Acta Tropica 150 (2015) 190–195 Contents lists available at ScienceDirect Acta Tropica journal homepage: www.elsevier.com/locate/actatropica Detection of parasite-specific IgG and IgA in paired serum and saliva samples for diagnosis of human strongyloidiasis in northern Paraná state, Brazil Larissa R. Bosqui a , Ana Lúcia R. Gonc ¸ alves b , Maria do Rosário F. Gonc ¸ alves-Pires b , Luiz Antonio Custodio c , Maria Cláudia N.D. de Menezes a , Valter A. Murad c , Fabiana M. de Paula d , Wander R. Pavanelli a , Ivete Conchon-Costa a , Julia Maria Costa-Cruz b , Idessania N. Costa a,∗ a Departamento de Ciências Patológicas, Laboratório de Parasitologia, Universidade Estadual de Londrina, PR, Brazil b Departamento de Imunologia, Microbiologia e Parasitologia, Instituto de Ciências Biomédicas, Universidade Federal de Uberlândia, MG, Brazil c Ambulatório de Especialidades do Hospital Universitário de Londrina, PR, Brazil d Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, SP, Brazil a r t i c l e i n f o Article history: Received 1 April 2015 Received in revised form 28 July 2015 Accepted 29 July 2015 Available online 31 July 2015 Keywords: Strongyloidiasis Immunodiagnostic Saliva Paraná state Brazil a b s t r a c t Human strongyloidiasis is an infection caused by the helminth Strongyloides stercoralis that can be fatal, especially in immunosuppressed patients. The aim of this study is to evaluate parasite-specific IgG and IgA levels using S. venezuelensis third-stage (L3) infective larvae alkaline extract as a heterologous antigen by ELISA in paired serum and saliva samples with improved sensitivity and specificity. Individuals from northern Paraná state, Brazil were divided into three groups: 30 patients copropositive for S. stercoralis (Group I); 30 clinically healthy individuals (Group II); and 30 patients copropositive for other parasites (Group III). The area under ROC curve (AUC), an overall index of diagnostic accuracy, and Kappa index were calculated. Data were analyzed using analysis of variance (ANOVA) followed by a Kruskal–Wallis test. Probability (p) values of <0.05 were regarded as significant. In Group I, IgG was detected in 96.7% serum and in 6.7% saliva samples. IgG was not detected in Group II. In Group III, cross-reactivity was observed for serum IgG in 26.7% and in 6.7% for saliva samples. In Group I, IgA was detected in 76.7% serum and 56.7% saliva samples. In Group II, 3.3% were positive for IgA in serum, whereas IgA was not detected in any saliva samples. Group III showed 6.7% serum and 26.7% saliva-positive samples. The sensitivity values for detection of IgG and IgA in serum samples were 96.7% and 76.7%, respectively. In saliva samples, the sensitivity values for detection of IgG and IgA were 6.7% and 56.7%, respectively. The specificity value was 100% for the detection of IgG in serum and for detection of IgG and IgA in saliva, and 96.7% for detection of IgA in serum samples. The proper choice of immunological diagnosis to supplement parasitological methods is essential to estimate the true prevalence of the parasite, and will permit analysis of population immune response profiles, particularly in northern Paraná state, where there are no previous reports. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Human strongyloidiasis is an infection caused by the intesti- nal worm Strongyloides stercoralis (Bavay, 1876) affecting 30 to 100 million people in 70 countries, predominantly tropical and sub- ∗ Corresponding author at: Departamento de Patologia Experimental – Lab- oratório de Parasitologia Universidade Estadual de Londrina-UEL-Rodovia Celso Garcia Cid Campus Universitário, Cx. Postal 6001, CEP 86051-990 - Londrina – PR, Brazil. E-mail address: idessania@hotmail.com (I.N. Costa). tropical regions (Paula and Costa-Cruz, 2011; Olsen et al., 2009). Epidemiological data from Brazil are derived from isolated stud- ies; however, the average occurrence is around 5.5% (Paula and Costa-Cruz, 2011). In Paraná state, Giraldi et al. (2001) and Buschini et al. (2007) showed positivity rates in children ranging from 0.47 to 2.85%. Studies performed with different age groups in central and Northwest Paraná state reported a positivity rate of 0.9–3.3% (Nascimento and Moitinho, 2005; Toledo et al., 2009; Falavigna et al., 2008). This data demonstrate that Paraná state is an endemic area, according to Pires and Dreyer (1993), who describe three prevalence categories: sporadic (<1%), endemic (1–5%) and hyper- endemic (>5%). http://dx.doi.org/10.1016/j.actatropica.2015.07.026 0001-706X/© 2015 Elsevier B.V. All rights reserved.