Comparison of tear collection methods for herpes simplex virus type 1 detection via PCR in patients suspected of herpetic stromal keratitis

Mağın M. Comparison of Tear Collection Methods for Herpes Simplex Virus Type 1 Detection via PCR in Patients Suspected of Herpetic Stromal Keratitis. Van Yüzüncü Yıl University Faculty of Medicine, Department of Medical Microbiology, Medical Specialization Thesis, Van, 2025. Herpes simplex keratitis is the leading cause of corneal blindness in developed countries. Herpetic stromal keratitis (HSK), which accounts for 20–61% of recurrent ocular HSV infections, is characterized by HSV type 1 infection of the corneal stroma. This study aimed to compare the diagnostic accuracy of three different tear collection methods—capillary tube, Schirmer strip, and swab—for the detection of HSV-1 DNA via polymerase chain reaction (PCR) in patients clinically suspected of having HSK. Between March 2024 and March 2025, patients with a preliminary diagnosis of HSK referred to the Microbiology Laboratory of Van Yüzüncü Yıl University Dursun Odabaşı Medical Center by the Department of Ophthalmology were enrolled. Simultaneous tear samples were collected using all three methods from a total of 46 patients. HSV-1 presence in all samples was evaluated using a real-time PCR assay. Clinical diagnosis was considered the reference standard. Diagnostic performance— including sensitivity, specificity, and positive predictive value (PPV)—was calculated for each method. Comparative analysis among the sampling techniques was performed using Cochran's Q test, McNemar's test, and Cohen's Kappa statistic. HSV-1 PCR positivity rates were similar across methods: 26.1% for swabs, 23.9% for capillary tubes, and 21.7% for Schirmer strips. Lower positivity rates were observed in patients with prior antiviral treatment. In recurrent cases, especially those sampled with the swab method, higher positivity rates and lower Cq values were noted. Substantial agreement was found between all three methods (Kappa > 0.8). Non-invasive tear collection techniques demonstrated acceptable diagnostic performance in detecting HSV-1 in suspected HSK cases. The swab method may offer superior diagnostic yield in patients with recurrent disease. Prior treatment history and recurrence status may influence PCR test positivity. Keywords: Herpetic Stromal Keratitis; PCR; Tear Sampling; Capillary Tube; Schirmer Strip; Swab Method