The continuous performance test, identical pairs: norms, reliability and performance in healthy controls and patients with schizophrenia in Singapore.

AIM

To provide normative values for the healthy ethnic Chinese Singaporean population and a large sample of patients with schizophrenia for the Continuous Performance Task-Identical Pairs (CPT-IP). Participants Data were collected on 1011 healthy ethnic Chinese and 654 patients diagnosed with schizophrenia, all between 21 and 55 years of age.

METHODS

Data were stratified by age and gender. The effects of age, gender and education were explored in patients and controls. Performance indices were assessed in their ability to predict group inclusion. Controls' performance was compared with that reported in a US sample.

RESULTS

Performance was affected by age, sex, and education, with youth, male sex and higher education providing a performance advantage. Patients' performance was lower than controls' by more than 1 standard deviation, with the 3-digit d' score most significantly discriminating between controls and patients. The effects of socio-demographic factors on performance were in line with those conducted in the US and previously reported in the literature.

CONCLUSIONS

This is the largest norming study ever conducted on the CPT-IP. It will enable investigators and clinicians to select appropriate indices to assess severity of cognitive decline and/or evaluate cognitive remediation therapy outcomes after taking into account age, gender and education factors.