CROI 2020 Abstract eBook

Abstract eBook

Poster Abstracts

743 DIAGNOSTIC PERFORMANCE OF A SEMIQUANTITATIVE POINT-OF-CARE ASSAY FOR CRYPTOCOCCOSIS Tadeo K. Kiiza 1 , Audrey Nimwesiga 1 , Caleb P.Skipper 2 , Richard Kwizera 1 , Lucy Apeduno 1 , Michael Okirwoth 1 , John Bosco Kafufu 1 , Elizabeth Nalintya 1 , Darlisha A.Williams 2 , Joshua Rhein 2 , David B. Meya 1 , David R. Boulware 2 1 Infectious Diseases Institute, Kampala, Uganda, 2 University of Minnesota, Minneapolis, MN, USA Background: Blood Cryptococcal Antigen (CrAg) titer is associated with risk of cryptococcal meningitis. We describe the diagnostic performance of a novel all-in-one CrAg semi-quantitative (SQ) lateral flow assay (LFA) compared to the FDA-approved Immy CrAg LFA in the rapid diagnosis of cryptococcosis. The CrAg SQ LFA provides a semi quantitative test result in a single test in contrast to traditional semi-quantitative testing which requires serial dilutions and multiple tests. Methods: From February to September 2019, we compared the diagnostic performance of the CrAg SQ assay (Immy) with the CrAg LFA (Immy) on 100 CSF samples, 61 serum samples collected from HIV+ persons with meningitis and 50 serum samples from HIV+ persons with CD4<100 screened for cryptococcal antigenemia. The CrAg SQ levels (1+ to 4+) were compared with CrAg LFA titers to determine the corresponding cut off CrAg SQ titer. All specimens were prospectively tested. Results: Among meningitis patients, 69 had cryptococcal meningitis (68 CrAg+ by LFA and 1 false negative due to prozone with 1:1310720 CrAg LFA titer), and 31 had no cryptococcal meningitis by CrAg, culture, and India ink. The CrAg SQ on CSF had 100% (69/69) sensitivity and 100% specificity (31/31) when prospectively run on fresh specimens. CSF CrAg titers detected ranged from 1:2 to 1:209715520. In serum, sensitivity was 100% (46/46) and specificity 100% (15/15) among meningitis patients. Using serum in asymptomatic patients, CrAg SQ had 100% sensitivity (13/13) and 97.4% (37/38) specificity with one CrAg SQ being trace 1+ positive. Among all specimen types, the overall CrAg SQ sensitivity was 100% (128/128) and specificity was 99% (83/84); (P=0.99 by McNemar). Overall, CrAg SQ levels from 1+ to 5+ corresponded to increasing CrAg LFA titers (Figure). CSF CrAg SQ results of 3+ or higher were always CSF culture positive. Conclusion: The CrAg SQ LFA appears to be an excellent semi-quantitative CrAg assay maintaining both sensitivity and specificity, with rapid stratification of patient risk. Training laboratory personnel on the usage and interpretation of the CrAg SQ is necessary.

for this neglected disease. For tuberculosis, the FDA recognizes an official surrogate endpoint as “time to sputum culture conversion to negative.” We examined the relationship between the rate of CSF Cryptococcus clearance (i.e. EFA) and mortality through 18 weeks. Methods: We pooled individual-level CSF data from 3 sequential cryptococcal meningitis clinical trials conducted in Uganda during 2010-2013 (COAT trial, n=162; also in South Africa), 2013-2014 (ASTRO-CM pilot, n=179), and 2015-2019 (ASTRO-CM trial, n=397). All subjects received amphotericin B deoxycholate + fluconazole induction therapy and had serial quantitative CSF cultures performed. The log 10 transformed colony forming units (CFUs) per mL CSF were analyzed by general linear regression vs day of CSF culture over the first 10 days. The slope of the fit line is the EFA or the rate of CSF fungal clearance in units of log 10 CFU/mL/day. We grouped subjects by EFA and compared mortality by Kaplan-Meier. Results: 738 subjects had non-sterile initial cultures with a calculable EFA (median 0.38; IQR, 0.20-0.57 log 10 CFU/mL). Risk of death through 18-weeks was higher with EFA <0.20 (50%mortality) versus EFA >=0.20 log 10 CFU/ml/ day (37%mortality; Hazard Ratio 1.60; 95%CI, 1.25 to 2.04; P=0.002). Mortality through 18-weeks was 37% for EFA ≥0.60 (n=170), 36% for EFA 0.40-0.59 (n=182), 39% for EFA 0.30-0.39 (n=112), and 35% for EFA 0.2-0.29 (n=87). When adjusting for baseline Glasgow coma scale, hemoglobin, CSF quantitative culture, CSF WBC, biological sex, and cohort, EFA remained significant (adjusted Hazard Ratio 1.83, 95%CI, 1.40 to 2.40; P<0.0001). Conclusion: EFA was associated with all-cause mortality using individual level data from 738 subjects receiving amphotericin-combination induction therapy. An EFA better than 0.20 log 10 CFU/mL/day was associated with similar survival, and this threshold may be considered a target for a surrogate endpoint. Yet, 25% of patients receiving amphotericin had EFAs worse than 0.20 log 10 CFU/mL/ day, with 50%mortality. This builds upon prior systematic reviews of smaller pooled studies from different sites to validate EFA as a surrogate endpoint.

Poster Abstracts

745 EVALUATING THE IMMY SEMI-QUANTITATIVE CrAg LFA IN HIV-POSITIVE PATIENTS IN BOTSWANA Kwana Lechiile 1 , Mark W. Tenforde 2 , Thandi Milton 3 , Amber Boose 3 , Tshepo B. Leeme 1 , Leabaneng Tawe 3 , Charles Muthoga 3 , Fredah Mulenga 1 , Ikanyeng Rulaganyang 3 , Julia Ngidi 4 , Madisa Mine 4 , Joseph N. Jarvis 5 1 Botswana Harvard AIDS Institute Partnership, Gabarone, Botswana, 2 University of Washington, Seattle, WA, USA, 3 Botswana–UPenn Partnership, Gaborone, Botswana, 4 National Health Laboratory, Gaborone, Botswana, 5 London School of Hygiene & Tropical Medicine, London, UK Background: Cryptococcal antigen (CrAg) titers are an important prognostic indicator in HIV-positive patients with cryptococcal infection and could potentially be used to stratify treatment. Current titration methods are expensive and labor intensive. A novel semi-quantitative (SQ) CrAg test has been developed that can provide an indication of CrAg titer using a simple dipstick lateral flow assay (LFA). We performed a study to evaluate the performance of the SQ-CrAg assay against the standard CrAg LFA in patients with HIV-associated cryptococcal infection in Gaborone. Methods: Residual EDTA blood specimens from sequential HIV-positive patients undergoing routine CD4 testing with CD4 counts of ≤200 cells/ml were screened through the reflex CrAg-screening program in Botswana using both

744 EARLY FUNGICIDAL ACTIVITY AS SURROGATE ENDPOINT FOR CRYPTOCOCCAL MENINGITIS SURVIVAL

David R. Boulware 1 , Matt Pullen 1 , Katherine Huppler Hullsiek 1 , Joshua Rhein 1 , Lillian Tugume 2 , Edwin Nuwagira 3 , Kenneth Ssebambulidde 2 , Mahsa Abassi 1 , Radha Rajasingham 1 , Katelyn Pastick 1 , Caleb P. Skipper 1 , Abdu Musubire 2 , Conrad Muzoora 3 , David Meya 2 , for the ASTRO-CM Team 1 University of Minnesota, Minneapolis, MN, USA, 2 Infectious Disease Institute, Kampala, Uganda, 3 Mbarara University of Science and Technology, Mbarara, Uganda Background: In cryptococcal meningitis phase 2 clinical trials, early fungicidal activity (EFA) of Cryptococcus yeast clearance from cerebrospinal fluid (CSF) is used as a surrogate endpoint. The US FDA allows for surrogate endpoints for accelerated regulatory approval, but there are no accepted surrogate endpoints

CROI 2020 274