Tuberculin reactivity and the risk of tuberculosis: a review

SETTING: Although various studies have examined the association between tuberculin reactivity and the risk of tuberculosis (TB), this evidence has not been collated and examined to determine the strength and consistency of the association across multiple studies.

OBJECTIVE: To review the evidence supporting the association between tuberculin reactivity and the risk of TB.

DESIGN: Prospective studies which included raw data on the incidence of TB according to three or more tuberculin reactor categories were located using electronic search methods. The findings of these studies were recalibrated if necessary and compared.

RESULTS: All 11 studies identified demonstrated that increased tuberculin skin test (TST) reactivity was associated with an increased risk of TB, and several found that low tuberculin reactivity was associated with a protective effect. The magnitude of the association between TST reactivity and the risk of TB varied substantially. The association between tuberculin reactivity and the risk of TB was greater among studies that reported a lower incidence of TB among the smallest tuberculin reactor category.

CONCLUSION: All studies reviewed support a positive association between tuberculin reactivity and the risk of TB. However, this review found a substantial degree of variation in the extent of increased risk associated with larger tuberculin reactions.