Dealing with initial inconclusive serological results for chronic Chagas disease in clinical practice.

Most guidelines for Chagas disease recommend the performance of two serological tests in order to detect it. However, inconclusive results may arise from this strategy. The aim was to describe whether serological follow-up together with the patient's clinical characteristics could clarify the outcome of patients with initial inconclusive test results. In this retrospective case series, all results of Chagas disease serological tests and outpatient visits recorded from 2004 to 2008 were screened for inclusion. The inclusion criterion was clinical suspicion of chronic Chagas disease and the exclusion criteria were previous diagnosis of Chagas disease, suspicion of acute Chagas disease, and serological tests with no corresponding medical evaluation. A total of 1,732 patients were analyzed. Chronic Chagas disease prevalence was 21.1%. After the initial set of serological tests, 2.9% of patients had inconclusive test results. Most of these patients had definite diagnosis after clinical follow-up and the repetition of serological tests in a new blood sample. Loss to follow-up while partaking in the diagnostic investigation reached 17.7%. The prevalence of initial inconclusive serological tests for chronic Chagas disease is low. Clinical evaluations and follow-up clarify the definite diagnosis. Noncompliance to follow-up is a frequent problem. Strategies to reduce inconclusive results and noncompliance are discussed.