Improved Polymerase Chain Reaction Diagnostic Rates Of Herpes Simplex Keratitis Following An Educational Programme.

Herpes simplex virus (HSV) keratitis is the primary cause of corneal blindness in high income countries and a leading cause of blindness worldwide. Diagnostic uncertainty of HSV keratitis remains a challenge for clinicians. Laboratory confirmation is crucial for diagnosis and management planning. However, the sensitivity of polymerase chain reaction (PCR) in keratitis is low (25%) compared to that of mucocutaneous disease (75%). This study examines the efficacy of an educational intervention to optimise the diagnostic yield of PCR.

This study was conducted within the Emergency Department at Moorfields Eye Hospital NHS Foundation Trust, a tertiary ophthalmic referral hospital in London, UK.

A retrospective review of 252 HSV keratitis cases was undertaken over two distinct periods, before and after an educational programme on swab technique. The educational interventions included lectures for all clinicians in the department on HSV keratitis that highlighted the importance of taking a swab sample for all presentations and, reinforcing the need to debride the epithelium when taking a swab. There was no change in the laboratory testing techniques between the study time points. Consecutive patients with a coded discharge diagnosis of herpes simplex keratitis were identified via electronic patient records. Rapid nucleic acid amplification testing (NAAT) using PCR was performed on initial presentation for HSV-1, HSV-2 and VZV DNA. 

Increases in the laboratory confirmed diagnosis of HSV-1 were observed, in both first presentations (11.1% to 57.7%) and recurrent cases (20% to 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 VZV DNA and there was one case of Acanthamoeba.

The observed improvements in HSV PCR diagnosis in our study may be attributed to the introduction of an educational programme. The results highlight that with a simple, low-cost intervention, PCR diagnosis of HSV keratitis may be more sensitive than previously reported.​ The results imply that education on correct corneal swab techniques, with an emphasis on debridement being beneficial therapeutically and diagnostically, may result in improved diagnosis for both first and recurrent cases of HSV and VZV keratitis. Our study demonstrates it is best practice to confirm all suspected cases of HSV keratitis with PCR.