Assessment of the accuracy of regression equations proposed for estimating premorbid intellectual functioning on the Wechsler Adult Intelligence Scale

Estimating premorbid intelligence in people living with dementia: a systematic review

OBJECTIVES

In diagnosing dementia, estimating premorbid functioning is critical for accurate detection of the presence and severity of cognitive decline. However, which assessments of premorbid intelligence are most suitable for use in clinical practice is not well established. Here, we systematically evaluate the validity of instruments for measuring premorbid intelligence in people living with dementia.

DESIGN AND SETTING

In this systematic review, electronic databases (EMBASE, PsycINFO, MEDLINE, CINAHL, and AMED) were searched to identify studies reporting on objective measures of premorbid intelligence in dementia. Participants from included studies were recruited from local communities and clinical settings.

PARTICIPANTS

A total of 1082 patients with dementia and 2587 healthy controls were included in the review.

MEASUREMENTS

The literature search resulted in 13 eligible studies describing 19 different instruments. The majority of instruments (n = 14) consisted of language-based measures, with versions of the National Adult Reading Test (NART) being most commonly investigated.

RESULTS

Preliminary evidence suggested comparable performance of patients with mild dementia and healthy controls on word reading tasks in English, Portuguese, Swedish, and Japanese. In moderate dementia, however, the performance was significantly impaired on most verbal tasks. There was a lack of reliability and validity testing of available instruments, with only one of the included studies reporting psychometric properties within the patient group.

CONCLUSIONS

The results demonstrate that there is a wide range of tools available for estimating premorbid intelligence in dementia, with cautious support for the potential of word reading tasks across different languages in individuals with mild dementia. However, the review highlights the urgent need for extensive assessments of the psychometric properties of these tasks in dementia. We propose that further longitudinal research and assessments of nonverbal measures are necessary to validate these instruments and enhance diagnostic procedures for people living with dementia worldwide.

Comparison of measured and estimated cognitive ability in older adolescents with and without ADHD

Premorbid intellectual function estimation is a crucial part of patient evaluation following a traumatic brain injury (TBI), especially in individuals with ADHD who are at higher risk for TBI compared to their non-ADHD peers. This study investigates the value of using regression-based estimates of intelligence for concurrently predicting measured intelligence in a sample of older adolescents with and without a childhood history of ADHD. Correlations between measured and estimated intelligence are highly significant in the full sample and in the individual groups. Adding reading performance to the regression equation increases the accounted-for variance in both groups. Results indicate that regression equations based on demographic characteristics constitute a valid method for estimating premorbid functioning in adolescents with ADHD and that they can play an essential role in the assessment of individuals with ADHD who sustain TBI, especially when measures of word reading are used to augment demographic estimates.

Communication abilities of individuals with late-stage Alzheimer disease

The communication abilities of 49 individuals in the late stage of Alzheimer disease were examined in relation to other markers of late-stage Alzheimer disease (e.g., incontinence and ambulatory ability). Two existing tools used to stage severity of dementia, the Global Deterioration Scale and the Functional Assessment Stages, have represented communication abilities in individuals with late-stage Alzheimer disease to be minimal to nonexistent. The individuals in this sample showed greater communication skills and verbal output than would be predicted by these scales.

Postdicting verbal IQ of elderly individuals

We undertook a longitudinal crossvalidation of the Ryan and Paolo (1992) equation's ability to postdict Wechsler Adult Intelligence Scale-Revised (WAIS-R) Verbal IQ (VIQ) from National Adult Reading Test (NART) performance measured 5 years after VIQ scores were obtained, for a sample of 49 elderly normal individuals (mean age 71 years). Five-year interval postdiction accuracy agreed very well with the results of the original, concurrent study. Clinical utility is still limited, however, as VIQ must decline by 16.3 points for 95%-detection sensitivity. A new regression equation that utilizes a combination of NART errors and WAIS-R Vocabulary age-scaled scores (measured 3 years earlier) provided slightly better expected clinical sensitivity and accounted for 49% of the variance in VIQ scores.

Prognostic indicators in medical rehabilitation of traumatic brain injury: a commentary and review

The National Information System (NIS) project is developing consensus opinion regarding a proposed structural framework for the prognostic data to be collected as part of this proposed multicenter research effort on severe traumatic brain injury (TBI). This article provide a brief history of the process, examines challenges facing rehabilitation research in this particular area, discusses reasons for identifying prognostic data within the research context of the NIS project, and describes methodologies for use of mathematical models in predicting outcome from TBI. The literature regarding prognostic parameters in severe TBI is briefly reviewed, utilizing three broad parameter categorizations: preinjury, injury, and postinjury. The implications of this research and directions for further study within the NIS project are discussed.

Prediction of recovery from traumatic brain injury

This paper encompasses the prediction of early and late recovery from traumatic brain injury (TBI). Predictors of the duration of coma and the utilization of posttraumatic amnesia duration to predict residual memory function are discussed. The issues surrounding prediction of long-term neurobehavioral recovery from TBI are considered, particularly the patient and clinical variables that are related to intellectual recovery. Findings from the NIH Traumatic Coma Data are reviewed pertaining to testability as a criterion for outcome. In addition to discussing the relationship of specific neurologic indices of TBI as predictors, the results obtained using a regression model are summarized. Finally, the relationship of neuroimaging findings to neurobehavioral outcome is discussed including directions for future research.

A comparison of indices of premorbid intelligence in clinical populations

Estimation of premorbid intelligence using the regression formula developed by Barona et al. (1984) was compared with prorated IQ's based on the higher of the Vocabulary or Picture Completion subtests from the WAIS-R. Actual and predicted premorbid IQ's of 50 brain-damaged patients were compared to those of 35 non-brain-damaged patient controls equated on age and education. For both groups, the Barona et al. (1984) formula produced mean IQ's close to 100, though greatly restricted the range. The prorated IQ's tended to be over-estimated in the patient control group, but not the brain-damaged group. Compared with the regression based formula, the distribution of these prorated IQ's was more consistent with the WAIS-R standardization sample.

IQ: R.I.P

In the early decades of this century, "IQ," as score and concept, not only satisfied psychology's need for metrical respectability, but it caught the public's fancy and rapidly became a household word. Reified in many popular tests, it has withstood onslaughts from factor analysis, from concerned social scientists, from judicial fiat, and from scientific knowledge about mental abilities, brain functions, and neuropathology. In neuropsychological practice its use--and that of any scores representing sums or averages of disparate data obtained from tests of brain functions and mental abilities--can obscure specific facets of a subject's neuropsychological status or misrepresent it generally. This 70-year-old concept has outlived its usefulness. Neuropsychology needs to seek more appropriate alternatives to the IQ for describing and conceptualizing mental functioning.

Effects of lateralized cerebral dysfunction on the Continuous Paired-Associate Test

Some authorities have advocated matching tests on several critical psychometric properties before inferring the presence of a differential pattern of deficit. This study examined the effects of lateralized cerebral dysfunction on the matched Verbal and Design subtests of the Continuous Paired-Associate Test (CPAT). Patients with lateralized destructive lesions were studied in Experiment 1. Epileptic patients with lateralized electroencephalographic findings were studied in Experiment 2. Left but not right hemispheric abnormalities impaired performance on the Verbal CPAT, but only for destructive lesions. The Designs CPAT was a nonspecific indicator of cerebral dysfunction. For studies with the goal of predicting laterality of cerebral dysfunction, we advocate a two-step strategy of test development. The first step would make use of the principle of double dissociation in selecting items to compose subtests. The second step would involve an item analysis of subtests to determine the need for matching.