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Daisuke Shimizu, Dai Miyazaki, Keiko Yakura, Tomoko Haruki, Yoshitsugu Inoue; Evaluation of effectiveness of real-time PCR for bacterial keratitis diagnosis. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4061.
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To determine the effectiveness of measurement of bacterial DNA amount by real-time PCR for the diagnosis of bacterial keratitis, we characterized the sensitivity and specificity profile and determined cut-off value for diagnosis by using Receiver Operating Characteristic (ROC) analysis.
Consecutive case series (241 eyes of 241 cases), suspected of infectious keratitis and measured for the amount of bacterial DNA in corneal tissue samples, were retrospectively analyzed. The measurement of bacterial DNA amount (16S rDNA by real-time PCR), smear examination by Gram and<br /> Fungiflora staining, and culture testing were evaluated for diagnostic efficacy by ROC analysis.
One hundred and nine eyes were diagnosed as definitive bacterial keratitis. Eighty four eyes were diagnosed as keratitis of other causes. In the definitive bacterial keratitis eyes, average bacterial DNA copy number was 1.6x106, culture positive rate was 54%, and the smear positive rate was 45%. In the non bacterial keratitis eyes, they were 6.1x103, 0.0%, and 7.0%, respectively. Area under the curve (AUC) was calculated to show diagnostic efficacy based on ROC analysis of these testing. The AUC for definitive bacterial keratitis was 0.73, 0.65, and 0.60 for smear testing, bacterial DNA copy measurement, and culture testing, respectively. To determine the most useful combination of each testing, AUC of combined outcome was calculated using propensity scoring analysis. Combination of smear testing and bacterial DNA amount indicated highly efficacious diagnostic value (AUC: 0.80), and cut off value of bacterial DNA copy for diagnosis of bacterial keratitis was 1.0X103.
Combined testing of bacterial DNA quantification and smear testing was highly efficacious to definitively diagnose bacterial keratitis at initial visit.
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