Abstract
A Trypanosoma cruzi Loopamp kit was recently developed as a ready-to-use diagnostic method requiring minimal laboratory facilities. We evaluated its diagnostic accuracy for detection of acute Chagas disease (CD) in different epidemiological and clinical scenarios. In this retrospective study, a convenience series of clinical samples (venous blood treated with EDTA or different stabilizer agents, heel-prick blood in filter paper or cerebrospinal fluid samples (CSF)) from 30 infants born to seropositive mothers (13 with congenital CD and 17 noninfected), four recipients of organs from CD donors, six orally–infected cases after consumption of contaminated guava juice and six CD patients coinfected with HIV at risk of CD reactivation (N = 46 patients, 46 blood samples and 1 CSF sample) were tested by T. cruzi Loopamp kit (Tc LAMP) and standardized quantitative real-time PCR (qPCR). T. cruzi Loopamp accuracy was estimated using the case definition in the different groups as a reference. Cohen’s kappa coefficient (κ) was applied to measure the agreement between Tc LAMP (index test) and qPCR (reference test). Sensitivity and specificity of T. cruzi Loopamp kit in blood samples from the pooled clinical groups was 93% (95% CI: 77–99) and 100% (95% CI: 80–100) respectively. The agreement between Tc LAMP and qPCR was almost perfect (κ = 0.92, 95% CI: 0.62–1.00). The T. cruzi Loopamp kit was sensitive and specific for detection of T. cruzi infection. It was carried out from DNA extracted from peripheral blood samples (via frozen EDTA blood, guanidine hydrochloride-EDTA blood, DNAgard blood and dried blood spots), as well as in CSF specimens infected with TcI or TcII/V/VI parasite populations. The T. cruzi Loopamp kit appears potentially useful for rapid detection of T. cruzi infection in congenital, acute and CD reactivation due to HIV infection.
Highlights
Chagas disease (CD), known as American trypanosomiasis, is a neglected tropical disease caused by the protozoan parasite Trypanosoma cruzi that affects about 6 to 7 million people worldwide, mainly in endemic areas of 21 Latin American countries [1].Transmission of T. cruzi occurs by the vectorial route, including oral transmission by consuming food or beverages contaminated with triatomine faeces, by congenital transmission, blood transfusion or solid organ transplantation from infected donors, and by laboratory accidents.The disease evolves from an acute phase when the infection is acquired, which is frequently asymptomatic, to a chronic phase that may develop, in up to 30% of cases, cardiac disease, and in 10% of cases digestive mega-syndromes, neurological and/or mixed complications [2,3]
The aim of this study was to evaluate a kit prototype (T. cruzi Loopamp or T. cruzi Loopamp kit (Tc LAMP)) based on loop-mediated isothermal amplification (LAMP) for molecular diagnosis of acute Chagas disease in well-characterized individuals, collected in real life conditions, such as newborns or infants born to Chagas disease mothers aiming to detect congenital Chagas disease, recipients of organs from Chagas disease donors who acquired T. cruzi infection after transplantation, persons with oral Chagas disease acquired after consumption of a contaminated meal, and HIV/T. cruzi coinfected patients at risk of Chagas disease reactivation due to immunosuppression
The present study aimed to evaluate the performance of T. cruzi Loopamp in panels of clinical samples from acute CD patients belonging to clinical settings of high vulnerability, in which an accurate and easy to handle infection detection method could significantly improve patient diagnosis [10,11]
Summary
The disease evolves from an acute phase when the infection is acquired, which is frequently asymptomatic, to a chronic phase that may develop, in up to 30% of cases, cardiac disease, and in 10% of cases digestive mega-syndromes, neurological and/or mixed complications [2,3]. A proportion of chronically yet asymptomatic infected people, facing an immunocompromised condition due to HIV infection, organ transplantation, autoimmune disease, or oncologic treatments, may experience CD reactivation, evolving to severe clinical forms of the disease with high parasitemia [4]. Serological assays for T. cruzi infection are not always applicable; for serodiagnosis of infants born to seropositive mothers it is necessary to wait until at least nine months of age [9], and in severely immunocompromised CD patients, false seronegative results may be obtained [4]
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