Enumeration of non-communicable disease in rural South Africa by electronic data linkage and capture-recapture techniques

Non-communicable diseases (NCDs) are becoming increasingly common and important in developing countries, yet their enumeration is problematic. We have attempted to enumerate NCD patients in a rural district of KwazuluNatal, South Africa, using the techniques of electronic data linkage and capture-recapture (CR). We examined four major NCDs (hypertension, diabetes, asthma and epilepsy). Basic patient details were recorded onto EpiInfo software over a 6-week period, from the main hospital clinic at Hlabisa, as well as the 10 outlying peripheral health clinics. Using electronic data linkage of lists from the main hospital, the peripheral clinics, and repeat prescription cards, a district NCD register was produced of 2455 patients. The mean age was 51 ± 16 years (1 SD) and 76% were female. Of the total NCD patients, 62% had hypertension (age 57 ± 12 years, 82% female), 16% epilepsy (age 35 ± 17 years, 49% female), 13% asthma (age 45 ± 19 years, 60% female) and 12% diabetes (age 54 ± 13 years, 61% female). Estimated population crude prevalence rates for known NCD cases on the register were 7.4% for hypertension, epilepsy 0.2%, asthma 0.2% and diabetes 0.2%. We also attempted a CR analysis to assess completeness of data, by comparing overlap between patients attending peripheral clinics, and the central Hlabisa Hospital clinic. Matching by name, age, and diagnosis proved feasible, but there was little overlap, and CR calculations were invalid because of the relative independence of sources. We conclude that NCDs are common in rural Africa, and that a simple NCD district register is a potentially feasible and inexpensive option. Capture-recapture analysis is feasible, but requires suitable lists with acceptable overlap of patients.