Multisite Validation of Cryptococcal Antigen Lateral Flow Assay and Quantification by Laser Thermal Contrast

TLDR

Cryptococcal meningitis is common in sub‑Saharan Africa. The study aimed to evaluate the diagnostic performance of a rapid, point‑of‑care CRAG lateral flow assay in HIV‑infected patients with suspected meningitis. The authors compared CSF culture, CRAG latex agglutination, India ink microscopy, and CRAG LFA across 832 patients in Uganda and South Africa. CRAG LFA demonstrated superior diagnostic accuracy (sensitivity 99.3 %, specificity 99.1 %) compared to culture, latex agglutination, and India ink microscopy, with culture sensitivity increasing with CSF volume, latex test performance varying by manufacturer, and laser thermal contrast achieving 92 % accuracy in quantifying CRAG titers, underscoring CRAG LFA as a major advance for meningitis diagnostics in resource‑limited settings.

Abstract

Abstract Cryptococcal meningitis is common in sub-Saharan Africa. Given the need for data for a rapid, point-of-care cryptococcal antigen (CRAG) lateral flow immunochromatographic assay (LFA), we assessed diagnostic performance of cerebrospinal fluid (CSF) culture, CRAG latex agglutination, India ink microscopy, and CRAG LFA for 832 HIV-infected persons with suspected meningitis during 2006–2009 (n = 299) in Uganda and during 2010–2012 (n = 533) in Uganda and South Africa. CRAG LFA had the best performance (sensitivity 99.3%, specificity 99.1%). Culture sensitivity was dependent on CSF volume (82.4% for 10 μL, 94.2% for 100 μL). CRAG latex agglutination test sensitivity (97.0%–97.8%) and specificity (85.9%–100%) varied between manufacturers. India ink microscopy was 86% sensitive. Laser thermal contrast had 92% accuracy (R = 0.91, p<0.001) in quantifying CRAG titers from 1 LFA strip to within <1.5 dilutions of actual CRAG titers. CRAG LFA is a major advance for meningitis diagnostics in resource-limited settings.