A diagnostic method for herpes simplex keratitis by simultaneous measurement of viral DNA and virus-specific secretory IgA in tears: an evaluation

We performed simultaneous measurement of herpes simplex virus (HSV) DNA by real-time polymerase chain reaction (real-time PCR) and of HSV-specific secretory IgA antibody (HSV-sIgA) by enzyme-linked immunosorbent assay (ELISA) in tears obtained using Schirmer strips in order to investigate its diagnostic efficacy for herpes simplex keratitis (HSK). A total of 59 affected eyes from 59 patients with clinically suspected HSK (HSK group) and 23 eyes from 23 healthy volunteers (control group) were enrolled in this study. The HSK group was divided into five subgroups: dendritic/geographic keratitis, disciform keratitis, necrotizing keratitis, atypical keratitis, and others. The tear samples were taken using Schirmer strips to determine the HSV DNA and HSV-sIgA levels. The overall sensitivity and specificity were 55.8 and 100 % for HSV DNA and 49.2 and 82.6 % for HSV-sIgA. The HSV DNA levels in the disciform keratitis subgroup (median, 3.1 x 10(2) copies/sample) were significantly lower than those in the dendritic/geographic keratitis subgroup (median, 2.3 x 10(4) copies/sample) (P < 0.05, Mann-Whitney test). The HSV-sIgA levels in the disciform keratitis subgroup (median, 50.0 NU/ml) were significantly higher than those in the control group (median, 18.0 NU/ml) (P < 0.05, Steel test). The positive and negative predictive values obtained by simultaneous measurement of HSV DNA and sIgA were 90.9 and 61.3 %, respectively. The combination of laboratory detection of HSV DNA by real-time PCR and of HSV-sIgA by ELISA using tear samples enables higher reliability in diagnosing the subgroups of HSK, although the HSV DNA value is relatively lower in disciform HSK than in dendritic/geographic HSK.