Effectiveness of real-time PCR for diagnosis and prognosis of varicella-zoster virus keratitis

To determine the efficacy of real-time PCR for the diagnosis and prognosis of varicella-zoster virus (VZV) keratitis. Retrospective case series. Patients: 545 consecutive patients with keratitis were examined to quantify copy numbers of VZV DNA by real-time PCR. Association of copy numbers of VZV DNA to clinical signs and disease course was assessed by logistic regression analysis and Cox proportional hazard model. Of the 545 eyes, 38 (6.9%) were diagnosed as VZV keratitis. The median copy number of the VZV DNA was 10(4.19) copies; this number was significantly associated with diagnosis of VZV keratitis with the highest odds ratio of 3390 (for median copy) compared to the clinical signs. The diagnostic accuracy of the VZV DNA copy indicated good diagnostic value of area under the curve (0.92) by receiver operating characteristic analysis, and detection of unrelated VZV DNA from the cornea was very rare (0.2%). When the VZV DNA copy and clinical signs were assessed for association with the disease course of herpes zoster ophthalmicus, the disease duration was significantly prolonged in VZV keratitis cases with higher numbers of VZV DNA copies, iritis, and history of recurrences. The amount of VZV DNA led to a continuous risk of prolonged disease duration until the ocular inflammation subsided (hazard ratio 0.17, 95% CI 0.07-0.42, for median copies). Higher VZV DNA copy numbers are associated with the refractoriness of VZV keratitis, and its evaluation may be a useful way to clinically diagnose and manage VZV keratitis.