Comprovação parasitológica na fase crônica da doença de Chagas por hemoculturas em meio "LIT"

Abstract

Foram realizadas hemoculturas seriadas, semeando-se 0,2 ml de sangue de pacientes com Doença de Chagas na fase crônica, em cada um de 14 tubos de ensaio contendo 6 ml de meio LIT. o exame foi repetido por 3 dias consecutivos, obtendo-se um total de 42 tubos semeados, correspondentes a uma série. A colheita do material foi repetida 30 e 60 dias após. As hemoculturas foram mantidas a 28°C e examinadas com 30, 45 e 60 dias. Dos 1337 tubos semeados 54 apresentaram-se positivos, observando-se que a maior freqüência de tubos positivos ocorreu após 45 dias de incubação, o que permitiu o diagnóstico parasitológico de 13 entre 15 pacientes examinados (86,6%). A hemocultura seriada em. meio LIT deve ser considerada como uma técnica a ser utilizada na triagem de pacientes para ensaios clínicos ou outros tipos de pesquisas que indiquem a necessidade de prévio diagnóstico parasitológico. Por ser um método trabalhoso e demorado não é possível recomendar o seu emprego em diagnóstico de rotina.

Detection and characterization of antigens in urine of patients with acute, congenital, and chronic Chagas' disease

“…Although this reactivity of 32.6% in studied samples is much lower than that achieved in specimens from recently infected children, the well-known limitations of parasitological diagnosis during the chronic stage of T. cruzi infection must be taken into account. Xenodiagnosis and hemoculture may confirm only 20 to 50% of chronic cases, which usually present reduced parasitemia levels (20), and have two drawbacks: the need of special facilities and the lengthy period (60 to 90 days) required to obtain reliable results. As observed for parasite detection by xenodiagnosis, the sensitivity of the ELISA for demonstration of antigenuria in the chronic phase of Chagas' disease may be improved by increasing the number of determinations per patient.…”

“…Parasitological methods used for diagnosis of recently acquired T. cruzi infections, although highly sensitive, are inadequate for large-scale assays. In addition, these procedures confirm only 20 to 50% of infections when performed for chronic chagasic patients (20). Detection of circulating antigens has opened a new approach to the demonstration of T. cruzi in infected individuals (3,9,11,15,25).…”

Changes in the hemoculture methodology improve the test positivity

“…The accumulated positivity rate considering the first and second series gave a 37/38 (97.4%) of positive patients. Mourão and Chiari (1975), using LIT and the protocol of Albuquerque et al (1972) observed a positivity of 86.6% (n=13). In Argentina Jorg and Baez (1993), obtained a positivity rate of 86.6% in asymptomatic patients with chronic Chagas disease by repeating hemocultures until eight times using LIT.…”