Abstract
BackgroundThe tuberculin skin test (TST) identifies individuals at high risk of developing tuberculosis (TB) but poses many challenges. The blood monocyte-to-lymphocyte ratio (MLR) could be an alternative, as extremes in MLR have been associated with increased risk of TB disease.MethodsAt a primary care clinic in Johannesburg, a differential white blood cell count and TST was performed in adults starting antiretroviral treatment (ART) without symptoms suggestive of active TB.ResultsOf 259 participants, 171 had valid results of whom 30% (51/171) were TST positive and the median MLR was 0.18 (IQR 0.13–0.28). The MLR distribution differed between CD4 count categories (p < 0.01), with a broader range of values in TST negative participants with a low CD4 count (≤ 250 cells/mm3), likely reflecting HIV immunosuppression. MLR was associated with a positive TST (OR 0.78 per 0.1 increase, 95% CI 0.59, 0.97) in bivariate analysis but not in multivariate regression analysis (aOR 0.83 for every 0.1 increase, 95% CI 0.60, 1.08).ConclusionIn ART-naïve adults without symptoms suggestive of active TB, MLR was not independently associated with TST positivity and is thus unlikely to be a useful alternative to TST. Future research should focus on development of a cheap, simple and accurate biomarker to identify those people benefiting most from preventive TB therapy.
Highlights
TB remains a global public health threat, with 10 million new tuberculosis (TB) cases and 1.5 million TB deaths annually worldwide [1]
The monocyte-to-lymphocyte ratio (MLR) distribution differed between CD4 count categories (p < 0.01), with a broader range of values in TST negative participants with a low CD4 count ( 250 cells/mm3), likely reflecting HIV immunosuppression
MLR was associated with a positive TST in bivariate analysis but not in multivariate regression analysis
Summary
TB remains a global public health threat, with 10 million new tuberculosis (TB) cases and 1.5 million TB deaths annually worldwide [1]. Among people living with HIV, TB remains an important cause of morbidity and mortality with almost a million TB cases and a quarter million TB deaths in 2018 despite the impressive global roll-out of antiretroviral therapy (ART) [1]. The tuberculin skin test (TST), a surrogate of infection with Mycobacterium tuberculosis, has been widely used to identify people at increased risk of developing TB disease [3]. An important challenge to effective use of either TST or IGRA is the reduced sensitivity in ART-naïve individuals living with HIV due to HIV immunosuppression [7]. The tuberculin skin test (TST) identifies individuals at high risk of developing tuberculosis (TB) but poses many challenges. The blood monocyte-to-lymphocyte ratio (MLR) could be an alternative, as extremes in MLR have been associated with increased risk of TB disease
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