Background: The 'double-diamond copy' task is a simple paper and pencil test part of the Bender-Gestalt Test and the Mini Mental State Examination (MMSE). Although it is a widely used test, its method of scoring is crude and its psychometric properties are not adequately known. The aim of the present study was to develop a sensitive and reliable method of administration and scoring.
Methods: The study sample included 93 normal control subjects (53 women and 40 men) aged 35.87 ± 12.62 and 127 patients suffering from schizophrenia (54 women and 73 men) aged 34.07 ± 9.83.
Results: The scoring method was based on the frequencies of responses of healthy controls and proved to be relatively reliable with Cronbach's α equal to 0.61, test-retest correlation coefficient equal to 0.41 and inter-rater reliability equal to 0.52. The factor analysis produced two indices and six subscales of the Standardised Copy of Pentagons Test (SCPT). The total score as well as most of the individual items and subscales distinguished between controls and patients. The discriminant function correctly classified 63.44% of controls and 75.59% of patients.
Discussion: The SCPT seems to be a satisfactory, reliable and valid instrument, which is easy to administer, suitable for use in non-organic psychiatric patients and demands minimal time. Further research is necessary to test its psychometric properties and its usefulness and applications as a neuropsychological test.