[Tuberculin reaction size in tuberculosis patient contacts]

The purpose of this study was to explore the association between tuberculin reaction size in contacts with positive tuberculin skin test results and a variety of contact and index patient variables.

We reviewed the contact investigation records for tuberculosis patients identified by the Tuberculosis Prevention and Control Center of Lleida, Spain, over a period of 7 years. Patients with pulmonary and/or extrapulmonary disease were included. Tuberculosis infection had been diagnosed using the Mantoux skin test with 2 tuberculin units of purified protein derivative RT-23, and tuberculosis disease had been detected on the basis of clinical data, chest radiographs, and cultures. We examined the association between tuberculin reaction size and contact age, close contact with index patients with positive sputum smears, and diagnosis of tuberculosis disease in contacts. Associations were analyzed using the chi(2) test for linear trend.

Tuberculin reaction size was 10 mm or greater in 85.9% of the 768 contacts analyzed and 15 mm or greater in 63.8%. The percentage of contacts under 15 years of age (P=.006) who had close contact with an index patient with a positive sputum smear (P=.013) and who were diagnosed with tuberculosis disease (P=.029) increased with tuberculin reaction size.

We found that larger tuberculin reaction size in contacts with positive tuberculin skin test results was most frequently associated with recent infections in the contact, close contact with an index patient with a positive sputum smear, and diagnosis of tuberculosis disease in the contact.