Epilepsy prevalence in rural Zambia: a door-to-door survey

OBJECTIVES To identify people with epilepsy (PWE) in our Zambian catchment area of 55 000 people. METHODS A nine-item, previously validated screening instrument for detecting epilepsy in developing countries was forward-and-back translated into Chitonga. Early piloting indicated poor specificity among children, so three questions were added. Local census data were used to estimate the population at risk. Community health workers conducted screening interviews with household heads. All positive screens were referred for physician assessment. A blinded neurologist assessed a randomly selected subset (100 positives, 50 negatives) to determine screening instrument characteristics. RESULTS We identified 799 people with possible epilepsy (unadjusted prevalence 14.5/1000). The adapted instrument exhibited 86% specificity (adjusted prevalence 12.5/1000). False positives occurred primarily among children who had experienced multiple malaria-associated seizures. Age-specific rates were highest for children aged 5-15 years (26.2/1000) and for people over 65 years (15.9/1000). Males were disproportionately represented (55.8% vs. 44.2%, P < 0.05), although this trend reversed after childbearing age. CONCLUSION Even using a relatively conservative definition, we identified almost 700 PWE. Use of the recommended epidemiological definitions would likely have yielded higher prevalence rates. The age-specific prevalence did not follow patterns described where neurocysticercosis is the commonest cause of epilepsy. Trends in age- and gender-specific prevalence may offer a clue to the aetiology of epilepsy in this region.