Prevención de la tuberculosis en España en el siglo XXI

Tuberculin skin test in bacille Calmette-Guérin-vaccinated children: how should we interpret the results?

BACKGROUND

The tuberculin skin test (TST) is the most useful method for the diagnosis of tuberculosis (TB). There is no evidence about the effect of bacillus Calmette-Guerin (BCG) vaccine on the interpretation of TST results.

OBJECTIVE

The aim of this study was to evaluate TST results in a population of immigrants and adopted children, analyzing the effect of the vaccine on TST.

METHODS

Cross-sectional observational study including immigrants or adopted children evaluated in our unit between January 2003 and December 2008 was made. Children diagnosed with TB, live attenuated virus vaccinated 2 months earlier, HIV-infected, chronically ill, or under treatment with immunosuppressive agents were excluded. TST was considered the dependent variable. Independent variables were gender, age, geographical origin, BCG scar, nutritional status, immune status, and intestinal parasites infestation.

RESULTS

One thousand seventy-four children were included, 69.6 % are female; their origin includes China (34.7 %), Latin America (20.8 %), India/Nepal (19.4 %), Eastern Europe (15.7 %), and Africa (9.3 %). BCG scar was present in 79 % of children. Mantoux = 0 mm in 84.4 %, <10 mm in 4.1 %, and ≥10 mm in 11.4 %. Only two variables, age and BCG scar, influenced TST result. Risk of a TST false-positive due to BCG disappears 3 years after vaccine administration.

CONCLUSIONS

A history of BCG vaccination at birth does not interfere with TST results in children >3 years old. Under 3 years of age, BCG does interfere with and may cause a false-positive TST result. In these cases, the use of interferon-gamma release assays (IGRAs) is recommended. If IGRAs are not available or when results are indeterminate, ignoring the antecedent of the vaccine is recommended.

La prueba de tuberculina en los controles del niño sano. ¿Debemos cambiar nuestra práctica?

BACKGROUND

The Healthy Child Program and the Preventive Activities and Health Promotion Program involve systematic tuberculin skin testing at distinct ages according to different programs, with variable evaluation of its effectiveness.

OBJECTIVE

To evaluate the tuberculin skin test performed in healthy children within the ongoing basic health program in order to determine whether our activity is effective in detecting latent tuberculin infection.

MATERIAL AND METHODS

A prospective observational study was performed.

POPULATION

Mantoux test performed in children aged 15 months to 14 years during regular health examinations in 22 primary care pediatric clinics over a 12-month period in southern Pontevedra in Spain (catchment population 300,613 inhabitants according to the official census data in January 2003, with 472,444 health cards). Descriptive study and univariate analysis were carried out.

RESULTS

We studied 2,530 children with a mean age of 51.25 months (95 % CI: 49.38-53.13). Eight positive Mantoux tests were registered (0.36 %). There were three positive results in children aged less than 3 years, two positive results in children aged between 4 and 9 years old (all were immigrants) and the remaining positive results were registered in children between 10 and 14 years of age.

CONCLUSIONS

Given that the tuberculin skin test is a good screening test despite its limitations in the control of latent tuberculin infection in children, its indications should be adjusted to ever-changing epidemiological characteristics. According to the results obtained in this study and considering the prevalence of tuberculosis in our environment, we propose that the systematic application of the Mantoux test be discontinued except in children from countries with a high incidence of this disease or risk factors. However, we also recommend that systematic Mantoux testing in adolescence (12-14 years of age) be maintained, when vaccination and various medical examinations are carried out. Epidemiological studies in this age group should simultaneously be performed.