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Clinical and Diagnostic Laboratory Immunology, January 2004, p. 94-97, Vol. 11, No. 1
1071-412X/04/$08.00+0     DOI: 10.1128/CDLI.11.1.94-97.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Immunoglobulin A (IgA) and IgG Immune Responses against P-90 Antigen for Diagnosis of Pulmonary Tuberculosis and Screening for Mycobacterium tuberculosis Infection

Marcus B. Conde,1* Philip Suffys,2 Jose Roberto Lapa e Silva,1 Afranio L. Kritski,1 and Susan E. Dorman3

Unidade de Pesquisa em Tuberculose, Instituto de Doenças do Tórax, Hospital Universitário Clementino Fraga Filho, Universidade Federal do Rio de Janeiro,1 Laboratório de Biologia Molecular e Diagnóstico de Doenças Infecciosas e Laboratório de Hanseníase Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro, Brazil,2 Center for Tuberculosis Research, Johns Hopkins University School of Medicine, Baltimore, Maryland3

Received 28 August 2003/ Accepted 29 October 2003

The purpose of the present study was to evaluate the usefulness of detection of serum immunoglobulin A (IgA) and IgG antibodies directed against the mycobacterial P-90 antigen for the diagnosis of active pulmonary tuberculosis (PTB) among symptomatic individuals and for the detection of Mycobacterium tuberculosis infections among close contacts of PTB patients. Two commercially available enzyme immunoassay (EIA) kits (IgA EIA-TB [EIA-IgA] and IgG EIA-TB [EIA-IgG]; Kreatech Diagnostics) were evaluated in a blinded fashion by using stored serum samples from 268 individuals, including 69 patients with PTB, 41 patients with diseases other than tuberculosis (TB), 12 subjects with healed PTB, 39 close contacts of PTB patients, and 107 healthy volunteers. For the EIA-IgA, the sensitivity was 74% and the specificity was 68% when a cutoff determined by a receiver operator characteristic curve was used. For the EIA-IgG, the sensitivity was 69% and the specificity was 64%. The EIA-IgA was positive for 54% of healthy close contacts of PTB patients but only 8% of healthy controls without contact with a PTB patient or a prior personal history of TB (P < 0.001). The relatively low sensitivities and specificities of these serologic tests make them poor tools for the diagnosis of PTB among patients with suspected PTB. However, the relatively high prevalence of positive EIA-IgA results among healthy close contacts of PTB patients warrants further evaluation of this test with close contacts and other populations at risk for recent M. tuberculosis exposure and development of disease.

* Corresponding author. Mailing address: Hospital Universitário Clementino Fraga Filho, Universidade Federal do Rio de Janeiro, Av. Brigadeiro Trompowsky, s/n° 4° andar, Unidade de Pesquisa em Tuberculose, Ilha do Fundão, Rio de Janeiro, RJ CEP 21941-590, Brazil. Phone: 55-21-2562-2426. Fax: 55-21-2562-2853. E-mail: marcusconde{at}hucff.ufrj.br.

Clinical and Diagnostic Laboratory Immunology, January 2004, p. 94-97, Vol. 11, No. 1
1071-412X/04/$08.00+0     DOI: 10.1128/CDLI.11.1.94-97.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.





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