Mycobacterium tuberculosis infection in health care workers in rural India: comparison of a whole-blood interferon gamma assay with tuberculin skin testing.
JAMA
; 293(22): 2746-55, 2005 Jun 08.
Article
em En
| MEDLINE
| ID: mdl-15941804
ABSTRACT
CONTEXT Mycobacterium tuberculosis infection in health care workers has not been adequately studied in developing countries using newer diagnostic tests. OBJECTIVES:
To estimate latent tuberculosis infection prevalence in health care workers using the tuberculin skin test (TST) and a whole-blood interferon gamma (IFN-gamma) assay; to determine agreement between the tests; and to compare their correlation with risk factors. DESIGN, SETTING, ANDPARTICIPANTS:
A cross-sectional comparison study of 726 health care workers aged 18 to 61 years (median age, 22 years) with no history of active tuberculosis conducted from January to May 2004, at a rural medical school in India. A total of 493 (68%) of the health care workers had direct contact with patients with tuberculosis and 514 (71%) had BCG vaccine scars.INTERVENTIONS:
Tuberculin skin testing was performed using 1-TU dose of purified protein derivative RT23, and the IFN-gamma assay was performed by measuring IFN-gamma response to early secreted antigenic target 6, culture filtrate protein 10, and a portion of tuberculosis antigen TB7.7. MAIN OUTCOMEMEASURES:
Agreement between TST and the IFN-gamma assay, and comparison of the tests with respect to their association with risk factors.RESULTS:
A large proportion of the health care workers were latently infected; 360 (50%) were positive by either TST or IFN-gamma assay, and 226 (31%) were positive by both tests. The prevalence estimates of TST and IFN-gamma assay positivity were comparable (41%; 95% confidence interval [CI], 38%-45% and 40%; 95% CI, 37%-43%, respectively). Agreement between the tests was high (81.4%; kappa = 0.61; 95% CI, 0.56-0.67). Increasing age and years in the health profession were significant risk factors for both IFN-gamma assay and TST positivity. BCG vaccination had little impact on TST and IFN-gamma assay results.CONCLUSIONS:
Our study showed high latent tuberculosis infection prevalence in Indian health care workers, high agreement between TST and IFN-gamma assay, and similar association between positive test results and risk factors. Although TST and IFN-gamma assay appear comparable in this population, they have different performance and operational characteristics; therefore, the decision to select one test over the other will depend on the population, purpose of testing, and resource availability.
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Base de dados:
MEDLINE
Assunto principal:
Tuberculose
/
Pessoal de Saúde
Tipo de estudo:
Etiology_studies
/
Observational_studies
/
Prevalence_studies
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Prognostic_studies
/
Risk_factors_studies
Limite:
Adult
/
Female
/
Humans
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Male
/
Middle aged
País/Região como assunto:
Asia
Idioma:
En
Ano de publicação:
2005
Tipo de documento:
Article