

14 Hoehn MM, Yahr MD. Parkinsonism: onset, progression and mor-tality. Neurolog). 1(967;17:427.15 Fahn S, Toolosa D Marin D. Clinical rating scale for tremor. In:

Jankovic J, Toolosa D eds. P a r k ~ n s o ~ lDisease and Mouernrr~tDtsurcters.Baltimore, Md: Urban and Schwarzenberg; 1988:225.16 Folstein MF, Folstein SE, McHugh PR. "Mini-ncental state": apractical method for grading the cognitive state of patients for theclinician. JPsychiatr Res. 1975;12:189-198.17 Purser JL, Duncan PW, Gold DT, e t al. Reliability of physicalperformance measures. L;nDntologzst. 1994;34:208.18 Ohlen G, Spangefort E Tingvall C. Measurement of sp i ~ ~ a lagittalconfiguration and mobility with Debrunner's kyphometer. Spine. 1989;14:580-583.19 Weiner DK, Distrll B Studenski SA, et al. Does rad iographicosteoarthritis correlate with flexibility of the lumbar spine?JAtn GenatrSoc. 1994;42:257-263.2 Rheault W. Albright B. Byers C, et al. Inter-tester reliability of thecervical range of motion device.J Orthop Sports PIiy.\ Thm. 1992;15:117-150.21 Capuano-Pucci D Rheault W Aukai J, et al. Intra-tester and inter-tester reliability of the ce~vica l ange of 111otiondevice. Arch Phys MedRehabil. 1991;72:338-340.22 Norkirc CC, White DJ. Measurement ofloznt Rongr o jMulion. A G t t zd ~to Goniometq. Philadelphia, Pa: FA Davis Co; 1985.23 Gajdosik RL Giuliani CA Bohannon RW. Passive compliar~ce ndlength of hamstring muscles of healthy men and women. Clin Bionruch.1990;5:23-39.24 Will ian~s %W. Hand-held dynalnometry for measuring musclestrength.Journal of Human Muscle Pcrfoolmc~ncr.199 l:35-50.25 van der Ploeg RJO, Oosterhuis HJGH, Reuveka~~~p. Me;isuringmuscle strength. J ~Veurol. 984;231 200-203.26 Schenkman M, Hughes MA Bowden MG, Studenski SA. A clinicaltool for measuring f~cnctional xial rotation. Phys Thn. 1995;75:151-156.27 Schenkn~anM, Shipp KM ChandlerJ, ct al. Relationships betweenniobility of axial structures and physical pcrt'ormar~ce.Phys Ther.1996;76:276-285.28 Duncan PW, Weiner DK, Chandle r J, Studenski SA. Functiollalreach: a new clinical measure of balance. J Gerontol. 1990;45:M192-M197.29 Guyatt GH, Sullivan MJ, Thompson PJ. Th e 61ni1lute walk: a newmeasure of exercise capacity in patients with chron ic heart h ilu re. C r ~ nMed A~so cJ . 985;32:919-923.3 Weiner DK Bongiorni DR, Studendki SA, et al. Docs tunctionalreach improve with rehabilitation? Arch Phys Mtri Kehabil. 1993;74:796-800.31 FleissJ. The Design ond Anulysu of Cbnzcul Expenm mts. Neb York, NYJoh n Wiley Sons Inc; 1986.3 Domholdt E. I hysrcal 7 htva py Kesercrch: Plzn czpl es nd Atrf~l~rtllzonr.Philadelphia. Pa: WB Saunders Co; 1993:275.

13 Martine-Martin P, Brmego-Parega F. Rating scales in Parkinson'sdisease. In: Jankovic J, Toolosa D eds. Parkinson isease and MouementDisordns. Baltimorc. Md: Urban and Schwarzenberg; 1988:235.

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1997; 77:19-27.PHYS THER.Kuchibhatla, Julie Chandler and Carl PieperMargaret Schenkman, Toni M Cutson, MaggieMeasures for Persons With Parkinson's DiseaseReliability of Impairment and Physical Performance

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