Pre-treatment chest X-ray stability duration and tuberculosis disease in San Diego, California, 2012–2017

BACKGROUND: Overseas screening for tuberculosis (TB) has sought to reduce the burden of active TB in the United States. The duration of time between two unchanged, or stable, chest X-rays (CXRs) taken four to six months apart has been considered clinically useful in the evaluation of suspected pulmonary TB disease, but this relationship has not been previously quantified. OBJECTIVE: To investigate the association between pre-treatment CXR stability duration and future clinical or culture-confirmed (Class 3) diagnosis of pulmonary TB in San Diego, California, USA. METHODS: This retrospective record review included County of San Diego TB clinic patients with abnormal CXR results who were started on treatment between 2012 and 2017; multivariable logistic regression was used to analyze the clinical data. RESULTS: Pre-treatment CXR stability duration of at least four months was not significantly associated with a Class 3 pulmonary TB diagnosis (adjusted odds ratio [AOR], 0.83; 95 % confidence interval [CI], 0.20–3.48), nor was pre-treatment CXR stability duration of at least six months (AOR, 0.97; 95 % CI, 0.30–3.10). Similar results were obtained when four-to-six-month stability was considered (AOR, 0.78; 95 % CI, 0.16–3.89). Patients screened overseas (B1 notification) were less likely to develop Class 3 TB (unadjusted OR, 0.15; 95 % CI 0.05–0.44). CONCLUSION: Pre-treatment chest X-ray stability duration was not associated with excluding Class 3 pulmonary TB in this setting, and CXR stability duration cut points may not be as clinically informative as previously understood, but overseas screening is likely an important step in reducing active TB disease burden in the U.S.