Laboratory methods in the detection of herpes simplex virus (HSV) in keratitis--a 9-year study including polymerase chain reaction (PCR) during last 4 years.

Conventional methods of fluorescent antibody test (FAT) and virus isolation (VI) and molecular method of polymerase chain reaction (PCR) were compared for the detection of HSV in keratitis during a 9-year period. Of 186 corneal scraping specimens, 108 were subjected to FATand VI in the pre-PCR period (initial 5 years) while 78 to FAT, VI and PCR in the PCR period (latter 4 years). HSV was detected by FAT in 44/186 (23.7%), VI in 18/186 (9.7%) and PCR in 27/78 (34.6%) specimens. Overall, HSV was diagnosed in 56/186 (30.1%) specimens. PCR has increased the clinical sensitivity by 12.8%, which is statistically significant (McNemar test, P-0.002). VI should be replaced by PCR. FAT though less sensitive should always be employed as a routine to give an early diagnosis, the results of which could be further confirmed, if necessary, by PCR, which is a more sensitive and specific diagnostic tool.