In Blantyre, Malawi, 17.4% of 2895 adolescents and adults aged 10-40 years had positive QuantiFERON-TB Gold Plus responses.

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medRxiv Published April 10, 2026 Medically reviewed April 25, 2026 Study authors: Phiri, M. D.; Rickman, H. M.; Mandalasi, C.; Chirambo, A.; Jambo, K. C.; Mwandumba, H. C.; Corbett, … DOI ↗ By Dr. Amelia Tan, PhD · Internal Medicine & Chronic Disease

Key Takeaway

Note that in Blantyre, Malawi, 17.4% of 2895 adolescents and adults had positive QFT-Plus responses; TB2-TB1 differential >0.6 IU/mL occurred in 3.8%.

This community-based survey evaluated quantitative interferon gamma responses to Mycobacterium tuberculosis using the QuantiFERON-TB Gold Plus (QFT-Plus) assay in 2895 adolescents and adults aged 10-40 years in Blantyre, Malawi. The study examined the probability of positive responses, response magnitude, and associated factors, including the effect of hypothetical alternative positivity thresholds on inferences regarding age- and sex-specific transmission patterns.

At the standard QFT-Plus positivity threshold of 0.35 IU/mL, 17.4% of participants (503 of 2895) demonstrated a positive TB1 or TB2 response. Additionally, 3.8% of participants (109 of 2895) exhibited a TB2-TB1 differential greater than 0.6 IU/mL. Analysis indicated that a TB2-TB1 differential exceeding 0.6 IU/mL was associated with reduced odds of HIV, with an adjusted odds ratio of 0.37 (95% CI 0.14-0.93).

Predicted Mtb immunoreactivity prevalence ratios were calculated for males versus females at age 19 years. At a hypothetical 0.1 IU/mL threshold, the prevalence ratio was 0.90 (95% CI 0.83-0.99), indicating lower predicted immunoreactivity in males. At a 0.5 IU/mL threshold, the prevalence ratio was 1.02 (95% CI 0.89-1.15). No adverse events, serious adverse events, discontinuations, or tolerability data were reported for this diagnostic assay.

Key limitations include the observational study design and lack of reported follow-up, which preclude causal inferences regarding clinical outcomes. In high-burden settings, these quantitative IGRA responses may help clarify Mtb transmission patterns and guide targeted public health strategies, though results must be interpreted within the context of survey data.

Study Details

Sample sizen = 2,895

EvidenceLevel 5

PublishedApr 2026

View Original Abstract ↓

Background: Binary interpretation of Mycobacterium tuberculosis (Mtb) interferon gamma release assay (IGRA) results discards information about recency of exposure and disease risk. We analysed quantitative IGRA responses to Mtb in a community--based survey to investigate associations with response magnitude and inform understanding of transmission dynamics. Methods: We included QuantiFERON--TB Gold Plus (QFT--Plus) results from 2,895 participants (10--40 years old) in Blantyre, Malawi. Bayesian regression models assessed the probability of a positive response ([≥]0.35 IU/mL), response magnitude, and associated factors. We also investigated associations with a TB2-TB1 differential >0.6 IU/mL (proposed to reflect recent transmission), and how hypothetical alternative IGRA positivity thresholds affected inference about age-- and sex--specific transmission. Results: 17.4% (503/2,895) of participants had positive TB1 or TB2 responses at the QFT--Plus positivity threshold (0.35 IU/mL). The distributions of TB1 and TB2 responses, among participants with positive QFT--Plus, were similar across age and sex. A TB2-TB1 differential >0.6 IU/mL occurred in 3.8% (109/2,895) of participants and was not associated with age or sex. However, participants with HIV had reduced odds of TB2-TB1>0.6 IU/mL (adjusted odds ratio 0.37 [0.14--0.93]). At higher hypothetical positivity thresholds, the mean predicted Mtb immunoreactivity prevalence among males exceeded that in females at an earlier age: at 19 years, predicted immunoreactivity prevalence ratios were 0.90 (0.83--0.99) and 1.02 (0.89--1.15) at 0.1 IU/mL and 0.5 IU/mL thresholds, respectively. Conclusions: Quantitative IGRA responses offer information about age-- and sex--specific immunoreactivity and transmission risks that dichotomisation obscures. In high-burden settings, quantitative IGRA responses may clarify Mtb transmission patterns and guide targeted public health strategies.

In Blantyre, Malawi, 17.4% of 2895 adolescents and adults aged 10-40 years had positive QuantiFERON-TB Gold Plus responses.

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In Blantyre, Malawi, 17.4% of 2895 adolescents and adults aged 10-40 years had positive QuantiFERON-TB Gold Plus responses.

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