Development and testing of a de novo clinical staging system for podoconiosis (endemic non-filarial elephantiasis)

Objective To develop and test a robust clinical staging system for podoconiosis, a geochemical disease in individuals exposed to red clay soil. Methods We adapted the Dreyer system for staging filarial lymphoedema and tested it in four re-iterative field tests conducted in an area of high-podoconiosis prevalence in Southern Ethiopia. The system has five stages according to proximal spread of disease and presence of dermal nodules, ridges and bands. We measured the 1-week repeatability and the inter-observer agreement of the final staging system. Results The five-stage system is readily understood by community workers with little health training. Kappa for 1-week repeatability was 0.88 (95% CI 0.80-0.96), for agreement between health professionals was 0.71 (95% CI 0.60-0.82), while that between health professionals and community podoconiosis agents without formal health training averaged 0.64 (95% CI 0.52-0.78). Conclusions This simple staging system with good inter-observer agreement and repeatability can assist in the management and further study of podoconiosis.