discapacidad intelectual dsm

To ID or Not to ID? Changes in Classification Rates ofIntellectual Disability Using DSM-5

Aimilia Papazoglou, Lisa A. Jacobson, Marie McCabe, Walter Kaufmann, and T. Andrew Zabel

AbstractThe Diagnostic and Statistical Manual of Mental Disorders—Fifth Edition (DSM-5) diagnostic criteriafor intellectual disability (ID) include a change to the definition of adaptive impairment. Newcriteria require impairment in one adaptive domain rather than two or more skill areas. The authorsexamined the diagnostic implications of using a popular adaptive skill inventory, the AdaptiveBehavior Assessment System–Second Edition, with 884 clinically referred children (ages 6–16).One hundred sixty-six children met DSM-IV-TR criteria for ID; significantly fewer (n 5 151,p 5 .001) met ID criteria under DSM-5 (9% decrease). Implementation of DSM-5 criteria for IDmay substantively change the rate of ID diagnosis. These findings highlight the need for acombination of psychometric assessment and clinical judgment when implementing the adaptivedeficits component of the DSM-5 criteria for ID diagnosis.

Key Words: adaptive functioning; intellectual disability; mental retardation; DSM-IV; prevalence

The diagnosis of intellectual disability (ID; formerlyknown as mental retardation) is characterized byconcurrent deficits in intellectual and adaptivefunctioning, with onset prior to adulthood. Preva-lence rates for ID are generally estimated to be 1% ofthe population, with higher rates in middle and low-income countries (Maulik, Mascarenhas, Mathers,Dua, & Saxena, 2011). In the United States, thisamounts to approximately 3 million people (Larsonet al., 2001), with more than 543,000 children (ages6–21) identified by the public school system as havingsome level of ID (U.S. Department of Education,2007). A diagnosis of ID has a number of importantimplications, including eligibility for supports such asacademic services, residential placement, vocationalsupport, and Social Security Disability, as well asineligibility for capital punishment.

The definition of ID has undergone manyrevisions. Initially, ID referred only to impairmentsin intellectual functioning; however, in 1959,impairments in age-appropriate day-to-day function-ing (adaptive functioning) formally became part ofthe definition (Heber, 1959, 1961). More recentdiagnostic formulations of ID have maintained therequirements for deficits in both intellectual abilityand adaptive functioning. In the Diagnostic andStatistical Manual of Mental Disorders—Fourth Edition

(Text Revision; DSM-IV-TR), the intellectualimpairment component of the diagnosis of IDwas defined as ‘‘significantly subaverage intellectualfunctioning: an IQ of approximately 70 or below’’(American Psychiatric Association, 2000, p. 49).Based largely upon the definition of adaptivefunctioning proposed by the American Associationof Intellectual and Developmental Disabilities(AAIDD, formerly known as the American Associ-ation on Mental Retardation; Luckasson et al.,1992), DSM-IV-TR defined adaptive functioningdeficits as concurrent impairments (e.g., perfor-mance approximately 2 standard deviations [SD]below the mean) in at least two theoretically derivedadaptive skill areas (i.e., communication, self-care,home living, social/interpersonal skills, use of com-munity resources, self-direction, functional academicskills, work, leisure, health, and safety; AmericanPsychiatric Association, 2000). Of note, there issome debate about whether there are 10 or 11adaptive skill areas depending on whether or nothealth and safety are considered distinct skill areas.Subsequently, broader factors or adaptive domainscomposed of these individual adaptive skill areaswere described (e.g., Greenspan, 1999; Harrison &Oakland, 2003; Luckasson et al., 2002; Thompson,McGrew, & Bruininks, 1999). These three broad

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A. Papazoglou et al. 165

domains (i.e., Conceptual, Social, Practical) havesince been incorporated into the AAIDD descrip-tion of adaptive functioning (Luckasson et al., 2002;Schalock et al., 2010).

The fifth edition of the DSM (DSM-5; AmericanPsychiatric Association, 2013) includes a change inthe name of the disorder, a revision of the diagnosticcriteria, and changes in the severity specifiers.Consistent with the AAIDD’s and the internationalcommunity’s shift from the term mental retardation tointellectual disability, DSM-5 uses the term intellectualdisability coupled with the term intellectual developmen-tal disorder (to be consistent with InternationalClassification of Diseases, 11th Edition). As was the casewith DSM-IV, DSM-5 diagnostic criteria for IDspecify evidence of intellectual and adaptive impair-ment during the developmental period. DSM-5criteria pertaining to intellectual impairment aresimilar to those of DSM-IV and stipulate deficits in‘‘general mental abilities such as reasoning, problem-solving, planning, abstract thinking, judgment, aca-demic learning, and learning from experience,’’defined as an IQ of approximately # 70 (6 5 pointsfor error; American Psychiatric Association, 2013,p. 37). The DSM-5 criteria pertaining to deficits inadaptive functioning, however, have been moresignificantly modified. Specifically, adaptive impair-ment is defined as follows (American PsychiatricAssociation, 2013):

Deficits … that result in failure to meetdevelopmental and sociocultural standards forpersonal independence and social responsibil-ity (p. 33).…[The criterion] is met when atleast one domain of adaptive functioning—conceptual, social, or practical—is sufficientlyimpaired that ongoing support is needed inorder for the person to perform adequately inone or more life settings at school, work, homeor in the community. (p. 38)

In contrast to DSM-IV, which stipulated impair-ments in two or more skill areas, DSM-5 criteriadenote impairment in one or more superordinatedomains of adaptive functioning (e.g., Conceptual,Social, Practical).

DSM-5 also redefines how ID severity isdetermined. DSM-IV-TR defined severity on thebasis of IQ test scores (mild, moderate, severe,or profound). These same levels of severity areretained; however, in DSM-5 ‘‘the various levels ofseverity are defined on the basis of adaptive

functioning, and not IQ scores, because it isadaptive functioning that determines the level ofsupports required. Moreover IQ measures are lessvalid in the lower end of the IQ range’’ (AmericanPsychiatric Association, 2013, p. 33).

For diagnostic purposes under DSM-5, deficitsin adaptive functioning are still established by wayof clinical evaluation and administration of psy-chometrically sound measures, such as question-naires that elicit observer or informant ratings of anindividual’s typical level of independent func-tioning (McCarver & Campbell, 1987). Of note,however, DSM-5 provides a table offering addi-tional guidance for determining severity of adaptiveimpairment (i.e., mild, moderate, severe, andprofound) within Conceptual, Social, and Practicaldomains. This table is intended to assist indetermination of severity of adaptive impairment,although no specific guidance is given regarding theuse of test scores for the determination of severityspecifiers (e.g., the mild range of ID is not definedby a test score range). Clinicians are encouraged touse ‘‘both clinic evaluation and individualized,culturally appropriate, psychometrically sound mea-sures’’ (American Psychiatric Association, 2013,p. 37), and to use clinical judgment when interpret-ing scores from these measures.

One such standardized observer–informantreport instrument is the Adaptive Behavior Assess-ment System—Second Edition (ABAS-II; Harrison& Oakland, 2003), which is a commonly usedmeasure of adaptive functioning on which acaregiver rates the individual’s level of independentfunctioning on multiple items across skill areas.The parent form is used for children ages 5–21 yearsand provides estimates of the child’s functioningacross 9 skill areas (or 10 skill areas if he or she isemployed). Scale composition of the first edition ofthe ABAS (Harrison & Oakland, 2000) wassubstantively influenced by the definition ofadaptive functioning proposed by the AAIDD andothers (e.g., Luckasson et al., 1992; Thompsonet al., 1999), as well as the diagnostic criteria inDSM-IV. The skill areas were maintained in thepublication of the second edition (ABAS-II;Harrison & Oakland, 2003), but in keeping withthe existing body of research (e.g., Greenspan,1999; Harrison & Oakland, 2003; Luckasson et al.,2002; Thompson et al., 1999) and the revised IDconceptualization proposed by the AAIDD, theseskill areas were further organized into three broadadaptive skill domains: Conceptual, Practical, and


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166 Intellectual Disability and DSM-5

Social. The ABAS-II domains have increasedrelevance with the publication of DSM-5, as theymap onto the new adaptive domain modelpresented in DSM-5. Of note, the ABAS-IIgroupings of the individual skill areas into domainscales were modeled on theoretical foundationsbased in earlier research, and were not based onexploratory factor loadings. Subsequently, confir-matory factor analysis of the ABAS-II has yieldedonly modest support for this three-factor model(Wei, Oakland, & Algina, 2008), and there isevidence to suggest that the most parsimonious fitto the data is a one-factor solution (Harrison &Oakland, 2003). To date, there has been littleresearch on the appropriateness of the 9 and 10 skillarea factors.

The aim of this study was to examine thepotential impact of the DSM-5 diagnostic criteriaon classification rates of ID. There is the potentialfor a ‘‘gray zone’’ in which individuals meet IDcriteria under the DSM-IV-TR criteria (i.e., im-pairment in two or more skill areas) but not underDSM-5 criteria (i.e., impairment in one or moredomains), particularly when psychometric measuressuch as the ABAS-II are used as the primary meansto quantify deficits in adaptive functioning. Forinstance, under the ABAS-II factor structure,individuals with skill deficits in home living andself-care might still qualify for ID, as both of theseskills are grouped under the Practical domainfactor. In contrast, an individual with skill deficitsin social skills and functional communicationmight not, as these skill areas are grouped intodifferent domain factors. Clarification of a possiblediagnostic drift in ID diagnoses is valuable, as theimplications for the educational (i.e., eligibility forspecial education services), social (i.e., eligibilityfor entitlement services and funding), and legal(i.e., capital punishment decisions) systems may beprofound. To this end, we examined ID classifica-tion rates using a psychometric definition ofimpairment as two or more skill areas (DSM-IV-TR criteria) and one domain area (DSM-5 criteria),with adaptive impairment defined as standardizedscores $ 2 SD below the mean. Given persistentquestions about the factor structure of the ABAS-II, we hypothesized that, when compared withclassification rates of ID using DSM-IV-TR criteria,diagnosis based on psychometrically defined im-pairment in one domain (DSM-5 criteria) has thepotential to result in significantly fewer childrenmeeting criteria for ID.

Methods

ParticipantsFor the purposes of this study, de-identified patientrecords from the clinical database of the Depart-ment of Neuropsychology at the Kennedy KriegerInstitute, a large medical institute serving youthwith developmental disabilities in the mid-Atlanticregion, were reviewed. Data are routinely enteredinto this database by department clinicians via theelectronic health record, and are securely main-tained by the information systems department.After approval by the Johns Hopkins Hospitalinstitutional review board, a limited dataset wasconstructed of patients between the ages of 6 and16 years for whom valid scores on both intellectual(e.g., Wechsler Intelligence Scales for Children—Fourth Edition, WISC-IV; Wechsler, 2003) andadaptive (e.g., ABAS-II; Harrison & Oakland,2003) measures were available. The final sampleincluded 884 children (mean age 5 10.49, SD 5

2.80; 67% male), for whom records includedWISC-IV and ABAS-II scores, age at time ofassessment, ethnicity, and sex. All patients includ-ed in the dataset had been referred for outpatientneuropsychological assessment. Of these 884 chil-dren and adolescents, 203 had a Full Scale IQ(FSIQ) that was $ 2 SD below the mean (FSIQ #

70), representing 23% of the total clinicallyreferred sample.

MeasuresABAS-II. The ABAS-II is a parent-report

questionnaire assessing whether an individualindependently displays the functional skills neces-sary for age-appropriate daily living. The ABAS-IIdivides adaptive functioning into nine skill areas,which are subsumed under three theoreticallyderived domains: the Conceptual Domain (Com-munication, Functional Academics, and Self-Di-rection skill areas), Social Domain (Leisure andSocial skill areas), and Practical Domain (Commu-nity Use, Home Living, Health and Safety, andSelf-Care skill areas). A 10th skill area, Work skills,can be administered to older adolescents and youngadults who are employed, but it was not included inthis study given the age range of the sample. Thenine primary skill areas can be used to generate aGeneral Adaptive Composite (GAC). As noted inthe test manual (Harrison & Oakland, 2003), theABAS-II GAC has strong internal consistency(a 5 .98) as do the domain (a 5 .86–.93) and skill


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area scores (a 5 .95–.97). Stability over time (M 5

12 days, SD 5 10 days) is strong (GAC correctedtest–retest reliability r 5 .93, domain correctedtest–retest r 5 .89–.93, skill area corrected test–retest r 5 .84–.92). The ABAS-II also hasdemonstrated adequate validity in a sample ofchildren with ID (e.g., mean GAC scores in a groupof 41 individuals between the ages of 5 and 21diagnosed with ID, of unspecified severity, wasequal to 63.7, mean skill area scaled scores rangedfrom 3.7 to 5.5). Of note, 82.93% of theseindividuals with ID had two or more individualskill area scores that fell at or below 22 SD, while80.49% of these same individuals had one or moreadaptive domain scores that fell at or below 22 SDbased on caregiver report. Because the sample isdescribed as ‘‘unspecified,’’ there is no way toexamine these data at various levels of intellectualimpairment (e.g., mild versus moderate intellectualability). However, although statistical significancewas not reported, there was a trend toward a higherpercentage of impaired skill area scores reported forindividuals with mild ID in the validity data for theteacher version of the ABAS-II. Specifically, of the66 individuals with mild ID who were rated by theirteachers on the ABAS-II, 75.76% had two or moreindividual skill areas scores that fell at or below 22SD, while only 60.61% of these same individualshad one or more adaptive domain scores that fell ator below 22 SD (Harrison & Oakland, 2003).

Two other commonly used measures of adap-tive functioning are the Vineland Adaptive Be-havior Scales, Second Edition (VABS-II; Sparrow,Cicchetti, & Balla, 2005) and the Scales ofIndependent Behavior, Revised (SIB-R; Bruininks,Woodcock, Weatherman, & Hill, 1996). Correla-tions between the ABAS-II GAC and VABS-IIAdaptive Behavior Composite were moderatelyhigh (r 5 .78), with correlations at the subdo-main/skill area level mostly falling in the 0.50range. Correlations between the ABAS-II GACparent version and the Early Development Form ofthe SIB-R Broad Independence Score were low (r5 .18), while the correlation between the ABAS-IIGAC teacher-version and the Short Form of theSIB-R Broad Independence Score were stronger(r 5 .59).

WISC-IV. The WISC-IV is a widely acceptedmeasure of intellectual ability with adequatepsychometric properties for identifying childrenwith ID. The WISC-IV provides a global intellec-tual estimate, the FSIQ. The FSIQ has shown

excellent internal reliability and stability over time(e.g., internal consistency estimates [split-half]yield an FSIQ r 5 .97; corrected test–retest r 5

.93). The WISC-IV FSIQ also has demonstratedadequate validity for use with this population(Wechsler, 2003).

Experimental DesignFirst, we examined the pattern of associationsbetween measures of intellectual and adaptive skillareas. Next, the total number of children who metstrict DSM-IV-TR criteria for ID was identified(i.e., WISC-IV FSIQ # 70, with two or more skillareas on the ABAS-II # scaled score of 4). Thetotal number of children who met the psychomet-rically defined DSM-5 criteria was then calculated(i.e., WISC-IV FSIQ # 70, with one or moredomains on the ABAS-II # 70). The McNemartest was used to compare the differences in theproportion of individuals classified as ID based onthe changing criteria for adaptive impairment.

Results

Of the 203 children with FSIQ # 70, 166 metDSM-IV-TR criteria for adaptive impairment, thatis, impairment in two or more skill areas. On thebasis of DSM-5 criteria for adaptive impairment(i.e., impairment in one or more adaptive domains),151 children met criteria for ID. This represents anet loss of 15 children. Sixteen children met DSM-IV-TR criteria but not DSM-5 criteria, and onechild met DSM-5 criteria but did not meet DSM-IV-TR criteria. This net difference of 15 childrenrepresents a statistically significant 9% decrease inthe number of children who met criteria for IDunder DSM-5 as compared to DSM-IV-TR (McNe-mar test x2 5 122.02, p 5 .001). Mean scores onthe ABAS-II and WISC-IV for the children whomeet DSM-IV-TR and DSM-5 criteria for adaptiveimpairment are presented in Table 1.

In the total clinically referred sample (N 5

884), there was a broad range of correlationsbetween FSIQ and individual skill areas on theABAS-II. The strongest correlations were notedbetween FSIQ and the ABAS-II FunctionalAcademics (r 5 .56, p , .001) and Communica-tion (r 5 .39, p , .001) skill area scales. All of theremaining seven ABAS-II skill area scales also weresignificantly correlated with FSIQ (p , .001), withcorrelations ranging from r 5 .13 to r 5 .32. Eachof the composite domain scales of the ABAS-II was


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significantly correlated with FSIQ (all p , .001),with the strongest correlations noted with theConceptual domain (r 5 .48) as compared to theSocial (r 5 .31) and Practical (r 5 .32) domains. Inchildren with FSIQ # 70, the frequency ofimpaired scores (i.e., scaled score # 4) on theABAS-II skill area scales was as follows: HomeLiving (70%), Self-Direction (68%), Social (66%),Functional Academics (58%), Self-Care (56%),Community Use (51%), Communication (46%),Health and Safety (45%), and Leisure (35%). Inthis group, impaired domain scores (standard scores# 70) were most frequently found on theConceptual (62%) and Practical (62%) compositesand were less frequently observed on the Socialcomposite (48%).

Data on the 17 children whose status changedwith the shift to DSM-5 criteria are presented inTable 2. Bold font is used to denote children whowere impaired in ABAS-II skill areas. The onechild who met DSM-5, but not DSM-IV, criteriawas impaired on the Conceptual domain and had asingle area of skill area impairment (Communica-tion), with three other skill areas in the borderline-impaired range. Of the 16 children who met DSM-IV, but not DSM-5, criteria, 100% had a FSIQ of# 70, 25% had a Verbal Comprehension Index of# 70, 38% had a Perceptual Reasoning Index of# 70, 81% had a Working Memory Index of # 70,and 88% had a Processing Speed Index of # 70.The majority of these children had two skill areasimpaired (69%), with 19% impaired on three skillareas, and 12% impaired on four skill areas. Home

Living was most likely to be impaired (56%),followed by Communication (38%), FunctionalAcademics (38%), Self-Care (31%), Social (31%),Self-Direction (19%), Community Use (19%), andHealth & Safety (12%). No children were impairedon Leisure.

Discussion

This study sought to investigate any potentialimpact on the rates of ID classification when anexisting and widely used adaptive functioningmeasure (ABAS-II) was used to psychometricallydetermine deficits in adaptive functioning based onimplementation of the new DSM-5 ID criteria. TheDSM-5’s use of adaptive impairment to quantifyseverity of ID highlights a renewed emphasis onadaptive functioning in this condition. There isconcern, however, that the diagnostic change fromadaptive skill deficits to adaptive domain deficitsmight make the diagnosis more restrictive due toinstrumentation and measurement issues, particu-larly when psychometric measures are used as theprimary means to quantify deficits in adaptivefunctioning. We hypothesized that, when using theABAS-II to psychometrically quantify adaptiveimpairment, fewer children would qualify for anID diagnosis when DSM-5 criteria were implement-ed (relative to DSM-IV). This was supported, as weidentified a potential 9% decline in the number ofchildren who met criteria for DSM-5 as comparedwith DSM-IV-TR in our large clinical sample. Ofnote, the children excluded by DSM-5 ID criteriahad milder degrees of adaptive impairment,

Table 1Descriptive Statistics

Variable

All children withFSIQ # 70(n 5 203)

DSM-IV: FSIQ andtwo skill areas impaired

(n 5 166)

DSM-5: FSIQ andone domain impaired

(n 5 151)

Age in years 11.32 (2.73) 11.35 (2.69) 11.38 (2.71)

Percent male 66 67 68

Percent White: African American:

Other: Unknown 37: 42: 6: 15 38: 41: 7: 14 40: 38: 7: 15

WISC-IV FSIQ 60.25 (7.79) 59.49 (8.06) 59.15 (8.21)

ABAS-II GAC 66.22 (15.21) 61.10 (10.67) 59.28 (9.23)

ABAS-II Conceptual 68.88 (13.74) 64.82 (10.42) 63.15 (9.30)

ABAS-II Social 74.82 (15.63) 70.36 (12.44) 68.58 (11.10)

ABAS-II Practical 66.22 (15.22) 60.43 (15.27) 58.20 (14.26)

Note. Standard deviations are presented in parentheses. ABAS-II and WISC-IV scores are presented as standard

scores.


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Table

2S

tan

dard

ized

Sco

res

onth

eA

BA

S-I

Ian

dW

ISC

-IV

for

Chi

ldre

nW

hose

IDD

iagn

ostic

Cla

ssific

atio

nC

han

ges

With

the

Impl

emen

tation

ofD

SM

-5C

rite

ria

Age

(years)WISC-IV

FSIQ

VCIPRI

ABAS-II

GAC

Conceptual

Social

Practical

Commu-

nication

Communi-

cationUse

Functional

Academ

ics

Home

Living

Health

and

Safety

Leisure

Self-

Care

Self-Di-

rection

Social

Does

notmeetID

criteria

forDSM-IV,butdoes

meetcriteria

forDSM-5

10.92

50

57

59

78

67

84

87

27

56

11

57

58

Meetcriteria

forID

onDSM-IV-TR

butnotonDSM-5

13.75

67

89

73

75

72

90

79

66

55

76

24

9

13.17

65

83

75

79

75

90

82

98

65

10

83

17

14.58

54

73

57

82

78

97

81

77

63

11

10

49

9

14.33

67

79

73

88

91

100

83

10

11

93

10

10

36

11

8.75

68

69

88

69

72

81

75

68

12

67

46

5

12.58

56

75

55

85

86

92

87

86

43

11

78

99

11.42

59

79

57

84

87

93

82

13

74

49

86

510

8.5

70

73

71

77

88

72

79

97

74

65

67

4

11.42

70

89

73

84

72

105

86

710

61

712

11

210

8.42

56

59

73

76

81

96

72

36

52

38

89

10

10.67

64

79

61

85

80

97

87

410

64

910

88

9

7.92

61

75

73

80

83

87

85

32

911

710

75

4

7.42

60

65

71

82

81

72

95

49

78

11

67

53

8.42

52

57

61

69

75

72

78

37

36

45

58

4

12.67

69

77

86

70

72

78

78

24

46

59

69

2

13.08

55

77

51

82

80

93

82

91

48

76

10

511

Note.Boldface

indicates

childrenwithim

pairm

entonthesameskillarea

oftheABAS-II.WISC-IVandABAS-IIGACanddomainscoresarepresentedas

standardscores,

ABAS-IIskillarea

scoresarepresentedas

scaled

scores.

Abbreviation:VCI,Verbal

ComprehensionIndex;PRI,Perceptual

Reasoning

Index.


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although their profiles still indicated a high level ofadaptive and intellectual impairment. Given therelatively mild nature of their adaptive impairment,it is unclear whether these children and adolescentswould have been identified with ID during theDSM-IV-TR era, even though their IQ and ABAS-II scores were consistent with the diagnosticcriteria. As such, these data are of somewhatlimited value in anticipating the true impact ofDSM-5 on rates of ID. What these data dohighlight, however, is the need for clinicaljudgment when interpreting these scores, ratherthan a strict reliance upon scores from the currentpsychometric scale compositions.

When adaptive impairment is psychometricallydefined using ABAS-II scores, the children in oursample who would be ‘‘left out’’ of an ID diagnosisby the impaired domain criterion still showcompelling evidence of intellectual and adaptiveskill impairment. Among the children left out ofthe DSM-5 ID classification, their various combi-nations of adaptive skill area deficits tended to loadonto different domains (rather than a singledomain), resulting in domain level scores that wereabove a standard score of 70 in spite of the presenceof impairment in multiple skill areas. For instance,a child with skill area deficits in Communication,Social skills, and Community Use may experiencesignificant adaptive impairment, even though eachof these skill areas is grouped onto separate ABAS-II domains and these composite scores may fallwithin normal limits. Analysis of adaptive func-tioning in the 16 children who would be excludedfrom an ID diagnosis based on DSM-5 criteriarevealed that Home Living was the most commonlyimpaired skill area, followed by Communication,Functional Academics, Self-Care, and Social skills.These skill areas span all three of the ABAS-IIadaptive domains, and highlight the manner inwhich significant skill area deficits may be hiddenby grossly intact domain scores.

Given the common assumption that intellec-tual deficits contribute to deficits in adaptive skillsin youths with ID, it is not unexpected thatintellectual and adaptive functioning would besignificantly correlated. From a measurementperspective, however, it remains unclear whethera low score in an adaptive area that is highlycorrelated with IQ constitutes a distinct area ofadaptive deficit related to IQ rather than simply amultimethod approach to measuring the sameconstruct. This has, in fact, been a criticism of

the formulation of the diagnosis of ID in the past,as Greenspan (2006) and others have proposedthat the Conceptual composite of the ABAS-IIand its constituent skill area scales may measuremuch the same construct as an IQ test (i.e.,conceptual or academic intelligence). Indeed, inour sample of children with a FSIQ of # 70, IQwas most highly correlated with the Conceptualdomain (r 5 .30, p , .001), with smaller, albeitstill significant, correlations with the Practical(r 5 .27, p , .001) and Social (r 5 .18, p , .001)domains. As noted, the degree of variation incorrelation between IQ and adaptive domainscores not only raises a concern regarding multi-method assessment of the same construct (e.g., IQand Conceptual adaptive functioning), but alsoraises a question as to the relatedness of IQ andadaptive functioning in general. While eachABAS-II adaptive domain was significantly corre-lated with IQ, the varying degrees of correlationbetween IQ and the three adaptive domains bringsinto question the idea of a direct relationship,which is presumed in the ID diagnosis (i.e., ‘‘Tomeet diagnostic criteria for intellectual disability,the deficits in adaptive functioning must bedirectly related to the intellectual impairments…,’’American Psychiatric Association, 2013, p. 38).

Future conceptualizations of ID may benefitfrom further shifting the diagnostic emphasis todeficits in adaptive functioning, as this might betterdefine a subgroup of individuals who are highlyvulnerable to exploitation or injury and requireadditional protections (regardless of IQ). Barkleyand colleagues have proposed the concept ofadaptive disability, in which deficits in adaptivefunctioning are associated with behavioral factors(e.g., conduct problems, inattention, aggression)within the context of broadly intact intelligence(Barkley et al., 2002; Shelton et al., 1998). Otherrecent work has identified relatively distinctcognitive–behavioral clusters associated with defi-cits in adaptive functioning, with IQ representingonly one of many variables thought to contribute todeficits in adaptive functioning (Papazoglou, Ja-cobson, & Zabel, 2013a). We propose that futureDSM revisions consider the evidence for theconcept of an adaptive disability in which deficitsin adaptive functioning are the primary diagnosticfeature, with associated specifiers to qualify pre-sumed etiologies (e.g., with intellectual deficits,with executive functioning deficits, with affectivedysregulation, etc.).


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In closing, we strongly recommend thatdiscussion concerning the impact of new DSM-5ID diagnostic criteria include discussion of practicalassessment issues that may occur when newdiagnostic criteria are implemented using existingtest instruments such as the ABAS-II. First,although existing adaptive skill instruments havebeen shown to be reliable, it is very important thatthe underlying construction of the tests be consid-ered when they are applied to new diagnosticformulations. As noted earlier, the domain factorstructure of the ABAS-II was organized on the basisof theoretical foundations, and the model thenunderwent confirmatory factor analysis. Althoughthis is an appropriate method for test construction,it may not capture the strongest factor loadings orprovide information about other potential arrange-ments of the scales. Subsequently, individualadaptive skill area deficits may be somewhat‘‘silenced’’ in the larger factor model. As such, thediagnostic utility of existing adaptive skill instru-ments such as ABAS-II should be explored beforepresuming that they are equally valid under bothDSM-IV-TR and DSM-5 conditions, and clinicaljudgment should continue to be emphasized in thediagnostic process to help minimize possiblepsychometric measurement issues. Moreover, agree-ment between different measures should be ex-plored, as quantification of deficits in adaptivefunctioning can vary considerably between instru-ments (Papazoglou, Jacobson, & Zabel, 2013b) andfurther complicate the diagnostic picture. Tomitigate the potential impact of these issues,DSM-5 recommends that the clinician use multiplesources of information as well as clinical judgmentwhen establishing whether an individual presentswith significant deficits in adaptive behavior.

In addition, we recommend that the appropri-ateness of content from current adaptive skillinstruments be reviewed, particularly given therenewed emphasis placed on adaptive impairmentin the DSM-5 ID diagnostic formulation. Due to thepace of accommodative technology, the definition ofan adaptive deficit is likely to continue to changerapidly. Although the advent of GPS guidancesystems, text-to-speech software, smart phones,electronic cueing devices, and other technologieshas created exciting new habilitation opportunities,the speed with which these devices become availableoutpaces the more time-intensive process necessaryfor the development and standardization of adaptiveskill measures. This dilemma will likely continue,

creating a disparity between the reality of theindividual’s situation (e.g., ability to use a smartphone and access the Internet) and the content ofthe latest version of a standardized adaptive skillinstrument (e.g., ability to use a pay phone and reada newspaper). Lack of items reflecting an individual’sability to use technologies such as a smart phone, acomputer, and the Internet creates both face validityand content validity questions, particularly as thesetypes of technologies continue to become normal,necessary components of daily living rather thanaccommodative technologies or interventions. Thisis a particularly salient dilemma for the ABAS-II,which contains the same item content from theoriginal ABAS, which was developed prior to thecollection of standardization data between Decem-ber 1998 and December 1999.

Although these findings have important im-plications for clinical practice and policy, this studyhas several limitations. All children were clinicallyreferred, so results may not be consistent withpotential findings in a nonreferred population,although it is worth noting that the decision-making process regarding classification of ID isinherently a clinical one. More specifically, how-ever, the Kennedy Krieger Institute is an interna-tionally recognized center of excellence for childrenwith developmental disabilities, thus the populationof children referred for evaluation here may be moresignificantly impaired than those for whom IDclassification decisions are made in other settings(e.g., local school special education decisions). If thisis indeed the case, the measurement issues raisedconcerning the ABAS-II skill area and adaptivedomain scores may be overrepresented or underrep-resented. More research is needed regarding thefactor structure of the ABAS-II and whether the 9and 10 skill areas and three domains representappropriate factor groupings of the ABAS-II items.Research to date has shown only modest support forthe three domains (Wei et al., 2008), and there arelimited data on the 9-and-10 factor solutions. Nodata were available regarding whether cliniciansactually made a diagnosis of ID for all 166 childrenwho met formal DSM-IV-TR criteria, and, to ourknowledge, there are no published data examininghow consistently clinicians adhered to DSM-IV-TRdiagnostic criteria when making a diagnosis of ID.Nevertheless, these findings suggest a risk of fewer IDdiagnoses when existing adaptive functioning in-struments are used as the primary means by which toimplement DSM-5 criteria for adaptive impairment.


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Received 7/6/2013, accepted 10/2/2013.

Authors:Aimilia Papazoglou, Children’s Healthcare ofAtlanta; Lisa A. Jacobson, Kennedy KriegerInstitute; Marie McCabe, Saratoga Springs, NY;Walter Kaufmann, Boston Children’s Hospital;T. Andrew Zabel, Kennedy Krieger Institute.

Correspondence concerning this article should beaddressed to Aimilia Papazoglou, Children’s Health-care of Atlanta, Neuropsychology, Suite 180, 5455Meridian Mark Road, Atlanta, GA 30342 (e-mail:[email protected]).


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DOI: 10.1352/1934-9556-52.3.165


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