VALIDATION OF A TELEPHONE COGNITIVE ASSESSMENT BATTERY

OBJECTIVE: To present and evaluate an instrument, the Telephone Cognit ive Assessment Battery (TCAB), designed to be administered over the te lephone to assess the cognitive status of older individuals. The TCAB addresses mental status, reasoning and executive ability, primary and secondary memory, and language. It consists of six neuropsychological tests and takes approximately 15 to 20 minutes to complete. DESIGN: Th e instrument is evaluated with a comparative cross-sectional design, w ith data collected both prospectively and retrospectively. SETTING: Th e University Hospitals of Cleveland/Case Western Reserve University Al zheimer Center Research Registry. PARTICIPANTS: Forty Alzheimer's Dise ase cases selected from among those most recently recruited into the R egistry and 40 cognitively intact Registry controls. Controls were sel ected randomly so that the two groups had similar distributions of age , sex, and education. MEASUREMENTS: The cognitive status of all partic ipants was assessed utilizing both the TCAB and the usual in-person. R egistry evaluation, which includes medical history data and in-person assessment of cognitive status. In order to measure the potential lear ning effect of repeated testing, half oi the cases and half of the con trols were recruited and assessed over the telephone with the TCAB bef ore their in-person Registry evaluation (with a waiting period of at l east 2 weeks between evaluations), whereas the other two halves receiv ed the TCAB after they had become part of the Registry. The TCAB was a dministered to all participants by a single investigator. Two clinical evaluators, blinded to the Registry diagnosis of the subjects, indepe ndently classified the subjects as cognitively impaired, normal, or qu estionable on the basis of the results of the TCAB and a brief listing of medical illness and depressive symptoms. A final classification wa s achieved through consensus and subsequently compared with the Regist ry diagnosis, taken here to be the gold standard. RESULTS: Test scores of subjects assessed by TCAB before receiving the in-person assessmen t were compared with those of subjects receiving the in-person assessm ent first. There were no significant differences between mean scores o f the two groups (those with TCAB first and those with TCAB last) for either cases or normal controls. High values of the kappa statistic we re obtained for the two initial evaluators of the TCAB classification, demonstrating excellent interrater reliability. Regarding the reconci led TCAB classification, the ability of the TCAB to correctly classify subjects according to cognitive status, while controlling for potenti al confounders such as age and educational level, was assessed by mean s oi discriminant analysis techniques. Knowledge of the TCAB classific ation and age allowed the correct classification of 95% of the partici pants; this was not significantly unproved by knowledge of other poten tial determinants. Sensitivity and specificity were calculated under t wo schema for classifying those subjects in the ''questionable'' categ ory. Positive and negative predictive values of the TCAB were computed assuming a prevalence of cognitive impairment of 10% in the older pop ulation. High negative predictive values (over 99%) were obtained unde r both schema, whereas the positive predictive values were seen to be more dependent on the classification of questionables.CONCLUSION Resea rch studies involving ascertainment of cognitive status of older peopl e, particularly those that require periodic follow-up, such as those f ocusing on healthy aging, commonly suffer from lack of representativen ess of subjects, often brought about by problems related to mobility o f potential participants. It is also crucial that normal individuals w ho are recruited initially to serve as controls in epidemiologic studi es of dementing illnesses be reevaluated periodically, and this may be hindered by the same obstacles. The ability to measure cognitive stat us by telephone would seem to aid in the solution to these problems as long as the telephone assessment is valid. The TCAB appears to discri minate between mildly cognitively impaired and healthy normal subjects in a population of older participants of research registries in much the same way as in-person assessment. Thus, when administered by a tra ined individual, it of offers a valid and reliable means of assessing the cognitive status of these types of older subjects by telephone. Fu rther work is needed to demonstrate its applicability to other, e.g., community-wide, settings.