Evaluation of polymerase chain reaction in the diagnosis of pulmonary tuberculosis in indigenous and non-indigenous patients.
OBJECTIVE
To evaluate the accuracy of bacteriological methods and of polymerase chain reaction (with primers specific for IS6110 of the Mycobacterium tuberculosis complex) in testing sputum samples from indigenous (Amerindian) and non-indigenous patients.


METHODS
A total of 214 sputum samples (154 from indigenous patients and 60 from non-indigenous patients) were analyzed in order to determine the accuracy of smear microscopy (direct and concentrated versions) for acid-fast bacilli, culture, and polymerase chain reaction.


RESULTS
Both microscopy methods presented low sensitivity in comparison with culture and polymerase chain reaction. Specificity ranged from 91% to 100%, the concentrated acid-fast smear technique being the least specific. Nontuberculous mycobacteria were isolated three times more frequently in samples from indigenous patients than in those from non-indigenous patients. False-positive and false-negative polymerase chain reaction results were more common in the indigenous population.


CONCLUSIONS
Positivity and isolation of nontuberculous mycobacteria in the acid-fast smear in conjunction with polymerase chain reaction positivity raise the following hypotheses: nontuberculous mycobacteria species with DNA regions homologous to, or even still possessing, the M. tuberculosis IS6110 exist in the Amazon; colonization of the oropharynx or of a tuberculous lesion accelerates the growth of the nontuberculous mycobacteria present in the sputum samples, making it impossible to isolate M. tuberculosis; A history of tuberculosis results in positivity for M. tuberculosis DNA. The absence of bacteriological positivity in the presence of polymerase chain reaction positivity raises questions regarding the inherent technical characteristics of the bacteriological methods or regarding patient history of tuberculosis.
Santos
Rose Mary Corrêa
RM
Hospital Universitário Getúlio Vargas, Manaus, Amazonas, Brazil.
Ogusku
Mauricio Morishi
MM
Miranda
José de Moraes
Jde M
Dos-Santos
Maria Cristina
MC
Salem
Julia Ignez
JI
D001431:Bacteriological Techniques; D004269:DNA, Bacterial / Q000032:analysis; D006801:Humans; D007199:Indians, South American; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000302:isolation & purification*; D016133:Polymerase Chain Reaction / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013183:Sputum / Q000382:microbiology*; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis*
D004269:DNA, Bacterial