Factors associated with pulmonary tuberculosis in LTBI individuals screened from close contacts: a retrospective...

Latent tuberculosis infection (LTBI) progresses to pulmonary tuberculosis (PTB) in 5-10% of cases. This study aimed to identify factors associated with PTB among close contacts of PTB patients and to develop an exploratory nomogram for individualized risk estimation.

A retrospective case-control study was conducted in Henan Province, China, in 2024. The PTB group comprised newly diagnosed PTB patients (n = 365), and the LTBI group comprised close contacts of PTB patients who tested positive on the purified protein derivative (PPD) test, with normal chest imaging and no clinical evidence of active TB after physician evaluation (n = 389). Participants were randomly divided into a training set (70%, n = 528) and a validation set (30%, n = 226). Multivariable logistic regression was performed to identify factors associated with PTB. An exploratory nomogram was developed based on the independent factors and internally validated using bootstrap resampling (1,000 replicates). Model performance was assessed using the area under the receiver operating characteristic (ROC) curve, calibration curves, and decision curve analysis (DCA).

Nine factors were independently associated with PTB. Factors associated with increased risk included age ≥60 years (OR = 2.261), male gender (OR = 3.587), diabetes (OR = 3.779), underweight (OR = 5.312), and self-reported high stress (OR = 1.862). Factors associated with decreased risk included married status (OR = 0.187), certain occupations (e.g., farmers, students), overweight (OR = 0.393), obesity (OR = 0.124), receipt of TB health education (OR = 0.446), and presence of a BCG scar (OR = 0.497). The exploratory nomogram showed AUCs of 0.842 (95% CI: 0.809-0.874) in the training set and 0.833 (95% CI: 0.780-0.885) in the validation set. Calibration curves demonstrated good agreement, and DCA suggested potential clinical utility.

Age ≥60 years, male gender, diabetes, underweight, and high stress were associated with increased PTB risk, while married status, certain occupations, overweight, obesity, TB health education, and BCG scar were associated with decreased PTB risk among close contacts. The exploratory nomogram showed good discriminative ability in internal validation but requires external validation before clinical application.