A comparison of four tests of cognition

Background: previous studies have shown that a Mini Mental State Examination (MMSE) score of <24/30 and inability to copy intersecting pentagons (IP) predicts inability to perform spirometry. We hypothesised that clock drawing tests (CLOX 1 and 2), being validated tests of cognitive executive function, might predict spirometry performance with a higher sensitivity and specificity than the MMSE or IP. Methods: we studied 113 (84 females) spirometry-naı̈ve inpatients, mean age of 84 years (range 74–97). All performed the MMSE, IP, CLOX 1 and 2 and then attempted to perform assisted spirometry to the American Thoracic Society/European Respiratory Society standard. Results: of 113, 49 met the criteria for adequate spirometry. Using normative thresholds for probable impairment, inability to perform spirometry was predicted by MMSE <24/30 with a sensitivity of 81% and specificity of 90% (P< 0.0000); by inability to copy IP with a sensitivity of 92% and specificity of 100% (P< 0.0000); by CLOX1 <10/15 with a sensitivity of 81% and specificity of 49% (P< 0.001); and by CLOX2 <12/15 with a sensitivity of 63% and specificity of 65% (P< 0.001). Conclusion: CLOX tests did not perform better than MMSE and IP to identify subjects unlikely to be able to perform spirometry. Achieving assisted spirometry from the naı̈ve state in old age might be more determined by global cognitive function and ideo-motor praxis than by executive control function.