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Performance evaluation of automated urine microscopy as a rapid, non-invasive approach for the diagnosis of non-gonococcal urethritis.

Pond, MJ; Nori, AV; Patel, S; Laing, K; Ajayi, M; Copas, AJ; Butcher, PD; Hay, P; Sadiq, ST (2015) Performance evaluation of automated urine microscopy as a rapid, non-invasive approach for the diagnosis of non-gonococcal urethritis. Sexually Transmitted Infections, 91 (3). pp. 165-170. ISSN 1368-4973 https://doi.org/10.1136/sextrans-2014-051761
SGUL Authors: Butcher, Philip David Hay, Phillip Edward Laing, Kenneth Sadiq, Syed Tariq Pond, Marcus James

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Abstract

OBJECTIVES: Gram-stained urethral smear (GSUS), the standard point-of-care test for non-gonococcal urethritis (NGU) is operator dependent and poorly specific. The performance of rapid automated urine flow cytometry (AUFC) of first void urine (FVU) white cell counts (UWCC) for predicting Mycoplasma genitalium and Chlamydia trachomatis urethral infections was assessed and its application to asymptomatic infection was evaluated. METHODS: Receiver operating characteristic curve analysis, determining FVU-UWCC threshold for predicting M. genitalium or C. trachomatis infection was performed on 208 'training' samples from symptomatic patients and subsequently validated using 228 additional FVUs obtained from prospective unselected patients. RESULTS: An optimal diagnostic threshold of >29 UWC/µL gave sensitivities and specificities for either infection of 81.5% (95% CI 65.1% to 91.6%) and 85.8% (79.5% to 90.4%), respectively, compared with 86.8% (71.1% to 95%) and 64.7% (56.9% to 71.7%), respectively, for GSUS, using the training set samples. FVU-UWCC demonstrated sensitivities and specificities of 69.2% (95% CI 48.1% to 84.9%) and 92% (87.2% to 95.2%), respectively, when using validation samples. In asymptomatic patients where GSUS was not used, AUFC would have enabled more infections to be detected compared with clinical considerations only (71.4% vs 28.6%; p=0.03). The correlation between UWCC and bacterial load was stronger for M. genitalium compared with C. trachomatis (τ=0.426, p≤0.001 vs τ=0.295, p=0.022, respectively). CONCLUSIONS: AUFC offers improved specificity over microscopy for predicting C. trachomatis or M. genitalium infection. Universal AUFC may enable non-invasive diagnosis of asymptomatic NGU at the PoC. The degree of urethral inflammation exhibits a stronger association with pathogen load for M. genitalium compared with C. trachomatis.

Item Type: Article
Additional Information: This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 4.0) license, which permits others to distribute, remix, adapt and build upon this work, for commercial use, provided the original work is properly cited. See: http://creativecommons.org/ licenses/by/4.0
Keywords: CHLAMYDIA TRACHOMATIS, DIAGNOSIS, M GENITALIUM, MOLECULAR TECHNIQUES, URETHRITIS, Adult, Automation, Laboratory, Chlamydia Infections, Flow Cytometry, Humans, Leukocyte Count, Male, Microscopy, Mycoplasma Infections, ROC Curve, Sensitivity and Specificity, Urethritis, Urine, Urine, Humans, Chlamydia Infections, Mycoplasma Infections, Urethritis, Microscopy, Leukocyte Count, Flow Cytometry, Sensitivity and Specificity, ROC Curve, Adult, Male, Automation, Laboratory, Public Health, 1103 Clinical Sciences, 1117 Public Health And Health Services, 1108 Medical Microbiology
SGUL Research Institute / Research Centre: Academic Structure > Infection and Immunity Research Institute (INII)
Journal or Publication Title: Sexually Transmitted Infections
ISSN: 1368-4973
Language: eng
Dates:
DateEvent
22 January 2015Published
Publisher License: Creative Commons: Attribution 4.0
Projects:
Project IDFunderFunder ID
G0901608Medical Research Councilhttp://dx.doi.org/10.13039/501100000265
UNSPECIFIEDBiotechnology and Biological Sciences Research Councilhttp://dx.doi.org/10.13039/501100000268
PubMed ID: 25614466
Web of Science ID: WOS:000353166000008
Go to PubMed abstract
URI: https://openaccess.sgul.ac.uk/id/eprint/107570
Publisher's version: https://doi.org/10.1136/sextrans-2014-051761

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