Background: Assessing function is a crucial element in the diagnosis of dementia. This information is usually obtained from key informants. However, reliable informants are not always available.
Methods: A 10-item semi-structured home interview (the CHIF, or Clinician Home-based Interview to assess Function) to assess function primarily by measuring instrumental activities of daily living directly was developed and tested for inter-rater reliability and validity as part of the Indianapolis-Ibadan dementia project. The primary validity measurements were correlations between scores on the CHIF and independently gathered scores on the Blessed Dementia Scale (from informants) and the Mini-mental State Examination (MMSE). Sensitivities and specificities of scores on the CHIF and receiver operator characteristic (ROC) curves were constructed with dementia as the dependent variable.
Results: Inter-rater reliability for the CHIF was high (Pearson's correlation coefficient 0.99 in Indianapolis and 0.87 in Ibadan). Internal consistency, in both samples, was good (Cronbach's alpha 0.95 in Indianapolis and 0.83 in Ibadan). Scores on the CHIF correlated well with the Blessed Dementia scores at both sites (-0.71, p < 0.0001 for Indianapolis and -0.56, p < 0.0001 for Ibadan) and with the MMSE (0.75, p < 0.0001 for Indianapolis and 0.44, p < 0.0001 for Ibadan). For all items at both sites, the subjects without dementia performed significantly better than those with dementia. The area under the ROC curve for dementia diagnosis was 0.965 for Indianapolis and 0.925 for Ibadan.
Conclusion: The CHIF is a useful instrument to assess function directly in elderly participants in international studies, particularly in the absence of reliable informants.