How to Test for Chagas Disease
Screen all patients from Latin American endemic areas using two different serological tests (IHA, IFA, or ELISA), and confirm positive results with a second test using a different methodology. 1
Who Should Be Screened
Screening is indicated for:
- All persons from endemic areas in Latin America (21 countries from southern United States to northern Argentina and Chile) 1
- Children born to mothers from endemic areas (vertical transmission screening) 1
- Persons with family members diagnosed with Chagas disease 2
- Persons who have lived in homes of natural material in Latin America 2
- Persons with history of kissing bug bites 2
- Blood and organ donors from endemic regions 1
The highest prevalence is found among Bolivian immigrants (10-40%), making this population particularly important to screen 1
Diagnostic Approach by Clinical Phase
Acute Phase (First 1-2 Months After Infection)
- Direct parasite detection through concentration test or microscopy 3
- This method is most useful in infants <8 months of age 3
- Serological tests may be negative early in acute infection 4
Chronic Phase (Most Common Presentation in Migrants)
Two-test serological strategy is mandatory:
- Use at least two different conventional serological tests from: 1, 5
- Indirect hemagglutination assay (IHA)
- Immunofluorescence antibody assay (IFA)
- Enzyme-linked immunosorbent assay (ELISA)
- Both tests must be positive to confirm diagnosis 5, 3
Nonconventional assays for treatment monitoring:
- F29-ELISA (detects antibodies against recombinant flagellar antigens) 5, 3
- AT-chemiluminescence-ELISA 5
- These are used to assess treatment response, not for initial diagnosis 5, 3
Critical Testing Pitfalls to Avoid
Do not rely on a single serological test - false positives can occur with leishmaniasis and other parasitic infections, requiring confirmation with a second test using different methodology 1
In endemic areas versus non-endemic areas:
- Endemic areas: Direct parasite identification is feasible during acute phase 4
- Non-endemic areas (Europe, North America): Diagnosis relies almost exclusively on serological testing since most cases are chronic and asymptomatic 4
Baseline Evaluation After Positive Serology
Once Chagas infection is confirmed, assess for organ involvement:
Cardiac evaluation (mandatory for all positive patients): 1, 6
- 12-lead electrocardiogram (look for right bundle-branch block, left anterior fascicular block, complete AV block)
- Echocardiogram (assess for biventricular enlargement, wall thinning, apical aneurysms, mural thrombi)
- Cardiac involvement occurs in 19% of infected individuals 1, 4
Gastrointestinal evaluation (if symptomatic): 6
- Esophageal manometry
- Barium swallow
- Barium enema
- GI involvement occurs in approximately 5% of infected individuals 4
Special Population Considerations
Pregnant women from endemic areas:
- Screen during pregnancy to identify risk of vertical transmission 1
- Vertical transmission occurs in 3 of 100 live births 1
- Test newborns of infected mothers at birth and again after 8 months of age 3
Children <8 months:
- Use direct parasite detection methods (concentration test) 3
- Serological tests may reflect maternal antibodies rather than infant infection 3
Children ≥8 months to <18 years:
- Require positive results on both lysate ELISA and recombinant ELISA for diagnosis 3
The quality of evidence for screening strategies is generally low due to heterogeneity in studied populations, but the recommendation to screen high-risk groups is strong given the significant morbidity (30-40% develop chronic complications) and mortality associated with untreated disease 1