[Factors associated with latent tuberculosis infection in the contacts of tuberculosis patients].
BACKGROUND
As tuberculosis control programs have reached acceptable levels in the identification and treatment of persons with active tuberculosis, the next step should be to develop methods of preventing new cases. Persons with latent tuberculosis infection (LTI) are considered to have a higher risk of developing active tuberculosis. The objective of this study was to evaluate the prevalence of LTI and its associated factors in the contacts of tuberculosis patients.


METHODS
We studied the contacts of tuberculosis patients who were examined in the Center for Tuberculosis Control and Prevention in Lleida (Spain) from 1991-1997. Factors associated with the index case (demographic, radiographic, bacteriologic and therapeutic) and tuberculin skin test results and demographic data in contacts were collected. Data on HIV infection, injection drug use and alcohol consumption in tuberculosis patients were also collected. The associations were assessed by obtaining crude and adjusted odds ratios.


RESULTS
The prevalence of LTI among contacts was 36.1% (780/2,161). In the multivariate analysis a higher frequency of LTI was detected in contacts older than 14 years (ORa = 3.34; 95% CI, 2.51-4.45), contacts who had a higher degree of exposure to the index case (ORa = 1.96; 95% CI, 1.59-2.42), contacts of pulmonary tuberculosis patients (ORa = 1.54; 95% CI, 1.01-2.35), contacts of patients with a positive sputum smear (ORa = 1.51; 95% CI, 1.15-1.99), contacts of patients with caverns on chest x-ray (ORa = 1.27; 95% CI, 1.01-1.61) and contacts of patients with delayed treatment (ORa = 1.31; 95% CI, 1.05-1.62).


CONCLUSIONS
The overall prevalence of LTI in the contacts of patients with tuberculosis was high. Among the factors studied, delayed treatment in the index case was independently associated with the frequency of LTI in tuberculosis contacts. Measures for the early diagnosis and treatment of tuberculosis should be intensified.
Alsedà
Miquel
M
Sección de Epidemiología, Delegación Territorial del Departamento de Sanidad y Seguridad Social de Lleida, Facultad de Medicina, Universidad de Lleida, Spain. miquel.alseda@cirurgia.udl.es
Godoy
Pere
P
D000293:Adolescent; D000328:Adult; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D013030:Spain / Q000453:epidemiology; D014376:Tuberculosis / Q000453:epidemiology* / Q000635:transmission