A comparison of four tests of cognition as predictors of inability to learn to use a metered dose inhaler in old age

Background: Previous studies have shown that a Mini Mental State Examination (MMSE) score of < 24/30 and inability to copy intersecting pentagons (IP) predict inability to learn to use inhaler devices. We hypothesised that clock drawing tests (CLOX 1 and 2), being validated tests of cognitive executive function, might predict competent inhaler acquisition with a higher sensitivity and specificity than the MMSE or IP. Methods: We studied 80 (63 women) inhaler-naive inpatients, mean age 83 years (range 75-97 years). All performed the MMSE, IP, CLOX 1 and 2, before receiving standardised demonstration, instruction and assessment in the use of a metered dose inhaler (MDI). Results: A total of 28/80 (35%) patients were able to acquire a satisfactory MDI technique. Using normative thresholds for impairment, the sensitivity and specificity (% with 95% confidence intervals) of the cognitive scores in predicting inability were: MMSE < 24 sensitivity 57 (42-71), specificity 76 (57-88), p = 0.04; IP sensitivity 75 (60-85), specificity 79 (59-91), p = 0.0000; CLOX1 < 10 sensitivity 83 (69-91), specificity 57 (37-75), p = 0.0004; CLOX2 < 12 sensitivity 58 (43-71), specificity 64 (44-81), p = 0.05. Conclusion: CLOX tests did not perform better than MMSE and IP, to identify patients who are unlikely to be able to acquire MDI technique from a single episode of training. In clinical practice, most patients with an MMSE < 24 or negative IP will not be able to learn MDI technique. In this study, IP had the best overall predictive value.