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PCR analysis of aqueous humour reliably identifies causal pathogens in necrotising retinitis

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Patients with necrotising herpetic retinitis stand a chance of better management with the finding that PCR analysis of aqueous humour can reliably identify the causal pathogen.

The method detected viral DNA in 86% of patients (19/22, 23 eyes) with acute retinal necrosis (ARN) and specifically identified herpes simplex virus (HSV) 1 (two patients) and 2 (four), varicella zoster virus (VZV) (six) and cytomegalovirus (CMV) (four). Three patients with progressive outer retinal necrosis (PORN) all had samples positive for VZV. Among five negative samples, two were positive with repeat samples and in the others antiviral treatment had started before sampling. Samples from controls were all negative for viral DNA.

The investigators recruited 22 patients (29 eyes) with ARN diagnosed according to American Uveitis Society criteria or with PORN. Ten patients with active, non-viral uveitis were the controls. Between 100–150 μl aqueous humour was aspirated from the eyes during an anterior chamber tap on the day of admission. Samples from 22 patients were used in a single PCR to detect herpesvirus DNA and to identify HSV-1, HSV-2, and Epstein-Barr virus (EBV) by restriction analysis of PCR products. Separate assays were performed for CMV and VZV.

Necrotising herpetic retinitis is a condition covering ARN and PORN caused by HSV-1, HSV-2, VZV, CMV, or EBV. Diagnosis is usually clinical but can be uncertain, causing delay in starting the most suitable treatment. Previous work on the diagnostic value of PCR focused on vitreous humour. However, collecting aqueous humour is an easier and safer procedure.