Use of a Latent Class Analysis in the Diagnosis of Chronic Chagas Disease in the Washington Metropolitan Area

Abstract

Abstract Background The diversity of individuals at risk for Trypanosoma cruzi infection in the United States poses challenges for diagnosis. We evaluated the diagnostic accuracy of Food and Drug Administration (FDA)-cleared tests in the Washington Metropolitan area (WMA). Methods In total, 1514 individuals were evaluated (1078 from Mexico, Central and northern South America [TcI-predominant areas], and 436 from southern South America [TcII/V/VI-predominant areas]). Optical density (OD) values from the Hemagen EIA and Chagatest v.3 Wiener, and categorical results of the IgG-TESA-blot (Western blot with trypomastigote excretory-secretory antigen), and the Chagas detect plus (CDP), as well as information of area of origin were used to determine T. cruzi serostatus using latent class analysis. Results We detected 2 latent class (LC) of seropositives with low (LC1) and high (LC2) antibody levels. A significantly lower number of seropositives were detected by the Wiener, IgG-TESA-blot, and CDP in LC1 (60.6%, P < .001, 93.1%, P = .014, and 84.9%, P = .002, respectively) as compared to LC2 (100%, 100%, and 98.2%, respectively). LC1 was the main type of seropositives in TcI-predominant areas, representing 65.0% of all seropositives as opposed to 22.8% in TcII/V/VI-predominant areas. The highest sensitivity was observed for the Hemagen (100%, 95% confidence interval [CI]: 96.2–100.0), but this test has a low specificity (90.4%, 95% CI: 88.7–91.9). The best balance between positive (90.9%, 95% CI: 83.5–95.1), and negative (99.9%, 95% CI: 99.4–99.9) predictive values was obtained with the Wiener. Conclusions Deficiencies in current FDA-cleared assays were observed. Low antibody levels are the main type of seropositives in individuals from TcI-predominant areas, the most frequent immigrant group in the United States.