Applying the British picture vocabulary scale to estimate premorbid cognitive ability in adults.

Estimating premorbid cognitive ability is an essential part of assessment as well as being an important consideration in research. The most widely used approach to premorbid assessment, The National Adult Reading Test (NART), relies on word reading ability. However, this can be problematic in patients where communication is impaired. This research assessed the effectiveness of a receptive vocabulary test, the British Picture Vocabulary Scale II (BPVS) as an alternative. Correlations were found between the BPVS, NART and the Weschler Abbreviated Scale of Intelligence (WASI) in 87 healthy participants. Regression equations were calculated relating NART and BPVS raw scores to IQ scores in the healthy sample. WASI, NART and BPVS scores were also obtained in 19 patients with varying neurological etiology as part of their routine assessment. Results showed that 18 out of 19 patients obtained BPVS derived IQ scores similar to or higher than their WASI IQ. Whereas mean BPVS derived IQ did not differ significantly between the standardization and clinical samples, WASI IQ scores were lower in the patient group. The findings suggest that the BPVS II 'holds' after acquired cognitive impairment and is a promising alternative method for estimating premorbid IQ in patients who have difficulties reading or verbalizing.