# Diagnosis of Trypanosoma cruzi infection in Mexican populations: current conventional serology lacks adequate sensitivity and specificity

## TL;DR

This study shows that current blood tests for Trypanosoma cruzi in Mexico are not reliable and suggests using molecular methods for better diagnosis.

## Contribution

The study evaluates diagnostic performance in specific ethnic populations and highlights the inadequacy of conventional serology.

## Key findings

- Only 81% of previously diagnosed infections were reconfirmed using serology.
- Serological sensitivity was 8% and specificity 16% in the primary diagnosis cohort.
- Molecular testing identified T. cruzi and T. dionisii co-infections using 18S ribosomal DNA.

## Abstract

The performance of serological tests for Trypanosoma cruzi
diagnosis in Mexico has not included discordant control sera nor has it
evaluated the role of immune response specificities, patient infection
history or clinical status.

The performance of commercial serological and molecular diagnostic tests and
diagnostic algorithms was analysed in Mixtecan and Zapotecan ethnic
populations having recent and long-term infection history.

An amplified global gold standard for T. cruzi infection
included serological (≥ 2 conventional tests positive) and molecular
(sequence identity of any of five genes using end point polymerase chain
reaction (epPCR) or any positive using quantitative polymerase chain
reaction (qPCR) diagnostic test results.

Only 81% of previously diagnosed untreated infections were reconfirmed using
serology, while an additional 14% only using PCR. Serological diagnosis
sensitivity (≥ 2 tests positive) in the primary diagnosis cohort was 8%,
while specificity was 16%. Diagnosis sensitivity was similar using epPCR and
qPCR only in primary diagnoses and all identified using the satellite (SAT)
gene. The 18S ribosomal DNA identified T. cruzi and
T. dionisii co-infections from Pacific coast sites.

The current study provides evidence for inadequate diagnostic performance of
conventional serological tests and the need to develop appropriate antigenic
tools and use molecular testing of seronegatives to ascertain absence of
infection.