Author:
Hammoudeh Yasmeen,Suresh Lakshmi,Ong Zun Zheng,Lister Michelle M.,Mohammed Imran,Thomas D. John I.,Cottell Jennifer L.,Holden Jennifer M.,Said Dalia G.,Dua Harminder S.,Jeng Ting Darren Shu
Abstract
ABSTRACTPurposeTo compare the diagnostic performance of microbiological culture and 16S/18S polymerase chain reaction (PCR)-Sanger sequencing for infectious keratitis (IK) and to analyse the effect of clinical disease severity on test performance and inter-test concordance.DesignA three-arm, diagnostic cross-sectional study.SubjectsWe included patients who presented with presumed bacterial/fungal keratitis to the Queen’s Medical Centre, Nottingham, UK, between June 2021 and September 2022.Methods/interventionsAll patients underwent simultaneous culture (either direct or indirect culture, or both) and 16S (pan-bacterial) / 18S (pan-fungal) ribosomal RNA (rRNA) PCR-Sanger sequencing. The bacterial/fungal genus and species identified on culture were confirmed using matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry. Relevant clinical data were also collected to analyze for any potential clinico-microbiological correlation.Main outcome measuresDiagnostic yield, test accuracy (including sensitivity and specificity), and inter-test agreement [including percent agreement and Cohen’s kappa (k)].ResultsA total of 81 patients (86 episodes of IK) were included in this study. All organisms identified were of bacterial origin. Diagnostic yields were similar among direct culture (52.3%), indirect culture (50.8%), and PCR (43.1%; p=0.13). The addition of PCR enabled a positive diagnostic yield in 3 (9.7%) direct culture-negative cases. Based on composite reference standard, direct culture had the highest sensitivity (87.5%; 95% CI, 72.4-95.3%), followed by indirect culture (85.4%; 95% CI, 71.6-93.5%) and PCR (73.5%; 95% CI, 59.0- 84.6%), with 100% specificity noted in all tests. Pairwise comparisons showed substantial agreement among the three tests (percent agreement=81.8-86.2%, Cohen’sk=0.67-0.72). Clinico-microbiological correlation demonstrated higher culture-PCR concordance in cases with greater infection severity.ConclusionsThis study highlights a similar diagnostic performance of direct culture, indirect culture and 16S rRNA PCR for bacterial keratitis, with substantial inter-test concordance. PCR serves as a useful diagnostic adjuvant to culture, particularly in culture- negative cases or those with lesser disease severity (where culture-PCR concordance is lower).
Publisher
Cold Spring Harbor Laboratory