Multiple clock drawing scoring systems: simpler is better

Abstract

The clock drawing test (CDT) is a widely used cognitive screening tool that has been well accepted among clinicians and patients for its ease of use and short administration time. Although there is ample interest in the CDT as a screening instrument, there remains a range of CDT administration and scoring systems with no consensus on which system produces the most valid results while remaining user friendly. The aims of this review are to synthesize the available evidence on CDT scoring systems' effectiveness and to recommend which system is best suited for use at the clinical frontlines. A Pubmed literature search was carried out from 2000 to 2013 including manual cross-referencing of bibliographies in order to capture studies published after Shulman's comprehensive review published in 2000. A brief summary of all original scoring systems is included, as well as a review of relevant comparative studies. The consensus from multiple comparison studies suggests that increasing the complexity of CDT scoring systems does little to enhance the test's ability to identify significant cognitive impairment. Moreover, increased complexity in scoring adds to the administration time, thereby reducing the test's utility in clinical settings. In comparing scoring systems, no system emerged as consistently superior in terms of predictive validity. The authors conclude that when scoring the CDT as a screening instrument in a primary/general medicine/community setting, simpler is better, and perhaps qualitative assessment of "normal" versus "abnormal" may be sufficient for screening purposes and the establishment of a baseline for follow-up.