Abstract
Purpose
The true disease status of a population with suspected microbial keratitis (MK) cannot be verified. There is not an accurate (gold) reference standard to confirm infection and inter-test comparisons of sensitivity and specificity therefore lead to bias with questionable estimates of test utility. We present an alternative method to report results.
Methods
We used a decision to treat as the definition for MK. We retrospectively compared the results of corneal culture and polymerase chain reaction (PCR) as these are objective tests available for the three principal groups of pathogens. We then estimated the potential contribution of positive results, either alone or in combination, to support the working diagnosis.
Results
We included 2021 (77.4%) eyes with suspected bacterial keratitis, 365 (14.0%) with suspected acanthamoeba keratitis, and 226 (8.6%) with suspected fungal keratitis, all treated between July 2013 and December 2019. In these groups, there were 51.6% positive culture and 6.5% positive PCR results for bacteria, 19.0% and 40.5% for acanthamoeba, and 28.3% and 15.0% for fungi. Between groups the differences in the proportions of positive results from culture and PCR was statistically significant (P < 0.001). The added benefit of PCR to the result of culture in identifying a potential pathogen was 1.4% for bacteria (P = 0.6292), 24.4% for acanthamoeba (P = 0.0001), and 5.8% for fungi (P = 0.3853).
Conclusions
For suspected MK a comparison of the test positivity rate is an easily comprehensible outcome measure of test utility.
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Acknowledgements
The views expressed are those of the author(s) and not necessarily those of the NIHR or the Department of Health and Social Care. ST received salary support from the Department of Health through an award made by the National Institute for Health Research to Moorfields Eye Hospital NHS Foundation Trust and the University College London Institute of Ophthalmology for a Specialist Biomedical Research Centre for Ophthalmology. CB is part funded by the National Institute for Health Research (NIHR) Biomedical Research Centre at The Royal Marsden NHS Foundation Trust and the Institute of Cancer Research, London.
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ST and CB performed the literature search. ST and CB were responsible for the study concept and design. ST and JT collected the data. ST, SD and JT accessed and verified the data. ST and CB performed the statistical analysis. ST, CB, SD and JT were responsible for the interpretation of the data. ST drafted the manuscript. All authors critically revised the manuscript for important intellectual content. ST was the study supervisor. All authors reviewed the manuscript and had final responsibility for the decision to submit for publication.
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Tuft, S., Bunce, C., De, S. et al. Utility of investigation for suspected microbial keratitis: a diagnostic accuracy study. Eye 37, 415–420 (2023). https://doi.org/10.1038/s41433-022-01952-4
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DOI: https://doi.org/10.1038/s41433-022-01952-4
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