WAIS-IV Seven-Subtest Short Form: Validity and Clinical Use in Schizophrenia

OBJECTIVE

This study assesses the psychometric properties of Ward's seven-subtest short form (SF) for WAIS-IV in a sample of adults with schizophrenia (SZ) and schizoaffective disorder.

METHOD

Seventy patients diagnosed with schizophrenia or schizoaffective disorder were administered the full version of the WAIS-IV. Four different versions of the Ward's SF were then calculated. The subtests used were: Similarities, Digit Span, Arithmetic, Information, Coding, Picture Completion, and Block Design (BD version) or Matrix Reasoning (MR version). Prorated and regression-based formulae were assessed for each version.

RESULTS

The actual and estimated factorial indexes reflected the typical pattern observed in schizophrenia. The four SFs correlated significantly with their full-version counterparts, but the Perceptual Reasoning Index (PRI) correlated below the acceptance threshold for all four versions. The regression-derived estimates showed larger differences compared to the full form. The four forms revealed comparable but generally low clinical category agreement rates for factor indexes. All SFs showed an acceptable reliability, but they were not correlated with clinical outcomes.

CONCLUSIONS

The WAIS-IV SF offers a good estimate of WAIS-IV intelligence quotient, which is consistent with previous results. Although the overall scores are comparable between the four versions, the prorated forms provided a better estimation of almost all indexes. MR can be used as an alternative for BD without substantially changing the psychometric properties of the SF. However, we recommend a cautious use of these abbreviated forms when it is necessary to estimate the factor index scores, especially PRI, and Processing Speed Index.

Application of the Seven-Subtest Short Form of the WAIS-R in African Americans with Brain Damage

This study examined the accuracy of Ward's (1990) seven-subtest short form for predicting WAIS-R IQs of 54 African Americans with brain damage. Means for age, education, and FSIQ were 47.1 years (SO= 16.6), 10.8 years (SD= 2.4), and 79.3 (SD = 11.6). Short-form VIQs, PIQs, and FSIQs were within ±1 standard error of measurement of the actual WAIS-R scores 81.5%, 83.3%, and 83.3% of the time. This abbreviation may be applied to African Americans with brain damage when general estimates of intellectual functioning are required. However, the shortened scale detected reliable VIQ.PIQ discrepancies on the WAIS-R only 53% of the time. Therefore, interpretation of significant short-form-based VIQ-PIQ discrepancies should be avoided.

Two Types of Tables for Use with the Seven-Subtest Short Forms of the WAIS-III

Now that the WAIS-R has been superseded by the WAIS-III, clinicians will incorporate the revision into their practices and, as in the past, administer the Ward (1990) seven-subtest short from to reduce administration time. Therefore, differences between Verbal and Performance IQ estimates required at the 95% and 99% levels of significance are reported for the Ward seven-subtest short form and a new seven-subtest short form that substitutes Matrix Reasoning for Block Design. Also provided are precision ranges for the estimated Verbal, Performance, and Full Scale IQs from the two short forms at the 85%, 90%, 95%, and 99% levels of confidence. IQ differences and precision ranges are given for each of the 13 age groups and the average across age groups in the standardization sample.

Two Types of Tables for Use with the Seven-Subtest Short Form of the WAIS-R

Differences between Verbal and Performance IQ estimates required at the 95% and 99% levels of significance are reported for the Ward (1990) seven-subtest short form of the Wechsler Adult Intelligence Scale-Revised (WAIS-R). Precision ranges are also provided for the Verbal, Performance, and Full Scale IQs at the same levels of confidence. IQ differences and precision ranges are given for each of the nine age groups in the standardization sample as is the average for the entire group. All calculations are based on the standard errors of measurement for the short form reported by Axelrod, Woodard, Schretlen, and Benedict (1996).

Prorating IQ Scores for Older Adults: Validation of a Seven-Subtest WAIS-R with the Mayo Older Americans Normative Sample

Concurrent validity of a seven-subtest short form (7SF) of the revised edition of the Wechsler Adult Intelligence Scale (WAIS-R) was examined in 733 cognitively normal adults between 56 and 99 years of age who participated in Mayo's Older Americans Normative Studies (MOANS). Pearson correlation coefficients between actual and prorated MAYO Verbal, Performance, and Full Scale IQ scores ranged from r =. 93 to r =. 97. Actual and prorated FSIQ scores differed by 6 points or less for 98% of participants, and the observed deviations did not vary as a function of age. These results support the use of this WAIS-R short form to prorate MAYO IQ scores for older adults.

How well does IQ predict neuropsychological test performance in normal adults?

The strength and nature of the association between IQ and performance on other cognitive tests has both practical and conceptual significance for clinical neuropsychology. In this study, 28 measures derived from 16 cognitive tests were analyzed as a function of IQ in 221 adults. Participants were grouped by their IQ scores as having below average (BA), average (A), or above average (AA) intelligence. Planned comparisons revealed that A adults performed significantly better than BA adults on 25 of the 28 cognitive measures, and that AA adults performed significantly better than A adults on 19 of 28 measures. Effect sizes averaged.74 for BA-A comparisons and.41 for A-AA comparisons. Linear, quadratic, and cubic functions described the relationships between IQ and cognitive test performance equally well for most individual test measures and for a composite index of test performance, whereas quadratic and cubic functions explained the proportion of abnormal performances better than a linear function. These findings confirm that IQ predicts concurrent neuropsychological performance across the entire spectrum of intelligence, but more so among persons of average IQ or less than among those with above average IQ.

Evaluation of two brief and reliable estimates of the WAIS-R

Performance of 200 mixed neuropsychiatric patients on the WAIS-R were compared to the summary scores for Kaufman's Brief Intelligence Test (K-BIT) and a seven subtest short form of the WAIS-R. Correlations between verbal, non-verbal, and composite of the full WAIS-R with the K-BIT were significantly lower than the correlations with the WAIS-R shore form. The percentage of cases on the short forms that fell within 5 points of the full WAIS-R was higher for the seven subtest version of the WAIS-R than the K-BIT. Specifically, Verbal, Nonverbal/Performance, and Composite/Full Scale scores on the WAIS-R short form feel within 5 points for 89%, 74%, and 92% of the cases while on the K-BIT only 52%, 40%, and 50% fell within 5 points.

Utility of the seven subtest WAIS-R short form in a female sample with brain damage

We examined the accuracy of the WAIS-R seven subtest short form (Ward, 1990) for predicting IQs of 130 females with brain damage or dysfunction. Means for age, education, and FSIQ were 44.37 years (SD = 18.46), 12.74 years (SD = 2.42), and 87.64 (SD = 13.62). Results indicated that 93%, 84%, and 93% of short form estimated VIQs, PIQs, and FSIQs were within +/-5 points of their actual WAIS-R scores. In terms of Wechsler's (1981) seven category intelligence classification, levels of agreement were 83%, 72%, and 82% for the Verbal, Performance, and Full scales, respectively. These findings support the use of the seven subtest short form with brain-damaged women when time is at a premium and only a general estimate of intellectual functioning is required.