Capture-recapture method to assess the prevalence of disabled leprosy patients

The capture-recapture technique was applied in estimating the prevalence of disabled leprosy patients in four States in Northern Nigeria. A two-sample capture-recapture method, using data from hospital admissions during 1997 and 1998 in three leprosy referral hospitals, and from a sample survey on leprosy patients with disabilities in the clinics in 1999. In the sample, 1395 (ex) leprosy patients were found, 393 with a disability. Of these 393 patients, 47 had been admitted during 1997 and 1998 to one of three leprosy referral hospitals. In these hospitals, 151 individuals from the 24 study Local Government Areas (LGA) in four states of Northern Nigeria were admitted in 1997 and 1998. Using the Peterson estimator, we calculated the number of unknown disabled leprosy patients in the studied LGAs to be 1262 (95% confidence interval 991-1533). This was nearly four times greater than the field reported figure. The capture-recapture method can be applied in a leprosy care programme. Limitations of the method are the completeness of reporting after invitation in the field, as well as the probable biased sample of leprosy patients admitted to hospital. Our finding implies that relying on patients to report for prevention of disabilities and rehabilitation to the clinics, causes the real size of the problem to be underestimated by a factor of 3-4. We recommend the use of a special 'care' register for disabled leprosy patients to better address their needs for prevention of disabilities and rehabilitation.