BACKGROUND:The DiaSorin LIAISON® QuantiFERON-TB Gold Plus test offers automation advantages over the standard QIAGEN ELISA; however, data comparing the two methods in pregnant women are lacking. We assessed the categorical and quantitative agreement between these interferon-gamma release assay platforms for latent tuberculosis infection (LTBI) detection in a cohort of pregnant women in Uganda.
METHODS:In this cross-sectional diagnostic comparison, 261 pregnant women were enrolled at Kawempe National Referral Hospital in Kampala, Uganda (September-December 2020). Plasma samples were initially tested with QIAGEN ELISA (QFT-ELISA) in 2021, stored at -80°C, and retested in 2025 with both LIAISON® chemiluminescent immunoassay (QFT-CLIA) and QFT-ELISA. Agreement was assessed using Cohen's kappa, Bland-Altman analysis, and Deming regression analyses. Stability over four years was evaluated using weighted kappa and transition analyses. Subgroup analyses examined agreement by HIV status and trimester RESULTS: Of the 261 enrolled participants, 231 samples (88.5 %) remained viable after four years storage. Overall agreement between QFT-CLIA and QFT-ELISA in 2025 was 90.5 % (Cohen's Kappa 0.82; 95 % CI: 0.75-0.89). Bland-Altman analysis showed minimal systematic bias (mean difference for TB1-Nil: +0.046 IU/mL, p = 0.608, TB2 Nil: +0.0776 IU/mL, p = 0.3175), and Deming regression confirmed linearity (slope, 0.94-0.96). Among the 187 samples that remained QFT-stable between 2021 and 2025, the agreement improved to 98.4 % (kappa 0.97; 95 % CI: 0.94-1.00), with category-specific agreement of 93.6 %, 97.5 %, and 100 % for positive, negative, and indeterminate results, respectively. Four-year stability varied according to baseline classification: 57.1 % for positive samples, 97.5 % for negative samples, and 75.0 % for indeterminate samples. Agreement was similar between HIV-positive (84.6 %, Kappa 0.76) and HIV-negative participants (90.8 %, Kappa 0.82; p = 0.357).
CONCLUSIONS:The LIAISON® platform demonstrated excellent agreement with the QIAGEN ELISA for LTBI detection during pregnancy, particularly when storage effects were minimized. Long-term cryopreservation disproportionately affects positive samples. The automation of the LIAISON® platform supports high-throughput implementation in antenatal care settings; however, fresh sample testing should be prioritized for clinical decision-making.