Introduction: This study assessed five scoring methods of the Clock-Drawing test (CDT).
Material and methods: A total of 72 out-patients and 29 healthy controls were assessed three times. At Visit 1, diagnostic procedure and assessments were performed with the Clinical Global Impressions (CGI) and Global Deterioration Scale (GDS), and the CDT and the Mini Mental State Examination (MMSE) were done blinded by a nurse. At Visit 2, CDT and MMSE were repeated, and at Visit 3 the CDT, CGI and the GDS were repeated. The CDTs were then rated by physicians and nurses using five different methods of scoring. Receiver-operating characteristics curve analyses were used to assess the CDT's suitability as a screening tool. Correlations between the five CDTs, other scales and predictive values were calculated. The extent to which three-word recall could improve the predictive values was analysed.
Results: Correlations between the CDTs and the other scales were good. The predictive values were almost identical (positive values: 93-97%; negative values: 70-74%). Three-word recall improved the values. Rates of dementia in general practice and corresponding predictive values were estimated which resulted in markedly lower positive values around 60% for a rate of dementia of 20%, and 40% for a rate of dementia of 10%.
Conclusion: As predictive values were nearly identical, the shortest scoring manual (0 to 1) seems preferable.
Funding: The study was partly funded by Novartis Pharma A/S.
Trial registration: Scientific Ethical Committee, 2003-2-17.