Trypanosoma cruziloop-mediated isothermal amplification (Trypanosoma cruziLoopamp) kit for detection of congenital, acute and Chagas disease reactivation

ATrypanosoma cruziLoopamp 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 byT.cruziLoopamp kit (TcLAMP) and standardized quantitative real-time PCR (qPCR).T.cruziLoopamp accuracy was estimated using the case definition in the different groups as a reference. Cohen's kappa coefficient (kappa) was applied to measure the agreement betweenTcLAMP (index test) and qPCR (reference test). Sensitivity and specificity ofT.cruziLoopamp kit in blood samples from the pooled clinical groups was 93% (95% CI: 77-99) and 100% (95% CI: 80-100) respectively. The agreement betweenTcLAMP and qPCR was almost perfect (kappa = 0.92, 95% CI: 0.62-1.00). TheT.cruziLoopamp kit was sensitive and specific for detection ofT.cruziinfection. 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. TheT.cruziLoopamp kit appears potentially useful for rapid detection ofT.cruziinfection in congenital, acute and CD reactivation due to HIV infection. Author summary The aim of this study was to evaluate a kit prototype (T.cruziLoopamp orTcLAMP) 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 acquiredT.cruziinfection after transplantation, persons with oral Chagas disease acquired after consumption of a contaminated meal, and HIV/T.cruzicoinfected patients at risk of Chagas disease reactivation due to immunosuppression. Different types of clinical samples were tested; peripheral blood samples treated with ethylenediamine tetraacetic acid (EDTA) as anticoagulant or with guanidine hydrochloride or DNAgard stabilizer agents, as well as dried blood spots and cerebrospinal fluid samples. The performance ofTcLAMP was estimated using the case definition in the different groups as a reference and all test kit results were compared to those obtained using standardized duplex real-time PCR (qPCR) in the same clinical samples. Sensitivity and specificity ofTcLAMP in blood samples from the pooled clinical groups were 93% (95% CI: 77-99) and 100% (95% CI: 80-100) respectively. The agreement betweenTcLAMP and qPCR was almost perfect (kappa index of Cohen = 0.92, 95% CI: 0.62-1.00).TcLAMP was sensitive and specific for detection ofT.cruziinfection in the tested samples, encouraging prospective field studies to validate its use for rapid detection ofT.cruziinfection in congenital, acute and CD reactivation due to HIV infection.