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2000; 80:168-178.PHYS THER.Shu-Fang HsiaoSuh-Fang Jeng, Kuo-Inn Tsou Yau, Li-Chiou Chen andWhen Used on Preterm Infants in TaiwanAlberta Infant Motor Scale: Reliability and Validity

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Alberta Infant Motor Scale: Reliabilityand Validity When Used on Preterm

Infants in Taiwan

Background and Purpose. The goal of this study was to examine thereliability and validity of measurements obtained with the Alberta

Infant Motor Scale (AIMS) for evaluation of preterm infants in Taiwan.

Subjects. Two independent groups of preterm infants were used to

investigate the reliability (n45) and validity (n41) for the AIMS.Methods. In the reliability study, the AIMS was administered to theinfants by a physical therapist, and infant performance was videotaped.

The performance was then rescored by the same therapist and by 2

other therapists to examine the intrarater and interrater reliability. In

the validity study, the AIMS and the Bayley Motor Scale were admin-

istered to the infants at 6 and 12 months of age to examine criterion-

related validity. Results. Intraclass correlation coefficients (ICCs) forintrarater and interrater reliability of measurements obtained with the

AIMS were high (ICC.97.99). The AIMS scores correlated with the

Bayley Motor Scale scores at 6 and 12 months (r

.78 and .90),although the AIMS scores at 6 months were only moderately predictive

of the motor function at 12 months (r.56). Conclusion and Discus-sion. The results suggest that measurements obtained with the AIMShave acceptable reliability and concurrent validity but limited predic-

tive value for evaluating preterm Taiwanese infants. [Jeng SF, Yau KIT,

Chen LC, Hsiao SF. Alberta Infant Motor Scale: reliability and validity

when used on preterm infants in Taiwan. Phys Ther. 2000;80:168178.]

Key Words: Infant motor test, Motor development, Prematurity, Reliability, Validity.

168 Physical Therapy . Volume 80 . Number 2 . February 2000

Resea

rch

Report

Suh-Fang Jeng

Kuo-Inn Tsou Yau

Li-Chiou Chen

Shu-Fang Hsiao

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Infants born prematurely have a higher risk fordevelopmental delays than full-term infants do,with motor delays accounting for the largest pro-portion of these problems.13 Recent approaches to

identifying and treating preterm infants with motordisorders have emphasized assessment and interventionwithin the first year of life.46 Physical therapists areoften the primary evaluators and care providers in theearly identification and treatment of these children andare usually responsible for selecting an infant motorassessment that is clinically practical and psychometri-cally sound.

Physical therapists often relied on testing reflexes andmotor milestones to evaluate infants with motor delaysin the 1970s and 1980s.712 These assessments were basedon the concept that the behavior repertoire of an infant

evolves from a reflexive state to a voluntary state in asequential manner as the nervous system matures.13

Although assessment of reflexes and motor milestones

may provide useful information about the neurologicalintegrity of an infant, increasing evidence indicates thatthe neural maturation explanation alone does notaccount for the complex features of motor develop-ment.14,15 Rather, motor behaviors may emerge as afunction of the cooperation of many contributing sub-systems of the child in a task-specific context.1517 Thisnotion, often referred to as dynamical systems, sug-gests that assessment of infant motor behaviors shouldbe based on multiple factors (eg, neural maturation,muscle force, biomechanical leverages, emotional state,cognitive awareness, constraints of the task and physicalenvironment) that influence motor outcome.1821

Another limitation of the traditional focus on acquisi-tion of motor milestones is the lack of sensitivity inidentifying children with subtle movement prob-

lems.22,23 Several studies showing no benefits due toearly neurodevelopmental therapy in premature infantsused standard age-defined skill development levels.4,24

SF Jeng, PT, ScD, is Associate Professor, School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, No.

7 Chun-Shan S Rd, Taipei, Taiwan ([email protected]). Address all correspondence to Dr Jeng.

KIT Yau, MD, is Professor, Department of Pediatrics, College of Medicine, National Taiwan University.

LC Chen, PT, MS, is Teaching Assistant, School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University.

SF Hsiao, PT, is a graduate student, School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University.

Concept/research design, writing, and data analysis were provided by Suh-Fang Jeng; data collection, by Li-Chiou Chen and Shu-Fang Hsiao; and

project management and fund procurement, by Suh-Fang Jeng and Kuo-Inn Tsou Yau. Subjects were provided by Kuo-Inn Tsou Yau, and

consultation (including review of manuscript before submission) was provided by Kuo-Inn Tsou Yau and Li-Chiou Chen. Linda Fetters, PT, PhD,

provided guidance during the early stage of this study, and Ru-Jeng Teng, MD, also provided consultation. Ru-Jeng Teng, MD, Ae-Wen Huang,

PT, Chun-Hua Wang, PT, Cheng-Chi Tsao, PT, Yi-Lin Chang, Chia-San Wu, and Shiu-Ying Yu assisted in data collection and analysis. The authors

acknowledge the infants and their parents for their participation in this experiment

This study was approved by the Institutional Review Committee of the College of Medicine, National Taiwan University.

This work was supported by a grant from the National Health Research Institute (NHRI DOH 87-HR-619) of the Department of Health and by

the Premature Baby Foundation of the Republic of China on Taiwan.

This article was submitted March 22, 1999, and was accepted September 29, 1999.

Physical Therapy . Volume 80 . Number 2 . February 2000 Jeng et al . 169

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The findings of those examinations indicated that thechildren did not exhibit acquisition of motor skills eventhough they may have shown clinical improvement inpattern and quality of movement. The scope of an infantmotor test, therefore, should be broadened to includequality components (eg, ability to shift weight, postureassumed in the motor task, control of antigravity muscles)

if the accuracy of early identification is to be improved.

The Alberta Infant Motor Scale (AIMS) incorporates theneuromaturational concept and the dynamical systemstheory and is used to measure gross motor maturation ofinfants from birth through the age of independentwalking.25,26 In the AIMS, the impact of neurologicalcomponents on motor development is reflected by asequence of motor skills, which are used as the basis ofassessment.26 The scale follows the principles of dynam-ical systems because motor skills are tested by observinginfants as they move into and out of 4 positions: prone,supine, sitting, and standing (Figure). In theory, thisassessment should allow therapists to see the interplay ofthe childs neuromotor system within the specific physi-cal contexts (eg, gravitational effect) of the motor task.

The items of the AIMS focus on variables such as weightbearing, postural alignment, and antigravity movementthat contribute to motor skills.26 This focus is exempli-fied by the description of the item Supported Standing(3) in Table 1. According to the scoring criteria, theinfant needs to bear weight on his or her feet andmaintain the head in midline, with the hips abductedand laterally (externally) rotated and in line with shoul-

ders. This positioning assumes there is active control ofthe trunk and variable movements of the legs in order toget a passing score for this item. The scoring systementails a dichotomous choice for each test item, scoredas observed or not observed. Using criteria such asthose in the example, the AIMS provides informationthat may assist therapists in identifying the missingcomponents of motor tasks and formulating interven-tion strategies.

The AIMS has been investigated for its practicality andthe reliability and validity of its scores on infants in

Canada.2528

Because the testing procedures are admin-istered by observation only and can be completed within20 minutes, the AIMS is feasible for clinical use. Stan-dardization of the scale was established on 2,202 sex- andage-stratified full-term infants who were randomly sam-pled from all infants in Alberta, Canada.26 The norma-tive data from this study provide the basis for determin-ing whether the motor performance of normallydeveloping infants differs from that of infants withmotor dysfunction. Furthermore, the AIMS has highdegrees of test-retest, intrarater, and interrater reliabilitywhen it is administered on normally developing full-term

infants (reliability greater than .85).26 The correlationsbetween the AIMS and the established infant motor tests(ie, Bayley Motor Scale and Peabody Gross Motor Scale)are also high when these tests are concurrently appliedon infants at risk for motor delays (Pearson product-moment correlation coefficients [r] greater than .80).26

The prognostic value of the instrument in predicting the

18-month motor outcome of infants with very low birthweights (ie, 1,501 g), however, ranges from moderateto high: the sensitivity was 58% to 64%, the specificitywas 83% to 95%, and the positive predictive value was49% to 79%.27 Sensitivity was defined as the proportionof children diagnosed as having abnormal motor devel-opment during childhood who were also classified ashaving delayed motor development during infancy. Spec-ificity was defined as the proportion of children diag-nosed as having normal motor development duringchildhood who were also identified as having normalmotor development during infancy. Positive predictivevaluewas defined as the proportion of children classifiedas having delayed motor development during infancywho continued to have delayed motor development asthey aged.

The theoretical basis, clinical feasibility, and, in ouropinion, some acceptable psychometric test features ofthe AIMS have made it a valuable tool for the evaluationof high-risk infants in Canada. Before the AIMS can beapplied more broadly, however, we believe a cross-cultural evaluation is warranted. Nugent et al29 haveillustrated that the psychometric properties of a devel-opmental test might be influenced by some culture-

specific elements. The AIMS test items are designed toevaluate an infants movement in prone, supine, sitting,and standing positions. Previous studies3033 have shownthat, unlike infants in North America, infants in Asia andEurope are predominantly placed in a supine positionfor sleeping, which has led to later attainment of whatare considered early motor milestones, such as rollingover and sitting up. How such cultural differences mightaffect the administration of the AIMS has not beeninvestigated. The AIMS incorporates a dynamical andqualitative perspective in the evaluation of infant move-ment, a framework that was recently formulated and is

considerably new to therapists.21,34,35

Application of thescale to different populations, in our view, is essential toverify the AIMS designers contention that therapistswith sufficient background in infant motor develop-ment, experience in infant observation, and understand-ing of the criteria for test items can make competent andaccurate use of the AIMS.36,37

Estimates of reliability and validity for the AIMS havebeen made for use with Canadian subjects, but whetherthese estimates suggest that the AIMS is appropriate forinfants of different social and ethnic backgrounds needs

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to be determined. The purpose of this study, therefore,was to investigate the reliability and criterion-relatedvalidity for the AIMS when used by physical therapists onpreterm infants in Taiwan. The reliability studies exam-ined intrarater and interrater reliability. The criterion-related validity studies were designed to examinewhether the outcome of the AIMS could be used as asubstitute for established tests (concurrent validity) and

to predict subsequent developmental outcome (predic-tive validity).

Method

SubjectsOur subjects were 86 preterm infants who were followedat the outpatient clinic of the Pediatric Department at

Figure.Administration of the Alberta Infant Motor Scale on a 6-month-old premature infant in 4 gravitational planes: (A) prone, (B) supine, (C) sitting, and(D) standing.




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National Taiwan University Hospital, Taipei, from April1995 through February 1996. All infants were consideredat high risk for developmental delays because of prema-

turity or the presence of one or more of the followingconditions: birth weight less than 1,501 g, 1- or 5-minuteApgar score lower than 7, intrauterine growth retardation,chronic lung disease, and intraventricular hemorrhage.Intrauterine growth retardation was defined as having a birthweight below the 10th percentile of the intrauterine growthcurve of Taiwanese infants.38 The presence of chronic lungdisease was indicated if the child had continuous oxygentherapy at 28 days of age.39 The severity of intraventricularhemorrhage was graded according to the method of Papileet al.40 Informed parental consent was obtained for allinfants prior to participation in the study.

The infants were subdivided into 2 samples, one to studythe reliability of AIMS scores (n45) and one to studythe validity of AIMS scores (n41). Table 2 illustratesthe neonatal characteristics of each sample. In thereliability study, infants were evenly clustered into 3 agelevels (ie, corrected ages of 03 months, 47 months,and 8 months or older) to ensure a fairly equal repre-sentation of different levels of motor performance frombirth to age 18 months. The AIMS was administered toeach infant once to investigate the reliability of themeasurements obtained. All infants enrolled in thevalidity study had participated in one of our longitudinal

follow-up research projects for infants with very low birthweights. The infants were evaluated with the AIMS andthe Bayley Scales of Infant Development, 2nd edition,

(BSID-II) at corrected ages of 6 and 12 months toinvestigate criterion-related validity. The Motor Scale ofthe BSID-II was used as the standard measure.12

Instrument and ProceduresThe AIMS consists of 58 items that are organized into 4subscales: prone (21 items), supine (9 items), sitting (12items), and standing (16 items).26 For each test item, theexaminer must identify and observe 3 key descriptors:weight bearing, posture, and antigravity movement. Thecontent and key descriptors for each item have beendescribed in detail.26 The recently revised BSID-II con-tains the Motor Scale (111 items), the Mental Scale (178items), and the Behavioral Rating Scale (30 items).12

The instrument was normed on 1,700 infants, aged 1through 42 months, and reliability and validity wereestablished in the United States.12 The interrater reliabil-ity for the BSID-II on full-term and preterm Taiwaneseinfants was established by our research team (percentageof agreement greater than .90). The content and criteriafor each item are described in the manual.12 The con-trast of the administration and scoring criteria for com-parable test items (ie, Supported Standing [3] versusSupports Weight Momentarily) between the AIMS andthe Bayley Motor Scale is presented in Table 1.

Table 1.Contrast of Administration and Scoring Criteria for Comparable Test Items Among the Alberta Infant Motor Scale and the Bayley Motor Scalea

Test ItemDescription

Supported Standing (3)(Alberta Infant Motor Scale)

Supports Weight Momentarily(Bayley Motor Scale)

Administration Stand the child on the floor and support him orher at chest level.

Stand the child on the floor and hold his or her hands so thatthe arms are extended at shoulder height. If the child appearsable to support his or her weight while standing, slowlyloosen your hold on the child according to his or her abilityto stand unsupported. Observe the child to determine whetherhe or she stands momentarily, using your hands for balancebut not for support.

If the child stands momentarily and supports his or her weight,slowly remove your hands and observe the child to determinewhether he or she stands alone.

Keep your hands close to the child in case he or she losesbalance.

Key descriptors andscoring criteria

Weight bearing: Weight on feet. Give credit if the child supports his or her own weight at leastmomentarily (for at least 2 seconds), using your hands forbalance only.

Posture: Head in midline, hips in line withshoulders, and hips abducted and laterally(externally) rotated.

Antigravity: Active control of trunk and variable

movements of legs: may bounce up anddown, lift one leg, or hyperextend the knees.

To pass this item, the infant must have the heelsdown at some point during the observationperiod and demonstrate spontaneousmovement in the legs.

aAdapted and reproduced with permission from Motor Assessment of the Developing Infant26 and from Bayley Scales of Infant Development, 2nd ed,12 (copyright 1993

by The Psychological Corporation, a Harcourt Assessment Company, all rights reserved). Bayley Scales of Infant Development is a registered trademark of The

Psychological Corporation.



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Six physical therapists (raters A, B, C, D, E, and F) servedas the AIMS raters. The therapists had 3 to 5 years ofexperience in the evaluation and treatment of pediatricpatients, but they had no prior experience in the admin-istration of the AIMS. They undertook a 32-hour train-ing course in understanding the theories of motordevelopment and administration and scoring of theAIMS. The theories of motor development included theneuromaturational and dynamical systems theories. The

section on administration and scoring of the AIMSprovided instructions and demonstrations of the testingprocedures and rating criteria of the scale. Following thetraining session, therapists were required to perform theAIMS on several normally developing full-term infantsand preterm infants. All therapists patient assessmentswere required to be in agreement with an experiencedinstructors assessments on at least 90% of the itemsprior to study. Due to our training session and practiceto achieve a level of agreement, our results may notreflect those obtained by therapists in general practice.

The data obtained for the infants examined during thetraining sessions were not included in the final analysisof reliability and validity. A psychologist who had 6months of experience in the administration of theBSID-II served as the BSID-II rater. Her patient assess-ments agreed with an experienced psychologists assess-ments on 90% of the items.

In the reliability study, the AIMS was administered to theinfants by a physical therapist (rater A), and infantperformance was videotaped by a videographer through-out the examination. To examine intrarater reliability,rater A scored the infant performance while administer-

ing the examination and rescored on the videotapes 1month later. This time interval was considered longenough to minimize the memory bias of the rater. Toexamine interrater reliability, 2 physical therapists (rat-ers B and C) observed the videotapes and independentlyscored the performance of the infants. Because of ouruse of a videotape, each rater did not have to handle thechild. This eliminated one potential source of error. Ingeneral practice, differences in handling skills between

therapists may lead to lower reliability.

In the validity study, the AIMS and the BSID-II wereadministered to the infants at corrected ages of 6 and 12months. Both tests were conducted within 1 week of theinfants 6- and 12-month birthdays, with an interval of 1to 7 days between tests. The AIMS was administered by 1of the 6 physical therapists, and the BSID-II was admin-istered by the psychologist. During the study period, nodiscussion was allowed between the physical therapistsand the psychologist to ensure that the scorings of the 2tests were independent and free from bias.

Data AnalysisIntrarater and interrater reliability were examined usingthe intraclass correlation coefficient (ICC) and thestandard error of measurement (SEM). The ICC pro-vides an estimate of the degree of agreement betweenobserved test scores. It was derived from the random-effects analysis of variance models in which subjects andraters were treated as independent factors.41,42 The SEMprovides an estimate of the amount of error in anindividuals observed test score. It was calculated asSD lr, where SD was the sample standard deviationand r was the correlation coefficient.43

Table 2.Characteristics of Subjects Included in the Reliability and Validity Studiesa

CharacteristicReliability Study(n 45)

Validity Study(n 41)

Male sex (%) 60.0 51.2

Inborn (%) 93.3 100.0

Gestational age (wk) 31.53.0 (26 36) 30.22.8 (2436)

Birth weight (g) 1,523.4508.4 (6862,906) 1,135.8233.7 (6301,500)

Intrauterine growth retardation (%) 33.3 53.7

Apgar score1 min 5.72.3 (19) 4.42.7 (09)5 min 7.91.5 (410) 7.12.0 (110)

Intraventricular hemorrhage status (%)Grade III 15.6 17.1Grade IIIIV 4.4 2.4

Chronic lung disease (%) 26.7 34.1

Duration of hospital stay (d) 61.655.5 (2265) 64.125.0 (30122)

a The data are presented as the meanSD (range in parentheses) or percentage. Inborn indicates that the child was born at the National Taiwan University

Hospital, compared with outborn, indicating that the child was born at another hospital and was transferred to the National Taiwan University Hospital.




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The concurrent validity of the AIMS with the BayleyMotor Scale was determined by the correlation betweenthe AIMS total scores and the Bayley Motor Scale rawscores at 6 and 12 months. The predictive validity of theAIMS scores was determined by the correlation betweenthe 6-month AIMS total scores and the 12-month BayleyMotor Scale raw scores. The correlations were analyzed

using Pearson product-moment correlation coefficients.

In our opinion, the levels of reliability described byPortney and Watkins37 and the levels of validitydescribed by Meyer44 are accurate indicators of theextent of reliability and validity. The extent of reliabilitywas determined as follows: correlation coefficientsgreater than .90 indicated high reliability, valuesbetween .75 and .90 indicated good reliability, valuesbetween .50 and .75 indicated moderate reliability, andvalues below .50 indicated poor reliability.37 The extentof validity was determined as follows: correlation coeffi-cients greater than .80 indicated high validity, valuesbetween .60 and .80 indicated good validity; valuesbetween .40 and .60 indicated moderate validity, andvalues below .40 indicated poor validity.44 All statisticalanalyses were performed with the use of the StatisticalAnalysis Software program.

Results

Intrarater and Interrater ReliabilityThe results of the intrarater reliability study for the 3 agegroups are presented in Table 3. For the total scores, theSEMs between the first and second scores were less than

1.3 points, and the ICCs were greater than .95 across allage groups (P.0001). For the subscale scores, theSEMs of the repeated scores were less than 0.9 point,and the ICCs ranged from .85 to .99 for all age groups(P.0001). Of the 4 subscales, the correlation coeffi-cients were the lowest for scores when the childrenwere standing.

The independent scorings of the AIMS by raters A, B,and C and interrater reliability values for the 3 agegroups are shown in Table 4. For the total scores, theSEMs between raters were less than 1.3 points, and the

ICCs were greater than .95 across age groups (P.0001).For the subscale scores, the SEMs between raters wereless than 0.8 point for all age groups. Correlationanalysis indicated ICCs for most subscales across agegroups to be greater than .90 (P.0001). The ICCs forthe standing scores were .98 for infants 8 months of ageor older (P.0001), .73 in the 0- to 3-month-old group(P.0001), and .75 in the 4- to 7-month-old group(P.0001). The distributions of scorings by individualraters among the early standing items are presented for

the 0- to 3-month-olds and the 4- to 7-month-olds inTable 5.

Concurrent and Predictive Validity

Infants in the validity study achieved AIMS total scores(XSD) of 25.44.9 and Bayley Motor Scale raw scoresof 33.44.9 at 6 months of age. At 12 months of age,they attained AIMS total scores of 49.77.9 and BayleyMotor Scale raw scores of 58.05.2.

Correlation analysis revealed a Pearson r of .78 betweenthe 6-month AIMS total scores and the 6-month BayleyMotor Scale raw scores (P.0001) and a Pearson rof .90between the 12-month AIMS total scores and the12-month Bayley Motor Scale raw scores (P.0001).That is, the 6-month AIMS total scores and the 6-monthBayley Motor Scale raw scores shared about 61%

(r2.61) of the total variance, whereas the 12-monthAIMS total scores and the 12-month Bayley Motor Scaleraw scores shared about 81% (r2.81) of the total variance.

The correlation (r) between the 6-month AIMS totalscores and the 12-month Bayley Motor Scale raw scoreswas .56 (P.001). There were correlations (r) of .51between the 6- and 12-month scores within the AIMS(P.001) and .53 within the Bayley Motor Scale(P.001).

SAS Institute Inc, PO Box 8000, Cary, NC 27511.

Table 3.Repeated Scorings by Rater A and Intrarater Reliability as Determinedby Standard Errors of Measurement (SEMs) and Intraclass CorrelationCoefficients (ICCs)a

Age Groupand Subscale

FirstScoring

SecondScoring SEM ICC

03 mo (n15)Prone 3.12.0 2.92.2 0.40 .96Supine 3.30.6 3.30.7 0.17 .92Sitting 1.71.1 1.71.1 0.31 .92Standing 1.60.6 1.70.7 0.23 .85Total 9.73.9 9.74.0 0.55 .98

47 mo (n15)Prone 9.74.1 9.73.9 0.82 .96Supine 7.22.0 7.22.0 0.53 .93Sitting 5.82.7 5.82.3 0.54 .96Standing 2.81.0 2.91.0 0.32 .90Total 25.58.8 25.68.2 1.24 .98

8 mo or older (n15)Prone 17.25.4 17.15.5 0.05 .99Supine 8.51.3 8.51.3 0.01 .99Sitting 10.33.1 10.13.2 0.44 .98Standing 8.04.2 7.94.1 0.73 .97Total 44.013.0 43.513.1 0.13 .99

a The subscale and total scores are presented as the meanSD. The units for

test scores and SEMs are points. All ICCs had probability values of less than

.0001 (F14,15).



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Discussion

ReliabilityOur results, in our opinion, showed high levels of

intrarater and interrater reliability (ICCs greater than.95) for the total scores of the AIMS when used onpreterm infants from birth to age 18 months. The SEMsand reliability coefficients were similar to those reportedfor full-term Canadian infants.26 The findings indicatethat physical therapists in Taiwan, after a 32-hour train-ing course in understanding the theories of motordevelopment and administration and scoring of theAIMS, can reliably replicate their own and other thera-pists assessments of preterm infants.

We compared the reliability values among the 4 subscalescorings in 3 age groups. The SEMs were small (less than1.50 points) for all subscale scorings across age groups.The correlation coefficients were, in our view, high formost subscale scorings, except for those of the standingscores of the 0- to 3-month-olds and the 4- to 7-month-olds. The lower correlations of standing scores in theyounger infants may be attributed to 2 factors: the smallvariability in test scores among the subjects and the diffi-culty in assessing early standing movements in infants.

The younger infants exhibited such a narrow range ofscores that their standing performance was rated asSupported Standing (1), Supported Standing (2), or

Supported Standing (3) on the scale. The ICC is

defined as the ratio of the adjusted variance among thesubjects to the sum of the variance among the subjectsand error variance.41 The small variability among thesubjects for standing scores may thus attenuate the corre-lation coefficient values in the younger age groups.42

The difficulty in assessing the early standing movementsin preterm infants may also contribute to the lowerreliability for the standing scorings. According to theitem descriptions of the AIMS, the major componentsfor the acquisition of early standing movements arepostural stability and mobility of the neck, trunk, shoul-

ders, and lower extremities in various movement planes(Tab. 1).26 Transitions from one standing movement toanother (ie, from Supported Standing [1] to Sup-ported Standing [2] and from Supported Standing[2] to Supported Standing [3]) in a normally devel-oping young child, therefore, require a high degree ofcoordination in those components.45 The describedscoring criteria, however, appeared to have limited sen-sitivity in detecting the subtle differences in the earlystanding movements of preterm infants in Taiwan.Future study is necessary to determine whether similarproblems exist for the application of the AIMS oninfants of different ethnicities.

ValidityOur results showed what we would consider good to highdegrees of correlation between the AIMS scores and theBayley Motor Scale scores when the 2 tests were concur-rently applied on preterm infants. The correlation valueswere slightly lower than the data (r.84 and .93)reported by Piper and Darrah.26 The discrepancies maybe due to sampling bias or methodological differences.Piper and Darrah26 had the same assessor to perform theAIMS and the Bayley Motor Scale on infants, whereas wehad different assessors administer the 2 tests on infants.

Table 5.Distributions of Scorings by Raters A (First and Second Scorings), B,and C Among the Three Supported Standing Items in the 0- to 3-Month-Old Infants and the 4- to 7-Month-Old Infants

Age Groupand Test Item

Rater A

RaterB

RaterC

FirstScoring

SecondScoring

03 mo (n15)Supported standing (1) 7 6 6 5Supported standing (2) 7 7 9 10Supported standing (3) 1 2 0 0

47 mo (n15a)Supported standing (1) 0 0 0 0Supported standing (2) 6 5 8 6Supported standing (3) 8 9 6 8

a The standing performance of one infant was rated as cruising without

rotation.

Table 4.Scorings by Raters A, B, and C and Interrater Reliability asDetermined by Standard Errors of Measurement (SEMs) and IntraclassCorrelation Coefficients (ICCs)a

Age Groupand Subscale Rater A Rater B Rater C SEM ICC

03 mo (n15)Prone 2.92.2 2.91.8 2.91.9 0.49 .94Supine 3.30.7 3.10.8 3.30.7 0.16 .93Sitting 1.71.1 1.91.1 1.91.2 0.25 .95Standing 1.70.7 1.60.5 1.70.5 0.31 .73Total 9.74.0 9.53.5 9.73.6 0.68 .97

47 mo (n15)Prone 9.73.9 9.53.5 9.93.5 0.71 .97Supine 7.22.0 7.31.8 7.31.8 0.40 .96Sitting 5.82.3 5.42.1 5.72.3 0.47 .97Standing 2.91.0 2.60.8 2.70.8 0.50 .75Total 25.68.2 24.97.3 25.77.6 1.24 .98

8 mo or older(n15)

Prone 17.15.5 16.95.4 17.15.2 0.05 .99Supine 8.51.3 8.51.3 8.51.3 0.01 .99Sitting 10.13.2 10.13.1 10.13.0 0.44 .98Standing 7.94.1 7.54.0 7.94.2 0.59 .98Total 43.513.1 43.112.8 43.712.7 0.13 .99

a The subscale and total scores are presented as the meanSD. The units for

scorings and SEMs are points. All ICCs had probability values of less than

.0001 (F14,2).




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In contrast to Piper and Darrahs study design, our studydesign eliminated the bias of the raters temptation ofgiving similar ratings on the target and criterion tests,which may result in lower correlation values.37

The congruency between the AIMS scores and theBayley Motor Scale scores was found to be stronger at 12

months than at 6 months. This difference may relate, inpart, to the uneven distribution of gross and fine motortest items in the Bayley Motor Scale to adequatelyevaluate motor skills at all age levels in infancy. TheBayley Motor Scale consists of 91 gross motor test itemsand 20 fine motor test items.12 There are 8 fine motorskill items for the 4- to 8-month age period, whereasthere are only 4 fine motor skill items for the 10- to14-month age period. The inclusion of primarily grossmotor items in the Bayley Motor Scale at the 10- to14-month age period may predispose Bayley Motor Scalescores to a high degree of correlation with AIMSscores, as the latter scale was constructed to assessgross motor behaviors.

The obtained congruency between the AIMS scores andthe Bayley Motor Scale scores suggests that physicaltherapists may choose between the 2 scales to evaluatemotor function of premature infants. The AIMS mightbetter fulfill the current need in the field of infant motorassessment because the process and quality of movementas well as the achievement of specific milestones areconsidered. Furthermore, the ease of administration of theAIMS may make this instrument more feasible for use infollow-up clinics for infants at risk for motor delays.

The prognostic value of the 6-month AIMS scores inpredicting the 12-month Bayley Motor Scale scores wasonly moderate. Our findings are consistent with the dataestablished on the Canadian sample.27 Limited predic-tive validity has also been documented for several infantmotor tests, including the Movement Assessment ofInfants,46,47 the Bayley Motor Scale,4850 and the Pea-body Developmental Motor Scales.48 These results sug-gest that wide variability exists in the maturationalcourse of motor ability in preterm infants during the firstyear of life.

Several factors may contribute to the instability in theearly motor developmental scores of preterm infants.First, perinatal insults such as birth asphyxia,51 intra-uterine growth retardation,52 intraventricular hemor-rhage,53 and chronic lung disease54 can adversely affectneuromotor development. Recovery from these perina-tal events, however, may be accompanied by rapidprogress in neuromotor function, with concomitantimprovement in motor scores.46,55 Second, variations inthe age of onset and the rate of resolution of transientneuromotor abnormality, which affects about 60% of

infants with very low birth weights, may also add to theinstability.47,5659 Finally, there is tremendous variabilityin the rates of neuromotor development among infants.Longitudinal follow-up studies of mental and motordevelopment in infants at high risk for motor delays andin normally developing infants consistently show low tomoderate degrees of stability in developmental

scores.28,4650

Not only do the rates of developmentdiffer among infants, but there are also intraindividualvariations in the rates of development at various timesduring childhood. Evidence from a twin study60 suggeststhat the differences in the patterns of neuromotorprogress among individuals may be determined to someextent by genetic factors.

ConclusionThe results of this study demonstrated high degrees ofintrarater and interrater reliability for the AIMS whenapplied on preterm infants aged from birth to 18months. Good to high degrees of concurrent validitywere also found for the scale, using the Bayley MotorScale as the criterion measure. The prognostic value ofthe AIMS was shown to be only moderate, however, inpredicting the motor outcome of preterm infants at 1year of age. Our results indicate that the AIMS providesreliable and valid measurements that can be used for theevaluation of the current motor function of preterminfants in Taiwan. Physical therapists should be cautious,however, in using the test scores at the earlier ages topredict later developmental outcome. The comparableestimates of reliability and criterion-related validity forthe AIMS between the Taiwanese and Canadian samples

suggest that the AIMS could be used cross-culturally forthe evaluation of infant movement. Future study isneeded to establish the normative data for the AIMS inTaiwan to provide the basis for discriminating motorfunction of normally developing infants from that ofinfants with motor delays. In addition, more work needsto be done on the issues related to predictive validity forthe AIMS.

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2000; 80:168-178.PHYS THER.Shu-Fang HsiaoSuh-Fang Jeng, Kuo-Inn Tsou Yau, Li-Chiou Chen andWhen Used on Preterm Infants in TaiwanAlberta Infant Motor Scale: Reliability and Validity

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