ABSTRACT
The performance of distinct serological tests (rK39-ICT, IFAT, DAT-LPC, FC-Simplex IgG1) was assessed and a laboratorial algorithm was proposed for accurate diagnosis of VL. DAT-LPC and FC-Simplex IgG1 showed outstanding accuracy (AUC = 0.93) to identify VL patients. The use of a sequential serological algorithm (rK39-ICT screening followed by DAT-LPC or FC-Simplex IgG1) improved the global accuracy for VL (97.2%) diagnosis. An alternative approach for diagnosis of VL has been also assessed for interchangeable use of serum/whole blood lysate samples in DAT-LPC and FC-Simplex IgG1. Our data showed an outstanding agreement for the results obtained with whole blood lysate samples as compared to serum samples (DAT-LPC =100%; FC-Simplex IgG1 = 99%). Together, these findings provide insights to improve the current overall accuracy of VL diagnosis and present innovative laboratorial tests and alternative samples from use in public health services.
Subject(s)
Algorithms , Antibodies, Protozoan/blood , Antigens, Protozoan/immunology , Immunoglobulin G/blood , Leishmania donovani/immunology , Leishmaniasis, Visceral/diagnosis , Reagent Kits, Diagnostic , Serologic Tests , Adolescent , Adult , Aged , Biomarkers/blood , Brazil , Case-Control Studies , Child , Child, Preschool , Female , Flow Cytometry , Host-Parasite Interactions , Humans , Infant , Leishmaniasis, Visceral/blood , Leishmaniasis, Visceral/immunology , Leishmaniasis, Visceral/parasitology , Male , Middle Aged , Predictive Value of Tests , Reproducibility of Results , Young AdultABSTRACT
The aim of this study was to evaluate the performance of conventional serology (Q-Preven™ and ELFAVIDAS™) and flow cytometry-based serologic tools for early serologic diagnosis of congenital toxoplasmosis. The study groups included prospectively confirmed cases of congenital toxoplasmosis (TOXO=88) and age-matching non-infected controls (NI=15).The results demonstrated that all samples tested positive/indeterminate for anti-T. gondii IgM screening at birth using air-dried whole blood samples. Serum samples collected at 30-45days after birth tested positive for ELFAVIDAS™ IgG in both groups. While all NI tested negative for ELFAVIDAS™ IgM and IgA, only 78% and 36% of TOXO tested positive for IgM and IgA, respectively. Flow cytometry-based anti-T. gondii IgM, IgA and IgG reactivity displayed moderate performance with low sensitivity (47.6%, 72.6% and 75.0%, respectively). Regardless the remarkable specificity of IgG1, IgG2 and IgG3 subclasses for early diagnosis, weak or moderate specificity was observed (Se=73.9%, 60.2% and 83.0%, respectively). The analysis of IgG avidity indices (AI) demonstrated the highest performance among the flow cytometry-based methods (Se=96.6%; Sp=93.3%), underscoring the low avidity index (AI<60%) within TOXO (97.0%) in contrast with the high avidity index (AI>60%) in NI (93%). Analysis of anti-T. gondii IgG and IgG3 reactivity for mother:infant paired samples may represent a relevant complementary tests for early diagnosis. In conclusion, a feasible high-standard algorithm (Accuracy=97.1%) was proposed consisting of Q-Preven™ IgM screening at birth, followed by ELFAVIDAS™ IgM and flow cytometric IgG avidity analysis at 30-45days after birth as a high performance tool for early serological diagnosis of congenital toxoplasmosis.
