Low-volume multiplex solid-phase PCR without DNA extraction for etiological diagnosis of infectious uveitis

To evaluate the usefulness of a low-volume multiplex direct polymerase chain reaction (PCR) in identifying pathogens in intraocular fluid in infectious uveitis.

Prospective interventional non-comparative study.

At a tertiary hospital, the study included 57 participants with active and presumed infectious uveitis and 47 controls (24 active and presumed non-infectious uveitis and 23 non-uveitic conditions). Among the presumed infectious uveitis, there were anterior (38.6%), posterior (19.3%) herpetic uveitis, ocular toxoplasmosis (35.1%), and others (7.0%). Samples (20 µL; 98 aqueous/6 vitreous humors) were analyzed by multiplex direct-strip PCR. It detected six herpesviruses, human T-cell lymphotropic virus (HTLV), Treponema pallidum, and Toxoplasma gondii.

PCR positivity was 35.1%, with detection of herpesviruses [Epstein-Barr virus (EBV), n = 3; cytomegalovirus, n = 2; human herpesvirus 6, n = 2; human herpes virus 1, human herpesvirus 2, varicella zoster virus (VZV), n = 1 for each], T. gondii (n = 9), and T. pallidum and HTLV-I/II in one sample each. All EBV-positive cases had another primary diagnosis (toxoplasmosis or VZV retinitis). Four presumed herpetic infectious uveitis cases turned out to be non-infectious uveitis, including one intraocular lymphoma diagnosis. Presumed posterior herpetic uveitis (n = 3) and ocular syphilis (n = 1) turned out to be ocular toxoplasmosis, whereas one presumed ocular toxoplasmosis turned out to be posterior herpetic uveitis. PCR changed the initial diagnoses in 17.5% of cases. All control samples were PCR-negative.

Direct-strip PCR may contribute to identifying the etiology of infectious uveitis by using limited sample volumes, no DNA extraction step, with rapid results and testing simultaneously for multiple pathogens.