Dedicated PCR Infection Panel to Speed Up Diagnosis

Ophthalmology needs a dedicated polymerase chain reaction (PCR) panel, according to Madhavan Rajan MD.

Noting it as a vexing gap in technology for ophthalmologists, he said the materials required to create such a dedicated PCR panel are available, yet demand remains unmet.

“Presently, for the diagnosis of infections such as vision-threatening keratitis, the detection of an organism requires multiple scrapes and multiple microbial investigations. This process can take days, causing delayed diagnosis,” Professor Rajan said.

“We do not have a panel for ophthalmology. We do not have a PCR panel [capable of] detecting the most common ocular pathogens.”

Prof Rajan presented his intended solution: the iCAM test. It’s a single-sample test involving a corneal epithelial scrape with the capacity to screen for multiple ocular pathogens.

The iCAM project involves multiple experts on molecular diagnostics at the universities of Cambridge and Anglia Ruskin in England, including PCR specialists, microbiologists, and clinicians. The team developed the iCAM test using data spanning more than two decades as part of their research.

Thermo Fisher Scientific constructed the panel the team created, and it features 96 targets specific to ophthalmology, including bacteria, viruses, fungi, and Acanthamoeba. It also included positive controls, human genome regulatory single-nucleotide variant predictors, MRSA, microsporidia, and toxoplasmosis and histoplasma.

The iCAM was then subjected to internal quality control using external quality assessment panels and synthetic plasmid controls. Samples were processed within 4 to 5 hours “in the best situation,” and all were complete in less than 20 hours.

A subsequent clinical trial involved 34 patients with acute infective keratitis, with two samples taken from each: one for conventional microbial scraping and another for the iCAM.

Prof Rajan reported the iCAM was equally effective as conventional microbial testing, with better sensitivity for Acanthamoeba and fungal organisms. The sample reporting time was less than 24 hours for all iCAM tests—much faster than conventional testing.

The iCAM, he said, promises to fill the gap in rapid diagnostics for acute, sight-threatening keratitis, adding it will also help doctors institute the “proper antimicrobial as fast as possible” and aid in avoiding polypharmacy.

“We have heard from other speakers around the globe [how] the detection rate [of keratitis] still lingers around 50% in even the best situations. The iCAM panel could increase this rate to 80% and make it very easy to identify multiple causative organisms as in polymicrobial keratitis,” Prof Rajan said.

“If there are co-infections, [the test] would also be able to pick up Acanthamoeba together with fungi within about 4 to 5 hours. This compares to waiting for days before unravelling this type of mystery.”

Prof Rajan presented at the 2025 EuCornea congress in Prague.

Madhavan Rajan MBBS, MS, MD, FRCSEd, FRCS(Glas), FRCOphth is a Consultant Ophthalmologist and Clinical Lead for the Cornea and Cataract service at Cambridge University Hospitals and Clinical Academic at University of Cambridge and Anglia Ruskin University, UK. madhavan.rajan1@nhs.net