Table 1

Results of PCR and immunofluoroscence assay (IFA) versus tissue culture in the tear fluids and corneal scrapings

	Tear fluid^*			Corneal scraping
	Tissue culture			Tissue culture
	Positive	Negative	Total	Positive	Negative	Total
PCR+ve	12 (5.2%)	20 (8.7%)	32 (14%)^†	17 (11.1%)	39 (25.5%)	56 (36.6%)^‡
PCR–ve	00 (0%)	197 (86%)	197 (86%)	00 (0%)	97 (63.4%)	97 (63.4%)
Total	12 (5.2%)^†	217 (94.8%)	229	17 (11.1%)^‡	136 (88.9%)	153

	Sensitivity=100% (–) Specificity=90.7% (86.1 to 94.3) PPV=37.5% (21.1 to 56.3) NPV=100% (–)			Sensitivity=100% (–) Specificity=71.3% (62.9 to 78.7) PPV=30.3% (18.8 to 44.1) NPV=100% (–)

IFA+ve	12 (5.2%)	19 (8.3%)	31 (13.5%)^§	17 (11.1%)	18 (11.8%)	35 (22.9%)^¶
IFA–ve	00 (0%)	198 (86.4%)	198 (86.4%)	00 (0%)	118 (77.1%)	118 (77.1%)
Total	12 (5.2%)^§	217 (94.8%)	229	17 (11.1%)	136 (88.9%)	153

	Sensitivity=100% (–) Specificity=91.2% (86.7 to 94.6) PPV=38.7% (21.8 to 57.8) NPV=100% (–)			Sensitivity=100% (–) Specificity=86.7% (79.9 to 92.0) PPV=48.5% (31.4 to 66.0) NPV=100% (–)

↵* In the 153 patients from whom both tears and scrapings were collected, PCR in tear fluid was positive in 28, that is 18.3% (vs 56 (36.6%) in the corneal scraping; p=0.003, test of proportion), IFA was positive in 26, that is 17% (vs 35 (22.9%) in the corneal scraping; p=0.19, test of proportion), and tissue culture was positive in 11, that is 7.2% of cases (vs 17 (11.1%) in the corneal scraping; p=0.23, test of proportion).
↵† p<0.0005, κ=0.508.
↵‡ p<0.0005, κ=0.356.
↵§ p<0.000, κ=0.522.
↵¶ p<0.0005, κ=0.593.
NPV, negative predictive value; PPV, positive predictive value.