Clinical and radiographic correlates of primary and reactivation tuberculosis: a molecular epidemiology study

Abstract

Context: The traditional teaching that pulmonary tuberculosis characterized by lymphadenopathy, effusions, and lower or mid lung zone infiltrates on chest radiography represents "primary" disease from recently acquired infection, whereas upper lobe infiltrates and cavities represent secondary or reactivation disease acquired in the more distant past, is not based on well-established clinical evidence. Furthermore, it is not known whether the atypical radiograph common in human immunodeficiency virus (HIV)-associated tuberculosis is due to a preponderance of primary progressive disease or altered immunity.

Objective: To analyze the relationship between recently acquired and remotely acquired pulmonary tuberculosis, clinical and demographic variables, and radiographic features by using molecular fingerprinting and conventional epidemiology.

Design, setting, and population: A retrospective, hospital-based series of 456 patients treated at a New York City medical center between 1990 and 1999. Eligible patients had to have had at least 1 positive respiratory culture for Mycobacterium tuberculosis and available radiographic data.

Main outcome measures: Radiographic appearance as measured by the presence or absence of 6 features: upper lobe infiltrate, cavitary lesion, adenopathy, effusions, lower or mid lung zone infiltrate, and miliary pattern. Radiographs were considered typical if they had an upper lobe infiltrate or cavity whether or not other features were present. Atypical radiographs were those that had adenopathy, effusion, or mid lower lung zone infiltrates or had none of the above features.

Results: Human immunodeficiency virus infection was most commonly associated with an atypical radiographic appearance on chest radiograph with an odds ratio of 0.20 (95% confidence interval, 0.13-0.31). Although a clustered fingerprint, representing recently acquired disease, was associated with typical radiograph in univariate analysis (odds ratio, 0.68; 95% confidence interval, 0.47-0.99), the association was lost when adjusted for HIV status.

Conclusions: Time from acquisition of infection to development of clinical disease does not reliably predict the radiographic appearance of tuberculosis. Human immunodeficiency virus status, a probable surrogate for the integrity of the host immune response, is the only independent predictor of radiographic appearance. The altered radiographic appearance of pulmonary tuberculosis in HIV is due to altered immunity rather than recent acquisition of infection and progression to active disease.