When testing corneal samples for Acanthamoeba keratitis (AK), new research suggests a combination of different PCR assays could better ensure a correct diagnosis compared with culture and a single PCR.

The study, published in the British Journal of Ophthalmology, included 1,217 corneal scraping samples from AK suspected patients.

Sample processing involved both molecular diagnostics and culture. The study used three final point PCR assays using Nelson, ACARNA and JDP1–JDP2 pairs of primers, and two real-time PCR assays using Acant primer-probe.

The researchers reported the estimated prevalence of AK was 1.32%. The sensitivity of Acanthamoeba diagnostic PCRs (73.3% to 86.7%) did not differ significantly from the culture (66.7%), or the target sequence or technology.

Of note: sensitivity could be increased to 93.8% or 100% by combining two or three assays, respectively, the researchers suggested.

The study also found PCR specificity (99.3% to 100%) differed between the assays. Another key finding: T4 was the predominant Acanthamoeba genotype (84.6%).

“Culture and a single PCR assay could lead to misdiagnosing AK. A combination of different PCR assays and improved sample quality could increase diagnosis sensitivity,” the researchers wrote in their paper.

Yera H, Ok V, Kuet FLK, et al. PCR and culture for diagnosis of Acanthamoeba keratitis. Br J Ophthalmol. October 24, 2020. [Epub ahead of print].