C1q Levels: A Reliable Biomarker for Differentiating Active and Latent Tuberculosis Infection.

Background: Tuberculosis (TB) poses a significant public health challenge, particularly because it can exist in an asymptomatic latent phase. Latent TB infection indicates the presence of Mycobacterium tuberculosis without clinical symptoms. Effectively distinguishing between active and latent TB is essential, especially in regions with high TB prevalence, as it may help reduce transmission rates. This study aims to evaluate C1q as a potential biomarker for differentiating active TB from latent forms.

Methods: This prospective cross-sectional study was conducted from January 2017 to February 2018, involving HIV-negative adults aged 18 and older attending TB clinics. Participants were categorized based on clinical symptoms, imaging results, and laboratory tests into active or latent TB. Blood samples were collected to assess serum C1q levels, which were then compared between the two groups.

Results: Out of 81 patients referred for TB evaluation, 38 were diagnosed with active TB. The overall median C1q level was 6.46 μg/ml (interquartile range 4.66-10). The active TB group exhibited significantly elevated C1q levels (10.21 μg/ml) compared to the latent TB group (6.03 μg/ml, P < 0.001). The area under the receiver operating characteristic curve for C1q in distinguishing active from latent TB was 0.74 (95% confidence interval, 0.63-0.85), with sensitivity varying between 61% and 82% at different threshold values.

Conclusions: C1q shows potential as a reliable and easily obtainable biomarker for differentiating active TB from latent infection, demonstrating high sensitivity. These results underscore the need for further research to explore the clinical application of C1q in TB diagnostics.