The effectiveness of sanitary inspections as a risk assessment tool for thermotolerant coliform bacteria contamination of rural drinking water

A review of data from West Bengal, India

Christian Snoad, Corey Nagel, Animesh Bhattacharya, Evan Thomas

Research output: Contribution to journalReview article

4 Citations (Scopus)

Abstract

The use of sanitary inspections combined with periodic water quality testing has been recommended in some cases as screening tools for fecal contamination. We conducted sanitary inspections and tested for thermotolerant coliforms (TTCs), a fecal indicator bacteria, among 7,317 unique water sources in West Bengal, India. Our results indicate that the sanitary inspection score has poor ability to identify TTC-contaminated sources. Among deep and shallow hand pumps, the area under curve (AUC) for prediction of TTC > 0 was 0.58 (95% confidence interval [CI] = 0.53-0.61) and 0.58 (95% CI = 0.54-0.62), respectively, indicating that the sanitary inspection score was only marginally better than chance in discriminating between contaminated and uncontaminated sources of this type. A slightly higher AUC value of 0.64 (95% CI=0.57-0.71) was observed when the sanitary inspection score was used for prediction of TTC > 0 among the gravity-fed piped sources. Among unprotected springs (AUC = 0.48, 95% CI = 0.38-0.55) and unprotected dug wells (AUC = 0.41, 95% CI = 0.20-0.66), the sanitary inspection score performed more poorly than chance in discriminating between sites with TTC < 1 and TTC > 0. Aggregating over all source types, the sensitivity (true positive rate) of a high/very high sanitary inspection score for TTC contamination (TTC > 1 CFU/100 mL) was 29.4% and the specificity (true negative rate) was 77.9%, resulting in substantial misclassification of the sites when using the established risk categories. These findings suggest that sanitary surveys are inappropriate screening tools for identifying TTC contamination at water points.

Original languageEnglish (US)
Pages (from-to)976-983
Number of pages8
JournalAmerican Journal of Tropical Medicine and Hygiene
Volume96
Issue number4
DOIs
StatePublished - 2017

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Drinking Water
India
Area Under Curve
Confidence Intervals
Bacteria
Water
Water Quality
Gravitation
Hand

ASJC Scopus subject areas

  • Parasitology
  • Infectious Diseases
  • Virology

Cite this

The effectiveness of sanitary inspections as a risk assessment tool for thermotolerant coliform bacteria contamination of rural drinking water : A review of data from West Bengal, India. / Snoad, Christian; Nagel, Corey; Bhattacharya, Animesh; Thomas, Evan.

In: American Journal of Tropical Medicine and Hygiene, Vol. 96, No. 4, 2017, p. 976-983.

Research output: Contribution to journalReview article

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abstract = "The use of sanitary inspections combined with periodic water quality testing has been recommended in some cases as screening tools for fecal contamination. We conducted sanitary inspections and tested for thermotolerant coliforms (TTCs), a fecal indicator bacteria, among 7,317 unique water sources in West Bengal, India. Our results indicate that the sanitary inspection score has poor ability to identify TTC-contaminated sources. Among deep and shallow hand pumps, the area under curve (AUC) for prediction of TTC > 0 was 0.58 (95{\%} confidence interval [CI] = 0.53-0.61) and 0.58 (95{\%} CI = 0.54-0.62), respectively, indicating that the sanitary inspection score was only marginally better than chance in discriminating between contaminated and uncontaminated sources of this type. A slightly higher AUC value of 0.64 (95{\%} CI=0.57-0.71) was observed when the sanitary inspection score was used for prediction of TTC > 0 among the gravity-fed piped sources. Among unprotected springs (AUC = 0.48, 95{\%} CI = 0.38-0.55) and unprotected dug wells (AUC = 0.41, 95{\%} CI = 0.20-0.66), the sanitary inspection score performed more poorly than chance in discriminating between sites with TTC < 1 and TTC > 0. Aggregating over all source types, the sensitivity (true positive rate) of a high/very high sanitary inspection score for TTC contamination (TTC > 1 CFU/100 mL) was 29.4{\%} and the specificity (true negative rate) was 77.9{\%}, resulting in substantial misclassification of the sites when using the established risk categories. These findings suggest that sanitary surveys are inappropriate screening tools for identifying TTC contamination at water points.",
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