A comparison of three measures of estimating premorbid intellectual level in dementia of the Alzheimer type

Estimation of premorbid intellectual function is becoming increasingly recognized as a crucial component of neuropsychological assessment in both research and clinical practice. Estimation based on accuracy of pronunciation of irregular words via the National Adult Reading Test (NART) has become popular. However, alternative methods have recently been developed, including the Cambridge Contextual Reading Test (CCRT) and the Spot-the-Word Test (STW). In the present study, the three methods were compared in 21 elderly patients with dementia of the Alzheimer type (DAT), relative to a large sample of healthy controls. Performance on all three measures was relatively unaffected by DAT, and in the controls, both the NART and the CCRT correlated relatively well with current verbal intelligence. However, the correlation between the STW and current verbal intelligence was disappointingly low. The DAT subjects showed a significantly greater improvement in performance (relative to controls) when the irregular words were placed in context (meaningful sentences). The results suggest that the CCRT may provide the fairest estimate of premorbid verbal intelligence in DAT.Copyright © 1998 John Wiley & Sons, Ltd.     

The Assessment of premorbid ability: A critical review

Abstract

Estimating premorbid intelligence level has become an established and central component of neuropsychological research and practice. Three main approaches are currently employed, estimate based on demographic variables, reading ability, or lexical decision-making. Each have relative strengths and weaknesses. Demographic-based regression equations have the advantage that the estimate is completely independent of the subject's current cognitive state, but such approaches only predict ～50% of the variance in measured intelligence. Also, in neurodevelopmental conditions, maximum educational and occupational attainment may be compromised by the disease process. For use in the individual case, the margin of error may also be unacceptably large. Estimates based on oral pronunciation of irregular words, typified by the National Adult Reading Test (NART), have become the most popular method. Pronunciation accuracy correlates highly with measured intelligence, and is relatively resistant to the effects of a wide range of clinical disorders. Combining demographic variables with NART scores appears to significantly increase the percentage of variance in measured intelligence compared with either demographics or NART alone. Unfortunately a snowball has started rolling, where the NART is now used almost routinely in clinical research and practice. Closer inspection reveals that NART performance may be compromised in a number of conditions including moderate to severe Alzheimer's disease, chronic schizophrenia, Korsakoff's syndrome, Huntington's disease and cranial irradiated glioma patients. It is essential that the insensitivity of the NART to the clinical condition under investigation is demonstrated prior to its routine use as a premorbid measure. Placing the NART words in context (i.e. within meaningful sentences) may provide a more accurate estimate of premorbid function. The final approach involves lexical decision-making, where subjects are presented with two items and are required to state which of the pair is a real word. This approach overcomes some of the problems associated with the pronunciation based tests, i.e. it can be used with patients with dyslexia or articulatory problems, and may provide a more valid estimate of premorbid ability in self-educated individuals who may be familiar with the word and its meaning, but be unsure regarding pronunciation. Spot-The-Word performance correlates highly with verbal intelligence, and in elderly patients with suspected cognitive decline, Spot-The-Word performance appears to be unaffected. However, further evidence is required regarding the relative insensitivity of Spot-The-Word to confirmed clinical conditions such as Alzheimer's disease.     

Neuropsychologic impairment in astrocytoma survivors

Thirteen patients selected for long-term survival with primary astrocytic tumor (who failed to return to premorbid educational or vocational levels) were examined by neuropsychologic tests of specific and generalized higher cortical functions. In the absence of tumor regrowth or other neurologic disorders, each demonstrated difficulty in problem solving or coping with novel situations when previously acquired abilities, overlearned material, and psychometric intelligence appeared consistent with their premorbid level. The diffuse difficulties were unrelated to tumor type or location, and were not explicable by existing focal deficits, psychotic or depressive thought disorders, metabolic difficulties, or hydrocephalus. These examinations explained in part why these patients failed to resume active social lives or premorbid employment. The diffuse cortical dysfunction was most notable on the Category Test, Trails B, and Localization component of the Tactual Performance Test.     

Intellectual functioning in adolescents with indicators of psychosis: evidence for decline in functioning related to number of psychotic features?

Substantial research has demonstrated that adults with schizophrenia display intellectual decline compared to their premorbid levels of functioning. Research of this type, however, is not as common in adolescents with psychotic disorders. Since many first-episode adolescents with psychotic disorders other than schizophrenia may eventually meet criteria for this diagnosis, we examined first admission adolescents with variable psychiatric diagnoses. In this study, current intellectual functioning was compared to estimated premorbid functioning (estimated with word recognition reading), and the difference between these scores was related to the number of indicators of psychosis that was present in each case. Subjects consisted of 513 inpatients, ranging in age from 13 to 17 years, who were admitted to the adolescent service of a private psychiatric hospital. Indicators of psychosis came from clinical diagnoses, self-report measures, and clinical rating scales. Across the entire sample of 513 subjects the greater the number of indicators of psychosis that was present, the greater the estimated premorbid/current intelligence quotient (IQ) discrepancy. Type of IQ test, differences in intellectual premorbid functioning, demographic variables, and type of treatment were all unassociated with risk for IQ discrepancy. Within the limitations of estimation of premorbid intellectual functioning, these data suggest that intellectual decline is present at the time of the first psychiatric admission in psychotic adolescent patients who do not necessarily meet diagnostic criteria for schizophrenia and that this discrepancy is greater in patients with more indicators of psychosis.     

Development and validation of a model for estimating premorbid verbal intelligence in the elderly.

In a preliminary effort to improve the early diagnosis of dementia, we developed a regression-based method for estimating premorbid intelligence measured by the ability to read irregular words from the American version of the Nelson Adult Reading Test (AMNART). Using errors on the AMNART and years of education, a model for predicting current verbal intelligence (VIQ) was developed in a sample of nondemented elderly. Double cross validation showed that the model had high accuracy and stability in estimating current VIQ in nondemented subjects. The model was then used to estimate premorbid VIQ in mildly demented subjects. Estimated premorbid IQ exceeded current IQ by at least 10 points and did not differ from that of nondemented subjects. Less than 10% of nondemented elderly had discrepancies that were as large. If intellectual decline predicts future functional loss and can be reliably measured using cross-sectional data, the requirement of functional impairment may be an unnecessary barrier to the early diagnosis of dementia.     

A critical note on Lezak's ‘Best performance method’ in clinical neuropsychology

Abstract

A fundamental problem in clinical neuropsychology is the estimation of premorbid levels of cognitive functioning. Lezak (1983) described the so-called ‘best performance method’ of estimating premorbid abilities. Essentially, this method consists in using the highest test scores or the best performance in everyday tasks as the best estimate of premorbid ability. This paper describes three studies of the empirical consequences of using the ‘best performance method’: The first study demonstrates that application of this method on WAIS subtests leads to a gross overestimation of intelligence as measured by the IQ. The second study corroborates this finding and also shows that overestimation of intelligence leads to systematic errors in the expected performance in neuropsychological tests in normal subjects. Finally, the third study shows that this is also the case in patients with diffuse cerebral atrophy.     

Clinical Characteristics and Treatment Outcomes of De Novo Nonconvulsive Status Epilepticus: A Retrospective Study

Background and PurposeNonconvulsive status epilepticus (NCSE) is challenging to diagnose. This study aimed to describe and classify the clinical features and electroencephalography (EEG) findings of patients with de novo NCSE and to correlate them with clinical outcomes.MethodsWe retrospectively reviewed the medical and EEG records of patients admitted to our institution with altered mentation and EEG abnormalities from January 1, 2013 to December 31, 2018. We evaluated premorbid modified Rankin Scale (mRS) scores, underlying disorders, precipitating factors, clinical manifestations, laboratory tests, and outcomes after a 3-month follow-up. Patients who met the Salzburg Consensus Criteria for NCSE were categorized into good-outcome and poor-outcome groups. A good outcome was defined as 1) clinical and electrographic seizures ceasing after treatment, and 2) an mRS score of ≤2 or remaining unchanged during the 3-month follow-up. A poor outcome was defined as 1) death, 2) seizures continuing despite treatment, or 3) a follow-up mRS score of ≥3 in a patient with a premorbid mRS score of ≤2, or a follow-up mRS score that increased in a patient with a premorbid mRS score of ≥3.ResultsThe 48 included patients comprised 37 categorized into the good-outcome group and 11 into the poor-outcome group. The presence of acute metabolic disturbances was significantly correlated with poor outcome (p=0.036), while the other analyzed variables were not significantly correlated with outcomes.ConclusionsAcute metabolic disturbances in NCSE are associated with poor outcomes. Adequate treatment of underlying reversible disorders alongside controlling seizures is critical for patients with NCSE.     

Association between duration of untreated psychosis, premorbid functioning, and cognitive performance and the outcome of first-episode schizophrenia in Japanese patients: prospective study

OBJECTIVE: The aim of the present study was to identify the relationship between duration of untreated psychosis (DUP), premorbid functioning, and cognitive dysfunction and the outcome of first-episode schizophrenia. METHOD: Thirty-four neuroleptic-na?ve patients who consulted hospitals in Tokyo and who were treated by psychiatrists for the first time were evaluated with regard to DUP, premorbid functioning, psychiatric symptoms, and global functioning. The neuropsychological test battery consisted of the Letter Cancellation Test, Trail-Making Test, Digit Span and Verbal Fluency Test. One year later, 24 of the subjects were reassessed for psychiatric symptoms, global functioning, and social functioning, and the relationships between DUP, premorbid functioning, and cognitive performance and the outcome was investigated. RESULTS: Short DUP, good premorbid functioning, and good Letter Cancellation Test, Digit Span and Verbal Fluency Test scores were significantly associated with good outcome. CONCLUSIONS: The present results in a Japanese sample are consistent with previous international evidence that delay of initial treatment, premorbid functioning, and cognitive deficits are associated with outcome. A major limitation of the present study was the small size of the subject group. But because the subjects were relatively homogeneous and not influenced by psychoactive substances, the results reflect the essence of the disorder.     

A critical note on Lezak's 'best performance method' in clinical neuropsychology

A fundamental problem in clinical neuropsychology is the estimation of premorbid levels of cognitive functioning. Lezak (1983) described the so-called 'best performance method' of estimating premorbid abilities. Essentially, this method consists in using the highest test scores or the best performance in everyday tasks as the best estimate of premorbid ability. This paper describes three studies of the empirical consequences of using the 'best performance method': The first study demonstrates that application of this method on WAIS subtests leads to a gross overestimation of intelligence as measured by the IQ. The second study corroborates this finding and also shows that overestimation of intelligence leads to systematic errors in the expected performance in neuropsychological tests in normal subjects. Finally, the third study shows that this is also the case in patients with diffuse cerebral atrophy.     

The National Adult Reading Test as a measure of premorbid intelligence: a comparison with estimates derived from demographic variables.

Since its publication in 1982, the National Adult Reading Test (NART; Revised Version, NART-R) has become a widely accepted method for estimating premorbid levels of intelligence in neuropsychological research. However, the assumption that NART/NART-R performance is relatively independent of brain damage has been increasingly challenged in recent years. In a number of conditions, including Alzheimer dementia and Korsakoff's syndrome, studies have indicated a deterioration in reading ability, leading to an underestimated premorbid IQ. In a reaction to these studies, some researchers have advocated the use of demographic variables as a more suitable foundation for accurately predicting premorbid intelligence. We addressed this issue by calculating IQ estimates on the basis of NART/NART-R, demographic variables, and a combination of the two approaches and by comparing these with current WAIS/WAIS-R IQ in patients with Korsakoff's syndrome, Alzheimer dementia, frontal or temporal lobe lesions, and in healthy controls. Estimated premorbid IQs did not differ across groups, whether derived from NART/NART-R or demographic variables. Those based on NART/NART-R demonstrated higher correlations with current WAIS/WAIS-R IQ in controls and patients than those derived from demographic variables. An equation combining NART scores with demographic variables did not significantly increase the amount of variance in IQ explained by NART only, either in patients or controls. The data offer reassurance regarding the continued use of NART as a valid estimate of premorbid intelligence in a number of conditions.     

Estimating verbal intelligence in unipolar depression: Comparison of word definition and word recognition

Depression is known to be associated with deficits in effortful processing and word fluency. Automatic processes, instead, appear largely intact in depressed patients. It was investigated whether active word definition could be a less appropriate method than passive word recognition as a measure of verbal intelligence in depression. The valid assessment of premorbid IQ is important for correct comparison with current cognitive efficiency of depressed individuals, since premorbid IQ serves as baseline or control parameter to estimate the extent and severity of acquired cognitive impairments, both in the clinical and the research context. Two vocabulary tests were administered to 90 patients (31 women) with unipolar depression and 30 control subjects (15 women): a word definition task [the vocabulary subtest of the Wechsler Adult Intelligence Scale (WAIS-R)] and a word recognition task [the Multiple choice vocabulary test (MWT)]. In the depressed sample, scores of the MWT tended to be higher than WAIS-R scores. For depressed women, the MWT score was significantly higher than the WAIS-R score. In the control sample, no differences between MWT and WAIS-R scores were observed. Our findings indicate that word definition tasks could underestimate verbal intelligence especially in depressed women. For depressed women, it could be more appropriate to administer word recognition than word definition as an estimate of premorbid or verbal intelligence.     

Mood and cognition in leucine‐rich repeat kinase 2 G2019S Parkinson's disease

The behavioral and cognitive features of the leucine‐rich repeat kinase G2019S mutation in Parkinson's disease in the Ashkenazi Jewish population are not well described; therefore, we sought to more systematically characterize these features using a semistructured psychiatric interview and neuropsychological testing. Twenty‐one Ashkenazi Jewish patients having the leucine‐rich repeat kinase G2019S mutation were compared with age‐ and sex‐matched Ashkenazi Jewish patients with Parkinson's disease without mutations. Although overall rates of affective disorders were not greater in mutation carriers, the carriers exhibited a 6‐fold increased risk of premorbid affective disorders (odds ratio, 6.0; P = .10), as determined by the Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders–IV. Of interest, we identified 2 leucine‐rich repeat kinase carriers with bipolar disorder; no mutation‐negative subjects had this diagnosis. Performance on the Hopkins Verbal Learning Test–Revised, Judgment of Line Orientation, and Frontal Assessment Battery was consistent with previous reports and did not differ between groups. Study findings suggest a possible association between premorbid mood disorders and leucine‐rich repeat kinase Parkinson's disease, warranting further evaluation. © 2011 Movement Disorder Society     

Estimating verbal intelligence in unipolar depression: comparison of word definition and word recognition

Depression is known to be associated with deficits in effortful processing and word fluency. Automatic processes, instead, appear largely intact in depressed patients. It was investigated whether active word definition could be a less appropriate method than passive word recognition as a measure of verbal intelligence in depression. The valid assessment of premorbid IQ is important for correct comparison with current cognitive efficiency of depressed individuals, since premorbid IQ serves as baseline or control parameter to estimate the extent and severity of acquired cognitive impairments, both in the clinical and the research context. Two vocabulary tests were administered to 90 patients (31 women) with unipolar depression and 30 control subjects (15 women): a word definition task [the vocabulary subtest of the Wechsler Adult Intelligence Scale (WAIS-R)] and a word recognition task [the Multiple choice vocabulary test (MWT)]. In the depressed sample, scores of the MWT tended to be higher than WAIS-R scores. For depressed women, the MWT score was significantly higher than the WAIS-R score. In the control sample, no differences between MWT and WAIS-R scores were observed. Our findings indicate that word definition tasks could underestimate verbal intelligence especially in depressed women. For depressed women, it could be more appropriate to administer word recognition than word definition as an estimate of premorbid or verbal intelligence.     

Premorbid abnormalities in mania,schizomania, acute schizophrenia and chronic schizophrenia

The aim of this study was to examine the hypothesis that differences in outcome among affective and non-affective psychoses are associated with differences in the degree of developmental deviance. We conducted a retrospective survey of first contact cases treated over a 20-year period in a psychiatric hospital serving a catchment area in South London. All patients with non-depressive functional psychoses residing in the catchment area who received their first psychiatric treatment between 1965 and 1984 were included in the study. Cases were classified according to the relative chronicity of their illness into four non-overlapping groups: mania, schizomania, acute schizophrenia and chronic schizophrenia. There was a linear trend in the association between illness chronicity and proxy measures of developmental deviance, such as premorbid unemployment, single status and poor academic achievement. Compared to individuals with mania, schizophrenic patients had a 3–6 times increased risk of premorbid abnormality. For patients with schizomania and acute schizophrenia, the risk was 1.5–3 times greater than for manic subjects. We conclude that the prevalence of premorbid abnormalities is highest among chronic schizophrenia, but similar disturbances also occur, to a lesser degree, in less disabling affective and non-affective psychotic disorders.MRC Social Psychiatry Unit, Institute of Psychiatry     

Estimating premorbid general cognitive functioning for children and adolescents using the American Wechsler Intelligence Scale for Children-Fourth Edition: demographic and current performance approaches

Neuropsychologic evaluation requires current test performance be contrasted against a comparison standard to determine if change has occurred. An estimate of premorbid intelligence quotient (IQ) is often used as a comparison standard. The Wechsler Intelligence Scale for Children-Fourth Edition (WISC-IV) is a commonly used intelligence test. However, there is no method to estimate premorbid IQ for the WISC-IV, limiting the test's utility for neuropsychologic assessment. This study develops algorithms to estimate premorbid Full Scale IQ scores. Participants were the American WISC-IV standardization sample (N = 2172). The sample was randomly divided into 2 groups (development and validation). The development group was used to generate 12 algorithms. These algorithms were accurate predictors of WISC-IV Full Scale IQ scores in healthy children and adolescents. These algorithms hold promise as a method to predict premorbid IQ for patients with known or suspected neurologic dysfunction; however, clinical validation is required.     

Premorbid IQ as a predictor for the course of IQ in first onset patients with schizophrenia: a 10-year follow-up study

The aim of the present study was to examine the longitudinal course of IQ and its heterogeneity in patients with schizophrenia, from the perspective of the two main "subtypes" of schizophrenia described in the literature: progressive cognitive deficit versus cognitive stabilisation or recovery. Premorbid IQ scores and WAIS IQ scores of 100 first onset patients were obtained at first hospitalization (T1) and after 10 years (T2). Significant changes in IQ over time were found, representing (i) at T1, a deterioration compared to premorbid intelligence (B=-6.3, 95% CI -9.5 to -3.0, p<0.0001), followed by (ii) a recovery at T2 where IQ matched premorbid intelligence again (B=0.5, 95% CI -3.1 to 4.0, p=0.79). In addition, a significant interaction was found between course of IQ over time and estimated premorbid IQ, demonstrating that subjects with lower premorbid IQ levels remained stable over time whereas in individuals with higher premorbid IQ levels a pattern of deterioration was evident at T1, followed by a recovery up to premorbid level at T2. The data confirm the importance of estimated premorbid IQ as an indicator of the longitudinal course of cognitive functioning in patients with schizophrenia and add evidence to the hypothesis of heterogeneity or "subtypes" of schizophrenia. The data, however, do not confirm the existence of progressive deterioration of cognitive functioning. Rather, catching up of cognitive function later in the course of the illness may take place in those whose deficits become apparent in the early phases of illness, whereas those with the most severe premorbid impairments remain stable.     

Gender,premorbid characteristics and negative symptoms in schizophrenia

The interrelationships among gender, premorbid functioning, and negative symptoms were examined in a first-admission inpatient sample with DSM-III-R schizophrenia. Fifty-two subjects were assessed with the Schedule for the Assessment of Negative Symptoms (SANS) at baseline and 6-month follow-up. Three indicators of premorbid functioning were examined: the Premorbid Adjustment Scale, the Quick Test, and the GAF for the best month in the year prior to the baseline interview. Men and women had relatively similar ratings on each of the 5 SANS global subscales at both times; they were also relatively similar on most of the indicators of premorbid functioning. The men and women were categorized into low vs moderate-high negative symptom groups at baseline, and no differences in premorbid functioning were detected. When the sample was classified into those with and without consistent negative symptoms at baseline and 6-month follow-up, the enduring negative men and women had significantly poorer premorbid functioning in several areas than the consistently non-negative patients. Our findings support the importance of assessing negative symptoms longitudinally and suggest that gender is not strongly associated with negative symptoms and premorbid functioning in patients ascertained at early stages of schizophrenia.     

Index

Abstract

The American National Adult Reading Test (AMNART) was constructed to provide a valid and stable estimate of premorbid verbal IQ (VIQ) in dementing individuals. However, recent studies have brought into question its validity in patients with dementia of the Alzheimer type (DAT). The present study was designed to longitudinally assess the validity of the AMNART in 40 DAT patients and 40 demographically matched normal control (NC) subjects. The results showed that VIQ estimates for patients with DAT were significantly lower than those of NC subjects and declined significantly over time with increasing dementia severity as measured by the Mini-Mental State Examination (MMSE) and the Dementia Rating Scale (DRS). An MMSE-based correction factor was derived for the DAT group which allows for the effective estimation of premorbid VIQ in these patients.     

Neuropsychological dysfunction in antipsychotic-naive first-episode unipolar psychotic depression

OBJECTIVE: The profile of neuropsychological impairment associated with unipolar psychotic depression remains unclear. The authors used a neuropsychological test battery to characterize the neuropsychiatric profile of patients with unipolar psychotic depression, relative to that of patients with nonpsychotic unipolar depression, patients with schizophrenia, and healthy comparison subjects. METHOD: Study subjects included antipsychotic-naive patients with a first episode of psychotic unipolar depression (N=20), antipsychotic-naive and unmedicated patients with nonpsychotic unipolar depression (N=14), antipsychotic-naive patients with first-episode schizophrenia (N=86), and healthy volunteers (N=81). Groups were matched on age, sex, race, education, parental socioeconomic status, and estimated premorbid intelligence. Psychotic patients were followed clinically for 2 years to confirm diagnosis. All participants completed a standard neuropsychological battery, including tests of general intelligence, executive function, attention, verbal memory, motor skills, and visual-spatial perception. RESULTS: Patients with psychotic depression had a pattern of neuropsychological dysfunction that was similar to but less severe than that of patients with schizophrenia. In contrast, patients with nonpsychotic unipolar depression had a neuropsychological profile that was similar to that of healthy individuals but that included mild dysfunction on tests of attention. Neuropsychological test performance was generally independent of acute clinical symptoms, but some pairwise group differences were attenuated by covariation for symptom severity. CONCLUSIONS: The similar neuropsychological profiles for schizophrenia and psychotic depression suggest that these psychotic disorders may have common pathophysiological features. The dramatic differences in performance between the patients with psychotic depression and those with nonpsychotic depression point to a marked distinction in neurocognitive function associated with the expression of psychosis in depressed patients.     

Penetrating head injury in young adulthood exacerbates cognitive decline in later years

Few investigators have studied whether the behavioral effects of brain insult in adulthood are stable after the period of maximum recovery. We addressed this issue in a 30-year longitudinal study of 84 veterans of World War II, 57 with penetrating head injury (HI) and 27 with peripheral nerve injury (PNI), matched with respect to age, premorbid intelligence, and premorbid education. Each subject was examined during the 1950s and during the 1980s; each examination included the largely verbal Army General Classification Test (AGCT) (with Vocabulary, Arithmetic, and Block Counting subscales) and the Hidden Figures Test (which measures figure-ground discrimination). HI exacerbated decline in performance over time, irrespective of lesion site or cognitive test. HI and PNI subjects differed significantly (p less than 0.05) in AGCT Total and Arithmetic change scores, and means were in the same direction for all other measures. In analyses contrasting subjects in each of the eight lesion groups to PNI subjects, those with left parietal lobe injuries showed significantly greater decline from the 1950s to the 1980s on the Vocabulary and Arithmetic subscales of the AGCT, as did those with left temporal lobe injuries on the Arithmetic subscale, whereas subjects with right parietal lobe injuries showed significantly greater decline on the Hidden Figures Test. We hypothesize that the observed reduction of cognitive capacities late in life was due to some combination of HI in young adulthood, secondary effects of the injury occurring with time, effects of stress on remaining brain tissue caused by functioning for decades in a compromised state, and changes in the brain occurring with age. Although the HI subjects were not demented, follow-up studies must assess whether exacerbated decline is a harbinger of dementia.