Serological diagnosis of strongyloidiasis in immunocompetent and immunosuppressed patients based on an electrochemical immunoassay using a flexible device allied to PLS-DA and ROC statistical tools

Abstract

Strongyloidiasis is a tropical disease caused by the nematode called Strongyloides stercoralis. An electrochemical immunosensor was efficiently constructed for the diagnosis of this helminthiasis using the larvae epicuticle as the antigen electrostatically immobilized on the surface of a screen-printed electrode, modified with graphene/ ZnOQDs composite. The mechanism of monitoring was based on the changes in the electrochemical parameters of the device due to the antigen-antibody binding on its interface. The immunosensor was characterized using electrochemical impedance spectroscopy and cyclic voltammetry, evaluating the impedimetric/voltammetric biorecognition of the antigen-antibody complex using the redox group K4Fe(CN)6 as the electrochemical probe. This bioelectronic device detected antibodies in positive serum samples based on the voltammetric profile and electrochemical impedance monitoring. Partial least squares-discriminant analysis showed a coefficient of determination of 0.98, indicating that the model can correctly classify samples as positive or negative for strongyloidiasis, based on the voltammetric profile of samples from immunocompetent patients. The analysis of the root mean square error of cross-validation (0.126), the root mean square error of calibration (0.124), and the root mean square error of prediction (0.100) for the latent variable indicate the optimal precision of the model. Based on the receiver operating characteristic curves, the cutoff was determined for the electrochemical impedance measurements, obtaining a 100% correct classification for immunocompetent patients and just 1.25% false-negatives in cases of immunosuppressed patients. The immunosensor presented excellent specificity in the presence of other helminthiases, including ascaridiasis, diphyllobothriasis, himenolepiasis, cysticercosis, and trichuriasis.