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A full-scale survey, in Kelibia, Tunisia, screening 34,874 persons started on July 1, 1985. The accuracy of this survey was evaluated by a second survey using a randomized sample of 1,673 subjects (control survey). Better selection and training of the interviewers during the control survey led to a higher positive predictive value with no modification in prevalence ratios of neurologic disorders. The control survey helped to validate the full-scale survey data which were then used to establish the prevalence ratios of major neurologic disorders in Kelibia. Prevalence ratios, age-adjusted to the WHO population, were compared to those of studies using similar methodology. Migraine prevalence ratios in Nigeria, Ecuador, and Kelibia were equivalent. Epilepsy and Parkinson''s disease prevalence ratios were close to those of other similar studies. The stroke prevalence ratio was low, compared to other studies, but was not the lowest. It seems that in Kelibia, stroke does not constitute a public health problem as it does in the USA or urban China. The large full-scale survey, in Kelibia, provided estimates of prevalence ratios for stroke, epilepsy, migraine and other common neurologic disorders for comparisons with other countries. However, definitions of neurologic disorders and diagnostic criteria differ from one study to another making difficult the comparison of results between different countries. Had the WHO protocol developed well-defined criteria and a standardized neurologic examining tool, more accurate comparisons could have been made.

The Alzheimer's Disease Assessment Scale's cognitive subscale (ADAS-Cog) is the most widely used instrument for screening cognitive dysfunction in Alzheimer's disease. The aim of the present study was to develop an Arabic version of this scale (A-ADAS-Cog), examine its psychometric properties (reliability and validity), and provide normative data. The A-ADAS-Cog), an Arabic version of the Mini-Mental State Examination (A-MMSE), and a Standardized Clinical Dementia Rating Scale (CDR) were administered to three Tunisian groups: 124 normal controls (NC), 33 patients with non-Alzheimer dementia (N-AD), and 25 patients with Alzheimer's disease (AD). The A-ADAS-Cog scores were significantly affected by age and education. A correction table was constructed to control these effects. The results showed that the A-ADAS-Cog has good internal consistency and reliability (α= 0.82 for AD). The test-retest reliability of the A-ADAS-Cog was stable over time (r = 0.97). An evaluation of the construct validity of the A-ADAS-Cog using principal component analysis led to a solution with three factors (memory, language and praxis), which explained 72% of the variance. The concurrent validity of the A-ADAS-Cog was established using the A-MMSE score (r = -0.86), CDR Sum of Boxes score (CDR-SB; r = 0.87), and global CDR score (CDR-Global; r = 0.74). Finally, the A-ADAS-Cog has an excellent discriminating power in the diagnosis of AD (ROC area = 0.92). A cut-off score of 10 (sensitivity = 84% and specificity = 91%) is indicated for the screening of the AD. Overall, the results indicated that the A-ADAS-Cog is psychometrically reliable and valid and provides promising results for screening of dementia in Arabic speaking patients.

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