Clinical microbiology and infection : the official publication of the European Society of Clinical Microbiology and Infectious Diseases 2016 6 15() pii 10.1016/j.cmi.2016.06.001
According to the World Health Organization (WHO), chronic Chagas disease (CD) diagnosis is based on two serological techniques. To establish a definitive diagnosis, the results must be concordant. In cases of discordances, the WHO proposes repeating serology in a new sample, and if results remain inconclusive, a confirmatory test should be performed. This study, conducted at two Tropical Medicine Units in Europe during four years, aims to assess the diagnostic yield of TESA-blot as a confirmatory technique in patients with inconclusive and discordant results. Out of 4939 individuals screened, 1124 (22.7%) obtained positive and 165 (3.3%) discordant results. Serology was repeated in 88/165 sera and discrepancies were solved in 25/88 (28.4%) cases. Patients without a definitive diagnosis were classified in two different groups: Group 1, including patients with inconclusive results despite retesting (n=63), and Group 2, including patients with discordant results not retested (n=77). TESA-blot was performed for all of Group 1 and 39/77 of Group 2 and was positive for 33/63 (52.4%) and 21/39 (53.8%), respectively. Analysis of Group 1 results showed a moderate agreement between results of the ELISA based on native antigen and TESA-blot (kappa=0.53). In contrast, a clear disagreement was observed between the ELISA based on recombinant antigens and TESA-blot (kappa<0). There are a sizeable proportion of patients suspected to have CD with inconclusive results or in whom re-testing is not feasible. TESA-blot was positive in half of these patients, highlighting the need of a confirmatory assay in European centres taking care of exposed individuals.