Reactivation of Trypanosoma cruzi infection in immunosuppressed patients: contributions for the laboratorial diagnosis standardization.

Diagnosis of parasitemia associated with reactivation of Chagas disease remains a challenge in clinical practice. Since 1990, criteria to establish the differential diagnosis of chronic Chagas disease sporadic parasitemia, and reactivation have been proposed in heart transplant recipients including magnitude of parasitemia, severity of clinical manifestations, evidence of miocarditis, and the finding of Trypanosoma cruzi in tissues1. LUQUETTI & RASSI12 recommended searching for parasites in fresh blood by means of QBC Quantitative Buffy Coat, Strout or micro-hematocrit whenever Chagas disease reactivation is under suspicion, and in negative cases, investigation should continue by means of xenodiagnosis with anticipation of microscopic examination. More recently, SARTORI et al.17 have defined reactivation as the presence of clinical manifestations that are not observed in immunocompetent individuals with chronic T. cruzi infection: detection of parasites by microscopy examination of blood or cerebrospinal fluid (CSF); and high burdens of T. cruzi amastigotes in tissue biopsies or biological samples collected during autopsies. The same authors classified parasitemia in three categories according to microscopic detection: very high parasitemia, high parasitemia and low parasitemia, when T. cruzi was detected by direct examination of blood and/or CSF, when ≥20% of triatomines fed on the patient’s blood were positive, or < 20% of triatomines were positive, respectively (alternatively, in the last case, when only blood culture gave a positive result).