CROI 2025 Abstract eBook

Abstract eBook

Poster Abstracts

were transported at 2-8°C to the laboratory and TS results were compared to MGIT. Participant observations on TS feasibility and usability were noted. Results: Valid results on all assays were available from 520 participants for statistical analysis. The median age was 41 years (54% male), 47% were HIV positive and 7% bacteriologically confirmed using MGIT. In comparison to MGIT, test sensitivities for both HCWC and SC TS were 68.3% (95% CI: 51.9%-81.9%), with specificities of 99.4% (95% CI: 98.2%-99.9%) and 99.8% (95% CI: 98.8%- 100%), respectively. Test error rates for the HCWC and SC TS were 21/666 (3.2%) and 23/669 (3.4%), respectively. Most participants (89%) were comfortable with TS collection and confident with self-collection, however participants using XpressCollect™ reported difficulty with collection due to the short swab shaft. Preferences among participants for swab collection were: 149/668 (22%) preferred SC and 230/668 (34%) preferred HCWC, while 289/668 (43%) had no preference. Conclusions: Both HCWC and SC TS showed comparable sensitivity and high specificity compared to MGIT with low error rates, demonstrating that TS is a viable specimen type for TB detection in clinical settings. Majority participants expressed comfort with TS collection and confidence in self-collection, highlighting the acceptability of this method, although swab design was shown to affect usability. The preference data suggests that both self-collection and HCW-collection are suitable options, offering flexibility for patient-centered care. Evaluating the Accuracy of Standard F TB-Feron FIA for TB Infection Diagnosis in Vietnam Han Thi Nguyen 1 , Luan Vo 1 , Andrew Codlin 1 , Tom Wingfield 2 , Rachel Forse 1 , Emily Maclean 3 , Jacob Creswell 4 , Kristi Sidney 1 , Beatrice Kirubi 4 , Hoa Binh Nguyen 5 , Luong Van Dinh 5 , Ha Thu Doan 5 , Lina D. Forsman 1 , for the TBI Testing Team 1 Karolinska Institute, Stockholm, Sweden, 2 Liverpool School of Tropical Medicine, Liverpool, UK, 3 The University of Sydney, Sydney, Australia, 4 Stop TB Partnership, Le Grand-Saconnex, Switzerland, 5 Vietnam National Lung Hospital, Hanoi, Vietnam Background: In Vietnam, national guidelines require a Tuberculosis (TB) infection test before TB preventive therapy can be administered. However, Interferon Gamma Release Assays (IGRAs) require advanced laboratories for processing, resulting in limited access. The Standard F TB-Feron fluorescent immunoassay (TB-Feron) is a simplified IGRA which requires less manual handling and no specialized laboratory staff. Methods: This cross-sectional diagnostic accuracy study was conducted between June and August 2024 and enrolled participants in three groups: 1) people with bacteriologically-confirmed (Bac(+)) pulmonary TB; 2) household contacts (HHCs) of people with TB; and 3) people with a recent negative IGRA test and no known prior exposure to TB. At baseline visits, participants underwent clinical assessment and provided blood for the TB-Feron and QuantiFERON-TB Gold Plus (QFT-Plus) assays, with the latter serving as the TB infection reference standard. Primary endpoints included TB-Feron's sensitivity and specificity. To evaluate secondary endpoints on inter-test agreement and intra-test reproducibility, 15 blood samples were collected and tested with a second TB-Feron assay. Results: We included 345 participants in the analysis, after excluding four with indeterminate TB-Feron and/or QFT-Plus results and two from Group 3 with positive QFT-Plus results. Among the 95 individuals from Group 1 with Bac(+) TB, TB-Feron demonstrated a sensitivity of 88.4% (95% CI: 80.2-94.1). Among 200 HHCs in Group 2, TB-Feron showed a sensitivity of 89.2% (79.8-95.2) and a specificity of 75.4% (66.9-82.6). Among the 50 participants in Group 3 with no prior TB exposure, specificity was 70% (55.4-82.1). Across all groups, TB-Feron's sensitivity and specificity were 90.2% (84.5-94.3) and 73.9% (66.7-80.2), respectively. The concordance between TB-Feron and QFT-Plus was 81% (Cohen’s κ = 0.6167; p<0.001). No systematic differences were observed between the 30 TB-Feron tests performed by two different laboratory staff (Bland Altman plot, p=0.206). Conclusions: This study indicates that TB-Feron has high sensitivity, yet moderate specificity for diagnosing TB infection. Future studies may further evaluate the assay’s diagnostic performance, particularly among key populations, to better understand its potential as a near-point-of-care clinical tool to rapidly indicate TB preventive therapy.

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Diagnostic Accuracy of the FujiLAM Assay to Detect Tuberculosis in Advanced HIV Tessa Adzemovic 1 , Radha Rajasingham 2 , Elizabeth K. Nalintya 3 , Ann M. Fieberg 2 , Emmanuel Mande 1 , George Katende 1 , Spencer Yueh 1 , Olive Namakula 1 , Patricia Nerima 1 , Biyue Dai 2 , David B. Meya 1 , David R. Boulware 2 1 Infectious Diseases Institute, Kampala, Uganda, 2 University of Minnesota, Minneapolis, MN, USA, 3 Makerere University College of Health Sciences, Kampala, Uganda Background: An urgent need exists for non-sputum based point-of-care diagnostics to detect tuberculosis (TB) among people with advanced HIV disease. The Fujifilm SILVAMP TB LAM (FujiLAM) is a novel point-of-care assay that detects mycobacterial lipoarabinomannan (LAM) antigen in urine to identify TB. We present a validation of the updated FujiLAM assay on prospectively collected urine samples from outpatient adults with advanced HIV disease in Uganda. Methods: We performed a prospective diagnostic accuracy study of the FujiLAM TB assay among 617 outpatients with advanced HIV disease at 16 clinics in the Kampala and Wakiso districts of Uganda. We prospectively performed urine Alere LAM testing. Participants with symptoms of TB underwent additional testing including sputum Xpert MTB/Rif (Cepheid, Sunnyvale CA) and sputum culture as per the Ugandan Ministry of Health guidelines. FujiLAM was subsequently run on cryopreserved urine. We determined diagnostic performance for the FujiLAM test against the cases of confirmed TB (defined as Xpert or mycobacterial culture positive) versus negative controls. We additionally assessed the diagnostic performance of the FujiLAM assay for confirmed TB among pre-specified subgroups: people with CD4<100 cells/µL vs. CD4 100-200 cells/µL, antiretroviral therapy (ART) naive vs. ART experienced, and serum C-reactive protein (CRP) <5 mg/L vs. CRP ≥5 mg/L. Results: Overall, we performed FujiLAM testing on 617 participants with Advanced HIV disease. The FujiLAM assay demonstrated 49% (27/55) sensitivity to identify confirmed TB and 97% (172/178) specificity to identify the absence of TB (Figure 1). The positive predictive value was 82%, and negative predictive value was 86%. Among those with CD4 cell counts <100 cells/µL, FujiLAM sensitivity was 61% and specificity was 95%. Among participants with serum CRP >5 mg/L, the FujiLAM assay exhibited a sensitivity of 58% and specificity of 96%. Conclusions: In this diagnostic accuracy study performed on urine samples collected from ambulatory patients with advanced HIV disease in Uganda, the new iteration of the FujiLAM test exhibited moderate sensitivity at 49% and excellent specificity of 97% in identifying confirmed TB. Sensitivity to identify confirmed TB was maximal at 61% in the subgroup of participants with a CD4<100 cells/µL.

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Poster Abstracts

CROI 2025 304