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Accuracy of the H2S test: a systematic review of the influence of bacterial density and sample volume

Accuracy of the H2S test: a systematic review of the influence of bacterial density and sample volume
Accuracy of the H2S test: a systematic review of the influence of bacterial density and sample volume
The presence/absence hydrogen sulphide test (P/A H2S) is widely used as a low-cost alternative faecal indicator test in remote and resource-poor settings. The aim of the paper is to assess how bacterial density and sample volume affect its accuracy. Based on a systematic search, we identified studies that tested water samples (n = 2,034) using both the P/A H2S test and recognised tests for thermotolerant coliforms (TTC) or E. coli. We calculated P/A H2S test specificity and sensitivity against a range of TTC and E. coli densities. For two studies, we compared this with sensitivity and specificity estimates for simulated 100 and 20 ml presence/absence tests. For most of the 19 included studies, as the threshold used to define contamination increased from 1 to 100 cfu/100 ml, P/A H2S test sensitivity increased but specificity decreased. Similarly, the simulation indicated that increasing test volumes from 20 to 100 ml increased sensitivity but reduced specificity. There was potential for bias, for example from lack of blinding during test interpretation, in most of the studies reviewed. In assessing the P/A H2S test as an alternative to standard methods, careful consideration of likely indicator bacteria levels and sample volume is required.
E. coli, H2S test, sensitivity, specificity, thermotolerant coliforms, water quality
1477-8920
173-185
Yang, Hong
2ea2c94c-8d28-4555-98f9-59b615b0cee7
Wright, J.A.
94990ecf-f8dd-4649-84f2-b28bf272e464
Bain, Robert
c74dff86-c531-4941-9453-77a733634750
Pedley, Steve
4ad4d2f3-3e70-4f82-8b3b-c2d2f2b5df5a
Elliott, John
589c5ac2-c67e-4eb1-aa07-c07583997af5
Gundry, Stephen
7146591d-c1c8-4160-96a6-26d5ce136ab6
Yang, Hong
2ea2c94c-8d28-4555-98f9-59b615b0cee7
Wright, J.A.
94990ecf-f8dd-4649-84f2-b28bf272e464
Bain, Robert
c74dff86-c531-4941-9453-77a733634750
Pedley, Steve
4ad4d2f3-3e70-4f82-8b3b-c2d2f2b5df5a
Elliott, John
589c5ac2-c67e-4eb1-aa07-c07583997af5
Gundry, Stephen
7146591d-c1c8-4160-96a6-26d5ce136ab6

Yang, Hong, Wright, J.A., Bain, Robert, Pedley, Steve, Elliott, John and Gundry, Stephen (2013) Accuracy of the H2S test: a systematic review of the influence of bacterial density and sample volume. Journal of Water and Health, 11 (2), 173-185. (doi:10.2166/wh.2013.225).

Record type: Article

Abstract

The presence/absence hydrogen sulphide test (P/A H2S) is widely used as a low-cost alternative faecal indicator test in remote and resource-poor settings. The aim of the paper is to assess how bacterial density and sample volume affect its accuracy. Based on a systematic search, we identified studies that tested water samples (n = 2,034) using both the P/A H2S test and recognised tests for thermotolerant coliforms (TTC) or E. coli. We calculated P/A H2S test specificity and sensitivity against a range of TTC and E. coli densities. For two studies, we compared this with sensitivity and specificity estimates for simulated 100 and 20 ml presence/absence tests. For most of the 19 included studies, as the threshold used to define contamination increased from 1 to 100 cfu/100 ml, P/A H2S test sensitivity increased but specificity decreased. Similarly, the simulation indicated that increasing test volumes from 20 to 100 ml increased sensitivity but reduced specificity. There was potential for bias, for example from lack of blinding during test interpretation, in most of the studies reviewed. In assessing the P/A H2S test as an alternative to standard methods, careful consideration of likely indicator bacteria levels and sample volume is required.

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More information

e-pub ahead of print date: 1 June 2013
Keywords: E. coli, H2S test, sensitivity, specificity, thermotolerant coliforms, water quality
Organisations: Geography & Environment, PHEW – P (Population Health)

Identifiers

Local EPrints ID: 352165
URI: https://eprints.soton.ac.uk/id/eprint/352165
ISSN: 1477-8920
PURE UUID: 77b89090-a2ff-4346-a923-05b8762ec47d
ORCID for J.A. Wright: ORCID iD orcid.org/0000-0002-8842-2181

Catalogue record

Date deposited: 07 May 2013 12:10
Last modified: 20 Jul 2019 00:57

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Contributors

Author: Hong Yang
Author: J.A. Wright ORCID iD
Author: Robert Bain
Author: Steve Pedley
Author: John Elliott
Author: Stephen Gundry

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