Measuring endemicity and burden of leprosy across countries and regions: A systematic review and Delphi survey

Abstract

Background: Leprosy is a chronic infectious disease caused by Mycobacterium leprae, the annual new case detection in 2019 was 202,189 globally. Measuring endemicity levels and burden in leprosy lacks a uniform approach. As a result, the assessment of leprosy endemicity or burden are not comparable over time and across countries and regions. This can make program planning and evaluation difficult. This study aims to identify relevant metrics and methods for measuring and classifying leprosy endemicity and burden at (sub)national level.

Methods: We used a mixed-method approach combining findings from a systematic literature review and a Delphi survey. The literature search was conducted in seven databases, searching for endemicity, burden and leprosy. We reviewed the available evidence on the usage of indicators, classification levels, and scoring methods to measure and classify endemicity and burden. A two round Delphi survey was conducted to ask experts to rank and weigh indicators, classification levels, and scoring methods.

Results: The literature review showed variation of indicators, levels, and cut-off values to measure leprosy endemicity and/or burden. The most used indicators for endemicity include new case detection rate (NCDR), new cases among children and new cases with grade 2 disability. For burden these include NCDR, MB cases, and prevalence. The classification levels 'high' and 'low' were most important. It was considered most relevant to use separate scoring methods for endemicity and burden. The scores would be derived by use of multiple indicators.

Conclusion: There is great variation in the existing method for measuring endemicity and burden across countries and regions. Our findings contribute to establishing a standardized uniform approach to measure and classify leprosy endemicity and burden at (sub)national level, which would allow effective communication and planning of intervention strategies.

Fig 1. PRISMA Flow Diagram of systematic literature review.

Fig 2

Indicators (A), classification levels (B) and scoring methods (C) used to classify endemicity and burden of leprosy. The bars represent the number of articles that used a particular indicator, classification level, or scoring method to classify endemicity (red) or burden (blue). An article could mention multiple indicators and classification levels. Other indicators include cure rate (2; endemicity), new cases with dimorphic clinical form (2; endemicity), trend in proportion of new cases with a single lesion at time of diagnosis (1; endemicity), and prevalence/detection ratio (1; burden).