About a third of asymptomatic CrAg-positive patients have concurrent cryptococcal meningitis. More effective clinical assessment strategies and antifungal regimens are required for CrAg-positive patients, including investigation for cryptococcal meningitis irrespective of symptoms. Where it is not possible to perform lumbar punctures in all CrAg-positive patients, blood CrAg titers should be used to target those most at risk of cryptococcal meningitis.

Background: High cryptococcal antigen (CrAg) titers in blood are associated with subclinical meningitis and mortality in CrAg-positive individuals with advanced HIV-disease (AHD). We evaluated a novel semi-quantitative lateral flow assay (LFA), CryptoPS, that may be able to identify individuals with high CrAg titers in a cohort of AHD patients undergoing CrAg screening. Methods: In a prospective cohort of patients with AHD (CD4 ≤200 cells/μL) receiving CD4 count testing, CryptoPS and IMMY LFA CrAg testing were performed on whole blood by two operators blinded to results of the other assay. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of CryptoPS were assessed against IMMY LFA as a reference. CryptoPS low-titer (T1 band) and high-titer (T2 band) results were compared against IMMY LFA titers obtained through serial dilution. Results: 916 specimens were tested. Sensitivity of the CryptoPS assay was 61.0% (25/41, 95% confidence interval [95%CI]: 44.5-75.8), specificity 96.6% (845/875, 95%CI: 95.1-97.7), PPV 45.5% (95%CI: 32.0-59.4), and NPV 98.1% (95%CI: 97.0-98.9). All (16/16) CryptoPS false-negatives were samples with IMMY titers ≤1:160. Of 29 patients (30 specimens) who tested positive on CryptoPS but negative on IMMY LFA, none developed cryptococcal meningitis over 3-months follow-up without fluconazole. Median CrAg titers were 1:20 (interquartile range [IQR] 0-1:160) in CryptoPS T1-positive samples and 1:2560 (IQR 1:1280-1:10240) in T2-positives. Conclusions: Diagnostic accuracy of the CryptoPS assay was sub-optimal in the context of CrAg screening, with poor sensitivity at low CrAg titers. However, the CryptoPS assay reliably detected individuals with high titers associated with poor outcomes.

Treatment of tuberculosis (TB) and HIV co-infections is often complicated by drug-to-drug interactions between anti-mycobacterial and anti-retroviral agents. Rifabutin (RFB) is an alternative to rifampin (RIF) for TB regimens and is recommended for HIV patients concurrently receiving protease inhibitors because of reduced induction of CYP3A4. This study sought to determine the proportion of RFB susceptible isolates among RIF-resistant strains in a high HIV prevalence setting in South Africa. In addition, the study explored the association between rpoB mutations and minimum inhibitory concentrations (MIC) of RIF and RFB. A total of 189 multidrug resistant (MDR) Mycobacterium tuberculosis isolates from the Centre for Tuberculosis repository were analyzed. The MICs were determined using a MYCOTB Sensititre plate method and the rpoB gene was sequenced. Of the 189 MDR isolates, 138 (73%) showed resistance to both RIF and RFB, while 51 (27%) isolates were resistant to RIF but retained susceptibility to RFB. The S531L was the most frequent rpoB point mutation in 105/189 (56%) isolates, followed by H526Y in 27/189 (14%) isolates. Resistance to both RIF and RFB was found predominantly in association with mutations S531L (91/105, 87%), H526Y (20/27, 74%), and H526D (15/19, 79%), while D516V (15/17, 88%), and L533P (3/4, 75%) were found in RIF-resistant, RFB-susceptible isolates. This study has shown that up to 27% of MDR-TB patients in South Africa may benefit from a treatment regimen that includes RFB.

Background: Higher cryptococcal antigen (CrAg) titers are strongly associated with mortality risk in individuals with HIV-associated cryptococcal disease. Rapid tests to quantify CrAg level may provide important prognostic information and enable treatment stratification. Methods: We performed a laboratory-based validation of the semi-quantitative IMMY CrAgSQ assay against the current gold-standard CrAg tests. We assessed diagnostic accuracy of the CrAgSQ in HIV-positive individuals undergoing CrAg screening; determined the relationship between CrAgSQ scores and dilutional CrAg titers; assessed inter-rater reliability; and determined clinical correlates of CrAgSQ scores. Results: A total of 872 plasma samples were tested using both CrAgSQ and conventional IMMY CrAg LFA tests; 692 sequential samples from HIV-positive individuals undergoing CrAg screening and an additional 180 known CrAg-positive plasma samples archived from prior studies. Inter-rater agreement in CrAgSQ reading was excellent (98.17% agreement, Cohen's Kappa 0.962, p<0.001). Using IMMY LFA as a reference standard, CrAgSQ was 93.0% sensitive (95% confidence interval [CI] 80.9%-98.5%) and 93.8% specific (95%CI 91.7%-95.6%). After reclassification of discordant results using CrAg enzyme immunoassay testing, sensitivity was 98.1% (95%CI 90.1%-100%), and specificity 95.8% (95%CI 99.1%- 100%). Median CrAg titers were 1:10 (IQR 1:5-1:20) in the CrAgSQ1+ category; 1:40 (IQR 1:20-1:80) in the CrAgSQ2+ category; 1:640 (IQR 1:160-1:2560) in the CrAgSQ3+ category; and 1:5120 (IQR 1:2560-1:30720) in the CrAgSQ4+ category. Increasing CrAgSQ scores were strongly associated with 10-week mortality. Conclusions: The CrAgSQ test had high sensitivity and specificity compared to the IMMY CrAg LFA test and provided CrAg scores associated with both conventional CrAg titers and clinical outcomes.