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Memórias do Instituto Oswaldo Cruz
Fundação Oswaldo Cruz, Fiocruz
ISSN: 1678-8060 EISSN: 1678-8060
Vol. 91, Num. 2, 1996, pp. 191
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Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 91(1), Mar/Apr 1996
RESEARCH NOTE: Evaluation of Enzyme-Linked Immunosorbent Assay
for the Serodiagnosis of Tuberculosis in Patients with AIDS in Cuba
Ernesto Montoro, Raul Diaz, Miguel Echemendia, Jose A Valdivia
Instituto de Medicina Tropical 'Pedro Kouri' (IPK), Laboratorio
Nacional de Referencia de Mycobacteria y Tuberculosis, Apdo 601,
Marianao 13, Ciudad de La Habana, Cuba
Code Number: OC96037
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Key words: ELISA - tuberculosis - AIDS - PPD - Cuba
Tuberculosis is a major complication of AIDS, and the diagnosis
of tuberculosis in patients with AIDS is difficult because the
presentation of the former disease is often not typical and
because the yield of standard microbiological techniques may
be low (TM Daniel et al. 1994 Tubercle Lung Dis
75: 33-37).
Recently, we used an Enzyme-Linked Immunosorbent Assay (ELISA)
for detection of IgG antibodies to purified protein derivative
(PPD) antigen of Mycobacterium tuberculosis for the
diagnosis of pulmonary tuberculosis. The specificity and the
sensitivity were 95.33% and 82% respectively. We used a cut off
point of 0,320 (E Montoro et al. 1994 Rev Cub Med Trop
46: 90-93).
In this paper we applied the ELISA from sera (25) of patients
of tuberculosis with AIDS in Cuba during an outbreak from July
1993 to March 1994. Sera (25) from patients with
tuberculosis without AIDS were also included. In all cases,
diagnosis was bacteriologically confirmed at the same time.
Positive results in the ELISA test were obtained in 5 out of
25 sera (20%) from patients with AIDS-tuberculosis, however
in 21 sera (84%) from patients with tuberculosis without
AIDS were positive. As it is noted the sensitivity of the test
in AIDS-tuberculosis patients was much lower than in our
previously described study (Montoro et al. loc. cit.).
Our results agree with other reports using ELISA for detection
of PPD as antigen and showing severely diminished sensitivity
in AIDS patients (IN Kantor et al. 1990 Am Rev Respir Dis
141: A264, L Barrera et al. 1992 Tubercle Lung Dis
73: 187-191). This could be explained by the profound
changes in cell immunity and the impairment of humoral immunity
in AIDS patients (JFC Figueiredo, AA Machado 1992 Braz J Med
Biol Res 25: 611-618).
In Uganda, a country with high rates of AIDS and tuberculosis
infections, Daniel et al. (loc. cit.) studied an ELISA for
IgG antibody to a 30,000 dalton antigen of M.
tuberculosis. Test sensitivity dropped from 62% in non
HIV infected tuberculosis patients to 28% in HIV infected
patients. However, although the prevalence of both infections,
is low in Cuba, and in spite of the small number of sera
studied here our results coincide with Daniel regarding this
technique in AIDS patients with tuberculosis.
In summary, our findings show that the sensitivity of
ELISA technique may decrease when applying it in AIDS
patients, independent of the rate of prevalence of both
diseases.
This work received financial support from SAREC (Sweden).
Received 3 March 1995
Accepted 9 November 1995
Copyright 1996 Fundacao Oswaldo Cruz
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