Objectives To determine if the Clock Test, a screening test for dementia, was suitable for use in a Nigerian population. We wanted to inquire if there is a screening test that can be used to validate claims of relatively low rates of dementia in Nigerian populations.
Patients or Participants 66 subjects from 50-87 years of age were recruited from patients and families at the Jos University Teaching Hospital, Nigeria.
Interventions Administration of a questionnaire-based test adapted for use in a Nigerian population and the Clock Test to participants.
Outcome Measures Each test used predetermined scoring rules and cutoff points for dementia screening. Scores on subsets of the Clock Test and whether or not subjects had a concept of a clock were also measured.
Results Overall, 53.0% of the subjects had an abnormal Clock Test whereas 10.6% of the subjects had an abnormal questionnaire score. Only 9.1% of the subjects had abnormal scores on both tests while 45.5% of the subjects had normal scores by both tests. For Clock Test subjects ≥ 63 years of age, 37.9% had abnormal tests while only 15.0% of those ≤ 63 years of age did (χ2= 11.8, p≤.001). For questionnaire subjects ≥ 63 years of age only 6.0% had abnormal tests while only 4.5% of those ≤ 63 years of age did (χ2= 0.097, p=.75). There was an association between age and abnormal test results for the Clock Test, but not for the questionnaire. R.O.C. curve values for components of the Clock test: clock setting (0.95), clock reading (0.92) and clock drawing (0.87), showed these portions of the test were more effective in detecting abnormal performances than other aspects of the test. Of those with more than 6 years of schooling, 91.0% had a positive clock concept. Subjects that had a negative clock concept were more likely to have an abnormal Clock Test (93.3%) than an abnormal questionnaire (26.6%).
Conclusions The main finding of our study was the discrepancy between the Clock Test results and the questionnaire results. Clock Test performance appeared to be influenced by education level, indicating that the test is not applicable across cultures. The questionnaire-based test appeared to reduce the effects of illiteracy on assessing dementia in a Nigerian population. Larger studies should be done to control for how education affects dementia assessment.
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