Comparison of In Vivo Confocal Microscopy, PCR and Culture of Corneal Scrapes in the Diagnosis of Acanthamoeba Keratitis

Abstract

All 3 diagnostic tests are highly specific, and a positive test result is highly predictive of disease presence. IVCM is both highly sensitive and specific when performed by an experienced operator. PCR is a useful adjunct in the diagnosis of AK because of its wider availability compared with IVCM, and it may be used in combination with IVCM for microbiologic confirmation.

Acanthamoeba Ocular Infection: Anomalous Presentation of a Potentially Vision-Threatening Condition

“…It has been reported that traditional cultures effectiveness in isolating Acanthamoeba ranges between 30% and 60% [23] and it may take some weeks for final results [24]. Recently newer diagnostic procedures, as IVCM and PCR have been largely adopted, but it was found that they may integrate but not completely substitute amoebic cultures [25,26]. On the other hand, IVCM is a long spending procedure in which any single frame of the scan needs to be evaluated by an expert operator in order to detect lesions that may be related to Acanthamoeba.…”

In vivo confocal microscopy of the inflamed anterior segment: A review of clinical and research applications

“…For example, a recent study showed positive microscopy or culture results for acanthamoeba in 27.1% of laboratory samples, with positive results reported at a mean of 9.4 days . The diagnostic sensitivity of corneal scrape culture in acanthamoeba keratitis is also low (33% [95% CI, 9.9%‐65.1%]) …”

“…Using laser scanning IVCM, Goh et al reported 100% sensitivity and specificity in patients with definite acanthamoeba keratitis (positive IVCM, PCR and/or culture and resolution with treatment) and 88.9% sensitivity and 100% specificity in patients with clinical acanthamoeba keratitis (clinical signs and response to treatment). Fűst et al highlighted the importance of diagnostic criteria, and noted that in cases where bright spots (without or with any of the other three structures) were present in the IVCM, sensitivity was 100% and specificity was 50%.…”

“…31 The diagnostic sensitivity of corneal scrape culture in acanthamoeba keratitis is also low (33% [95% CI, 9.9%-65.1%]). 32…”

Corneal confocal microscopy: ready for prime time

“…The corneal confocal microscope (CCM) is a non‐invasive, ophthalmic imaging modality traditionally used by eye‐care practitioners to diagnose epithelial and stromal abnormalities and acanthamoeba infection . In 2000, a collaboration between ophthalmology departments in Finland (M Rosenberg) and the Netherlands (L Muller) used a tandem scanning confocal microscope on 23 patients with type 1 diabetes, and demonstrated a progressive reduction in corneal nerve fibres with increasing severity of diabetic polyneuropathy…”