neoformanswas identified in 9 and 5 subjects, respectively, by culture or was documented at outside hospitals. (LA) tests (15) and has demonstrated good individual sensitivity for the capsular polysaccharide glucuronoxylomannan (GXM) of all fourC. neoformansserotypes (6). However , most comparative studies have relied primarily on samples from HIV patients (1, 2, 79), so little is known about the relative performance of CrAg LFA in HIV-negative individuals, in whom fungal burden may be lower. The present study aimed to evaluate the sensitivity of CrAg LFA in diagnosing cryptococcosis in HIV-negative adults. (This work was presented in part at the 115th General Meeting of the American Society for Microbiology, New Orleans, LA, 30 May to 2 June 2015. ) We first conducted a validation of the CrAg LFA assay using 36 frozen archival serum samples (26 positive/10 negative) and 23 cerebrospinal fluid (CSF) specimens (13 positive/10 negative) that were previously tested in the laboratory by LA (CALAS; Meridian Bioscience Inc., Cincinnati, OH). This was performed on archived specimens gathered from patients on an Institutional Review Board (IRB)-approved clinical protocol. Retesting of these Lesinurad specimens by qualitative and semiquantitative CrAg LFA demonstrated 100% agreement with previously tested LA-positive and LA-negative samples in this set. The relative limits of detection of LA and LFA were then tested in two Lesinurad experiments in which serum and CSF specimens were serially diluted to final negative titers for the two assays tested in parallel. The LFA assay remained positive at substantially greater dilutions than the LA assay did for the tested specimens: Final titers (LFA versus LA) were 1: 8, 192 versus 1: 512 for serum and 1: 8, 192 versus 1: 128 for CSF, which is consistent with a lower limit of detection for the LFA assay for the two specimen types. Following validation, the qualitative and semiquantitative CrAg LFA assays were performed on archived specimens collected from HIV-negative individuals with confirmed diagnoses of cryptococcosis. To challenge the limits of sensitivity of the LFA assay, specimens were selected that had tested negative by EIA, potentially reflecting lower antigen titers. All but four of these samples tested positive by LA. Statistical analysis of LFA results was performed with Prism version 6. 0 (GraphPad Software, Inc. ), and all values are expressed herein as mean plus or minus standard deviation (SD) or median (minimum, maximum) for continuous variables and as frequencies for categorical variables. LA and LFA titers were log-transformed for analysis. The Spearman rank correlation coefficient (rS) was used to analyze a correlation between the ln LA titer and the ln LFA titer. The Bland-Altman plot was used to analyze the correlation between the ln LA titer and the ln LFA titer (10). CrAg LFA titers were performed on 51 serum and 9 CSF samples from 31 patients. Seventeen subjects were male, and the mean age was 48 13 years. Coexisting immunodeficiency conditions were idiopathic CD4+lymphopenia (6/31), anti-granulocyte-macrophage colony-stimulating factor (GM-CSF) antibody (4/31), Good syndrome (1/31), STAT 1 mutation (1/31), T-cell lymphoma (1/31), and myasthenia gravis (1/31). Other underlying diseases (some patients had multiple) were hypertension (9/31), hypothyroidism (2/31), diabetes mellitus (1/31), chronic kidney disease (1/31), and chronic hepatitis B (1/31). Nine patients (29%) had unknown underling diseases. Sites of cryptococcal infection were the central nervous system (20/31), lungs (7/31), and disseminated infection (4/31). C. gattiiandC. neoformanswas identified in 9 and 5 subjects, respectively, by culture or was documented at outside hospitals. The other 17 subjects had a clinical diagnosis with a positive cryptococcal antigen or pathological diagnosis of cryptococcosis but had negative cultures in our institution. The species ofCryptococcusin these 17 cases was unknown to the investigators in Col13a1 the present study. All samples were positive by CrAg LFA (100% sensitivity; 95% confidence interval (CI), 92% to 100% for serum; 95% CI, 66% to 100% for CSF). CrAg LFA titers and LA titers ranged from <1: 2 to 1: 5, 120 and 1: 2 to 1: 1, 024, respectively (Table 1), and CrAg LFA titers were greater than LA titers in almost all Lesinurad cases. The Spearman rank correlation coefficient (rS) between ln LA and ln LFA titers was 0. 79 (95% CI, 0. 66 to 0. 88; P < 0. 0001) (Fig. 1). The Bland-Altman plot showed a bias of 1. 9 (SD,.