Abstract
BackgroundDespite the improvements in diagnostic tools for detection of Trypanosoma cruzi in human blood samples, the isolation of parasite from bloodstream in the chronic phase of Chagas disease is challenging. Thus, there is an increasing interest in the development of strategies that allow an accurate monitoring of the parasite load in bloodstream of Chagas disease patients. Given that, the comparison of a classical diagnostic method such as blood culture and multiplex quantitative real-time PCR (qPCR) was few explored so far. Therefore, this study aimed to compare the detection and quantification of T. cruzi load in the circulating blood of patients with chronic Chagas disease, using blood culture and qPCR techniques.Methods⁄Principal findingsThe multiplex real-time quantitative PCR assay (qPCR) based on TaqMan technology was evaluated in 135 blood samples from 91 patients with chronic Chagas disease presenting indeterminate (asymptomatic, n = 23) and cardiac (chronic cardiomyopathy, n = 68) forms, in comparison with the classical blood culture (BC) technique. The total positivity of qPCR and BC was 58.5% and 49.6%, respectively. The median parasite load of all positive patients was 1.18 [0.39–4.23] par. eq.⁄mL, ranging from 0.01 to 116.10 par. eq.⁄mL. We did not find significant differences between T. cruzi load with age and distinct clinical manifestations of patients.Conclusions/SignificanceOur data suggest that qPCR can be an auxiliary tool for studies that require T. cruzi isolation from the bloodstream of patients with chronic Chagas disease, after the establishment of a parasite load cut-off that guarantees a relative success rate of parasite isolation using BC technique.
Highlights
The diagnosis of Trypanosoma cruzi infection should be carried out using different methodologies, depending on the stage of the disease
Patients were subjected to a standard screening protocol that included medical history, physical examination, ECG, laboratory and chest X-ray examinations, disease evolution by echocardiography and characterization according to the clinical classification of chronic Chagas disease [35]
Data concerning blood collection date, age, T. cruzi discrete typing units (DTUs), blood culture (BC) positivity, parasite load, clinical form of disease for each patient are given in Tables 1 and 2
Summary
The diagnosis of Trypanosoma cruzi infection should be carried out using different methodologies, depending on the stage of the disease. Indirect parasitological diagnostic methods such as xenodiagnosis and blood culture (BC) depend on the presence of at least one intact trypomastigote form for its growth in culture medium. The results of these methods can take up to 120 days and still be doubtful [6, 11,12,13]. Despite the improvements in diagnostic tools for detection of Trypanosoma cruzi in human blood samples, the isolation of parasite from bloodstream in the chronic phase of Chagas disease is challenging. This study aimed to compare the detection and quantification of T. cruzi load in the circulating blood of patients with chronic Chagas disease, using blood culture and qPCR techniques
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