# Markers of pulmonary TB in care-seeking patients with respiratory symptoms

## TL;DR

This study identifies clinical and lab markers that help diagnose pulmonary TB in patients with respiratory symptoms, especially in high-prevalence areas.

## Contribution

The study comprehensively evaluates sociodemographic, radiographic, and biological factors associated with pulmonary TB using standardized tools in a high-prevalence setting.

## Key findings

- Cavitation on chest X-ray is strongly associated with pulmonary TB diagnosis.
- High alkaline phosphatase and elevated C-reactive protein levels are significant biomarkers for PTB.
- Major depression disorder shows a protective association with PTB.

## Abstract

To appropriately triage and evaluate people with signs or symptoms of pulmonary TB, clinical, laboratory, and radiological variables, as well as biomarkers, have been prioritised to increase early detection. However, in high TB prevalence areas, few studies used standardised tools to assess both sociodemographic characteristics and accessible biomarkers comprehensively. This study aimed to describe the sociodemographic, radiographic, clinical, and laboratory characteristics associated with pulmonary TB (PTB) in patients with presumed pulmonary TB (pPTB).

A cross-sectional study was conducted at a public health centre in Duque de Caxias, Brazil, involving patients with pPTB from September 2017 to February 2020. Participants were evaluated using standardised tools: Patient Health Questionnaire 9 (PHQ-9) and the Mini International Neuropsychiatric Interview (MINI) Plus for depression, the MINI-Mental State Examination for cognitive functions, and the ASSIST (Alcohol, Smoking, and Substance Involvement Screening Test) questionnaire for substance use. Chest radiographs (CXRs) and blood tests were also performed. Logistic regression was used to identify associations between sociodemographic, radiographic and biological variables with PTB.

Of 315 patients, 149 (47%) were diagnosed with PTB. Factors associated with PTB included the presence of cavitation on CXR (OR 13.7, 95% CI 5.93–34.5; P < 0.001), high alkaline phosphatase levels (OR 3.89; 95% CI 1.68–9.47; P = 0.002), and C-reactive protein above 10 mg/L (OR 5.60, 95% CI 2.23–14.7; P < 0.001). Major depression disorder (OR 0.33, 95% CI 0.11–0.91; P = 0.036) suggested a protective association with PTB.

CXR findings and easy-to-perform blood tests can aid in PTB diagnosis, potentially reducing the time to treatment when microbiological or molecular tests cannot be performed.