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A.W. Solomon, N.D. E. Alexander, M.J. Burton, B. Munoz, R.L. Bailey, S.K. West, A. Foster, D.C. W. Mabey, WT/BWF Trachoma Study Group; A Rapid Field–Based Assay for Ocular C Trachomatis Infection for Use in Trachoma Control Programs: Rationale and Requirements . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5020.
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Purpose: Trachoma is caused by Chlamydia trachomatis; antibiotics are part of the control strategy. However, the relationship between infection and clinical signs is imperfect, particularly in low prevalence settings and after one or more rounds of antibiotics. Existing tests for infection are unsuitable for use by trachoma control programs. A rapid, reliable, cheap test for ocular C. trachomatis that could be used in the field to estimate community prevalence of infection would ensure that antibiotics are given to communities that need them most. Methods: From each of three datasets from trachoma–endemic communities in Tanzania and The Gambia, we repeatedly (10,000 times) simulated sampling 50 children aged 1–9. For each sample, the decision that would be made to treat or not treat the community based on the prevalence of TF in the sample was compared with the decision that would be made based on the community prevalence of ocular C. trachomatis infection, by PCR. For each child in each sample we also simulated a result for a putative C. trachomatis dipstick test, based on assumed values for its sensitivity and specificity. As for TF, we compared treatment decisions based on dipstick to those based on PCR. Results: Receiver operating characteristic plots (showing the trade–off between sensitivity and specificity of the method at decision–to–treat–the–community level) demonstrate that a dipstick test that was 97.5% specific and only 80% sensitive (at individual level) would be an advance over using TF. Conclusions: These performance characteristics are achievable with currently available technology. The dipstick could be used by the same or lower cadre of staff as those who currently undertake surveys of TF prevalence, and would not be subject to the same degree of observer bias. Further research to develop dipsticks for use by trachoma control programs is warranted.
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