Radiographic predictors of subsequent reactivation of tuberculosis

A cohort of migrants to Australia (n = 7265) selected to be at increased risk of tuberculosis (TB) were assessed at the Liverpool Chest Clinic, Sydney, between 1984 and 2003.

To assess the reproducibility and predictive value of various radiographic criteria for predicting the subsequent development of TB.

A nested case control study was conducted. Cases were those who had a confirmed diagnosis of TB during follow-up (n = 60). A random sample of 107 controls was selected. Initial chest X-rays were read independently and blinded to case vs. control status by two readers according to two classification systems. Agreement was quantified as weighted kappa (kappaw). Sensitivity and specificity for subsequent TB were estimated.

There was moderate agreement between readers for both classification systems (kappaw 0.67 and 0.60, respectively). The presence of calcified nodular densities or fibrosis together with non-calcified nodular densities in mid and/or upper lung zones or the presence of a pulmonary infiltrate typical of TB had a sensitivity of 66% for subsequent pulmonary TB and a specificity of 82%. Minor abnormalities or findings consistent with past primary TB infection alone were not predictive of subsequent TB.

Radiographic screening can be helpful in identifying individuals at increased risk of subsequent TB.