Photo Credit: Tamer Soliman

 The following is a summary of “Microbiological aspects and clinical impact of lower lung field tuberculosis: An observational cohort study in Peru,” published in the January 2025 issue of Infectious Disease by Tan et al. 

Globally, approximately 40% of tuberculosis (TB) cases remain undiagnosed, with Lower lung field (LLF) TB presenting atypically, often misdiagnosed, and contributing to delayed diagnosis, increased transmission, and mortality, particularly in resource-limited settings.  

Researchers conducted a retrospective study to identify microbiological determinants of LLF TB and evaluate treatment responses to optimize care.  

They enrolled adults with microbiologically confirmed pulmonary TB (PTB) diagnosed by GeneXpert MTB/RIF assay or sputum culture in Lima, Peru. Mycobacterium tuberculosis (MTB) lineage was determined through whole-genome sequencing. To address delayed chest radiograph changes in LLF TB, changes in the St. George’s Respiratory Questionnaire (SGRQ) score at the 2-month treatment mark were measured and assessed in World Health Organization-specified final treatment outcomes. Logistic regression was used to evaluate associations between LLF TB, microbiological determinants, and treatment outcomes, while linear regression was applied to analyze variations in SGRQ score changes based on LLF TB status over the first 2 months of treatment.  

The results showed among 1316 patients with PTB, 84 (6%) had LLF TB and patients with LLF TB were more likely to be smear-negative (adjusted odds ratio [aOR] [95% CI] = 2.04 [1.28-3.23], P = 0.002) and infected with Lineage 2 (aOR [95% CI] = 1.95 [1.07-3.41], P = 0.024) compared to patients who were non-LLF TB . People with LLF TB showed less improvement in SGRQ scores after 2 months of treatment (adjusted score difference [95% CI] = –6.29 [–10.99 to –1.59], P = 0.009), but had better final outcomes than patients with non-LLF TB , though this difference was not statistically significant (aOR = 0.43 [95% CI: 0.13-1.05], P = 0.103).  

Investigators concluded that patients with LLF TB, compared to those with upper lung lesions, were more likely to have sputum-negative results on conventional tests, be infected with Lineage 2, and exhibit poorer clinical improvement following treatment. 

Source: sciencedirect.com/science/article/pii/S1201971224003552