Advanced pulmonary tuberculosis in Alameda County: Ten-year incidence and risk factors

Abstract

Background: Advanced pulmonary tuberculosis (APT) may reflect delays in tuberculosis (TB) diagnosis and contribute to ongoing disease transmission and poor outcomes. We characterized trends and factors associated with APT over ten years in a high TB-burden county within the United States.

Methods: We evaluated microbiologically and clinically confirmed TB cases reported to the Alameda County Public Health Department during 2010-2019. APT was defined as the presence of cavitation on chest imaging and positive acid-fast bacilli sputum smear. Over the ten-year period, we determined overall incidence and annual trends, and conducted multivariable logistic regression to identify sociodemographic and clinical factors associated with APT.

Results: We included 997 cases with pulmonary TB, of which 128 (12.8 %) had APT. The 10-year incidence of APT was 8.8 cases per 100,000, with no significant change in proportion over time. The median age of cases with APT were 50 years (IQR 32-61), 68 % were male, and 78.9 % were non-US-born. On multivariable assessment, APT cases were more likely than non-APT cases to use drugs in the past year (aOR 2.43, 95 % CI 1.10-35.09), to have diabetes (aOR 2.51, 95 % CI: 1.59-3.96), and be HIV negative (aOR 9.32 versus HIV positive, 95 % CI 1.87-169.77). While US nativity was not significantly associated with APT, it was an effect modifier. In stratified analysis, APT was more likely among those with drug-use in the last year among US-born, while diabetes was associated with APT among non-US-born individuals.

Conclusions: APT remains a substantial proportion of TB cases. Efforts to increase awareness and access to care are needed for key risk groups including those with recent drug use or diabetes, with consideration of cultural and linguistic factors given differences by US nativity.

Keywords: Delayed diagnosis; Epidemiology; Surveillance; Tuberculosis; United States.

Fig. 1

Flowchart of pulmonary tuberculosis case classification, Alameda County, 2010–2019. Abbreviations: AFB: acid-fast bacilli; APT, Advanced pulmonary tuberculosis; RVCT, Report of a Verified Case of Tuberculosis; ^aNon-respiratory AFB smear taken, n = 8; AFB smear not done, n = 6. ^bCharacteristics of APT defined as the presence of cavitation on chest radiograph, and a positive acid-fast bacilli sputum smear result. One characteristic of APT was defined as having either cavitation on chest radiograph or a positive acid-fast bacilli sputum smear result. For the purpose of these analyses, non-APT (n=869) included those with no features of APT (n=499) and one feature of APT (n=370).

Fig. 2

Trends^a in proportion of pulmonary tuberculosis cases with advanced pulmonary tuberculosis, by year and nativity, Alameda County, 2010–2019. Abbreviation: APT, Advanced pulmonary tuberculosis. ^aAll trends, p > 0.05.