The objective of the study was to assess the validity and reliability of the clock drawing test (CDT) in comparison with the Mini-Mental State Examination (MMSE) as a screening tool for cognitive impairment in patients with fibromyalgia (FM).
Fifty female patients with FM and 51 healthy female controls were enrolled in the study. Cognitive functioning of the subjects was evaluated by the CDT and the MMSE. Each CDT was scored according to 3 different clock scoring methods (Shulman, Sunderland, and Watson). Two experienced clinicians scored the CDTs to evaluate the interrater reliability. Validity, sensitivity, specificity, and predictive accuracy of each clock scoring method were analyzed.
The Shulman score had the highest correlation with the MMSE score (r =0.65, P < .01). The Shulman and Sunderland methods had significantly the largest areas under the receiver operating characteristic curve (0.82 and 0.81, respectively; P = .000). They also had the highest sensitivity (68.8% and 65.5%, respectively) and specificity (84.2%, and 84.1%, respectively). The interrater correlation coefficients were high for all 3 clock scoring methods.
The CDT has been proven to be a valid and reliable tool for screening cognitive impairment in FM patients. The Shulman or Sunderland scoring methods are more appropriate than the Watson scoring method. Further studies are needed for using the CDT to detect cognitive impairment in patients with FM.