The Prudhoe Cognitive Function Test, a scale to assess cognitive function in adults with Down's syndrome: inter-rater and test–retest reliability

Background The Prudhoe Cognitive Function Test (PCFT) was designed to measure cognitive function in subjects with all degrees of intellectual disability (ID) and to be administered by non‐specialist raters. The aim of the present study was to measure the test–retest and inter‐rater reliability of the PCFT. Methods Three raters, one a specialist and two non‐specialists, administered the PCFT to 14 subjects with Down's syndrome on two occasions separated by 4 weeks. Results The intra‐class correlation coefficients (ICCs) between the rater pairs (n = 3) were 0.99, 0.99 and 0.98 (P < 0.01). Floor effects were recorded for two items. The ICC for test–retest reliability was 0.99 (P < 0.01). Conclusions The PCFT is a highly reliable instrument when used by either specialist or non‐specialist raters. It has excellent temporal stability.