A systematic review of the diagnostic accuracy of the H2S test versus indicator bacteria tests for faecal contamination of water

Abstract

The H2S test, a simple, low-cost field test, is used in many remote and developing country settings to test for the faecal contamination of drinking-water. However, its diagnostic accuracy remains uncertain. To provide more guidance on its use, we assessed the diagnostic accuracy of the H2S test versus indicator bacterial tests for E. coli or thermotolerant coliforms (TTC). We screened 661 abstracts and identified 51 relevant studies based on 13,853 water samples. The overall test sensitivity and specificity (95% CI) was 0.87 (0.80-0.92) and 0.82 (0.72-0.90) relative to TTC and 0.88 (0.77-0.94) and 0.75 (0.55–0.88) relative to E. coli tests. The test’s diagnostic accuracy varied significantly and substantially between studies. Little of this variation was explained by testing procedures, study quality or the nature of the samples processed. We recommended that users should benchmark its accuracy before using in a new setting