Improving polymerase chain reaction diagnostic rates for herpes simplex keratitis: results of a pilot study

Laboratory confirmation is crucial for diagnosis and management of herpes simplex virus (HSV) keratitis. However, the sensitivity of polymerase chain reaction (PCR) in keratitis is low (25%) compared with that of mucocutaneous disease (75%). We developed an educational intervention aimed at improving the diagnostic yield of PCR.

The medical records of keratitis cases seen at the emergency department of a London tertiary ophthalmic referral hospital over two distinct periods, before and after an educational program on swab technique, were reviewed retrospectively.

A total of 252 HSV cases were included. Increases in the laboratory-confirmed diagnosis of HSV-1 were observed, in both first presentations (11.1%-57.7%) and recurrent cases (20%-57.6%). The rate of positive HSV-1 PCR in eyes with an epithelial defect increased from 19% pre-intervention to 62% post intervention. Notably, 3% were positive for varicella zoster virus DNA, and there was a single case of Acanthamoeba keratitis.

Our results suggest that, with proper swabbing technique, PCR may be more sensitive than previously reported.