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Chagas Disease Serological Test Performance in U.S. Blood Donor Specimens

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Chagas Disease Serological Test Performance in U.S. Blood Donor Specimens

Jeffrey D Whitman et al. J Clin Microbiol.

Abstract

Chagas disease affects an estimated 300,000 individuals in the United States. Diagnosis in the chronic phase requires positive results from two different IgG serological tests. Three enzyme-linked immunosorbent assays (ELISAs) (Hemagen, Ortho, and Wiener) and one rapid test (InBios) are FDA cleared, but comparative data in U.S. populations are sparse. We evaluated 500 seropositive and 300 seronegative blood donor plasma samples. Country of birth was known for 255 seropositive specimens, which were grouped into regions as follows: Mexico (n = 94), Central America (n = 88), and South America (n = 73). Specimens were tested by the four FDA-cleared IgG serological assays. Test performance was evaluated by two comparators and latent class analysis. InBios had the highest sensitivity (97.4% to 99.3%) but the lowest specificity (87.5% to 92.3%). Hemagen had the lowest sensitivity (88.0% to 92.0%) but high specificity (99.0% to 100.0%). The level of sensitivity was intermediate for Ortho (92.4% to 96.5%) and Wiener (94.0% to 97.1%); both had high specificity (98.8% to 100.0% and 96.7% to 99.3%, respectively). The levels of antibody reactivity and clinical sensitivity were lowest in donors from Mexico, intermediate in those from Central America, and highest in those from South America. Our findings provide an initial evidence base to improve laboratory diagnosis of Chagas disease in the United States. The best current testing algorithm would employ a high-sensitivity screening test followed by a high-specificity confirmatory test.

Keywords: Chagas disease; Trypanosoma cruzi; United States; blood donors; diagnostics; serology.

Figures

FIG 1
FIG 1
Distribution of positive serology values by blood donor region of birth. Results are expressed as signal over cutoff (S/CO) for Ortho, optical density at 450 nm for Hemagen and Wiener, and scores 0 to 6 for InBios. Across all tests, individuals born in Mexico showed the lowest test values and individuals born in South America the highest. ns, P > 0.05; *, P ≤ 0.05; **, P ≤ 0.01; ***, P ≤ 0.001; ****, P ≤ 0.0001.
FIG 2
FIG 2
Effects of variations in the clinical sensitivity of initial test in a two-step diagnostic algorithm. Two-step diagnostic algorithms allow an acceptable number of false positives to ensure that positive cases are detected. (A) Higher-sensitivity initial test, with a high-specificity confirmatory test to rule out false positives. (B) Missed case of Chagas disease due to a lower-sensitivity initial test and false-negative result.

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