Nerve function impairment in leprosy: design, methodology, and intake status of a prospective cohort study of 2664 new leprosy cases in Bangladesh (The Bangladesh Acute Nerve Damage Study).

The Bangladesh Acute Nerve Damage Study (BANDS) is a prospective cohort study designed to investigate epidemiological, diagnostic, therapeutic and operational aspects of acute nerve function impairment in leprosy. The study is based at a single centre in Bangladesh, in an area with a high prevalence of leprosy. The centre, Danish Bangladesh Leprosy Mission, has a well-established vertical leprosy control programme. In this paper, the study design and methodology are described, together with definitions of nerve function impairment (NFI) used in this and subsequent papers. The study recruited 2664 new leprosy cases in a 12-month period. The male:female ratio is 1.25:1, and 17.61% of the cohort are under 15 years of age. In all, 83.33% of the cohort are paucibacillary (PB), and 16.67% multibacillary (MB). However, the MB rate amongst males is 19.72%, and amongst females is 12.85%, despite an equal period of delay to diagnosis. 55% of patients presented for treatment within 12 months of developing symptoms 6.12% of the total number of cases were smear positive, and 36.71% of the MB cases were smear positive. 9.61% of the total number of cases were graded as having World Health Organisation (WHO) disability grade 1, and 5.97% had grade 2. Amongst MB cases, 27.48% had WHO grade 1 disability present, and 18.24% had grade 2 present, compared with 6.04% and 3.51%, respectively, amongst PB cases. A total of 11.90% of the cohort had sensory NFI of any kind, and 7.39% had motor NFI. Ninety patients presented with NFI needing treatment (3.38%), and of these, 61 (67.78%) had silent NFI. MB patients had a prevalence of reaction/NFI needing treatment nearly 7 times higher than PB cases (15.32% amongst MB; 2.30% amongst PB), and males nearly double that of females (5.67% amongst males, 2.96% amongst females). The most commonly affected nerve by function impairment was the posterior tibial (sensory) with 6.46% of nerves affected (9.38% of patients), followed by the ulnar nerve with 3.23% of nerves impaired (5.56% of patients). Future research and publications, building on this foundation, will focus on the following areas: the incidence of NFI and reactive events, the risk factors for developing NFI, and the response to treatment of patients developing acute NFI.