Laboratory Diagnosis
Laboratory diagnosis of acute Chagas disease can be made via microscopic identification of T. cruzi in blood smears or detection of T. cruzi DNA by polymerase chain reaction (PCR). Prior to collecting diagnostic specimens for the diagnosis of acute Chagas disease (i.e. in neonates born to a Chagas-positive mother; in recipients of organs or blood from a Chagas-positive donor; in lab/occupational exposures; and in persons with confirmed exposure to a T. cruzi-infected triatomine bug), clinicians should consult with DSHS Regional Zoonosis Control (ZC) program staff to discuss testing options. Providers wishing to submit samples to CDC for molecular testing (PCR) must consult with the DSHS Regional Zoonosis Control (ZC) program before sample submission.
Laboratory diagnosis of chronic Chagas disease is based upon serologic testing. Because no currently-available serologic test is sensitive or specific enough to confirm a diagnosis, two different format serologic tests which use different parasite antigen preparations to detect T. cruzi-specific antibody are used to determine infection status. If you wish to test a patient for Chagas disease, please note the following:
- CDC will not accept serologic specimens for initial screening for chronic Chagas disease. Serologic screening should first be performed at the DSHS laboratory or one of the commercial laboratories which offer testing.
- Patients testing positive at a commercial lab should have additional testing at the DSHS laboratory; all samples testing positive, equivocal, or inconclusive at DSHS will be forwarded to CDC for confirmatory testing provided there is sufficient sample volume available.
Laboratory testing recommendations for Chagas disease can be complex. The DSHS Chagas Disease Exposure Assessment and Testing Guide and list of Major Laboratories that Currently Perform Trypanosoma cruzi Testing may be helpful.
Blood Donor Testing
Blood banks screen first-time blood donors for evidence of T. cruzi infection. Donors testing positive are notified by the blood bank and are advised to consult their medical provider for additional laboratory testing and clinical evaluation. Blood donor screening tests are not suitable for confirmation of clinical diagnosis. Blood donors who receive a letter stating that they tested positive for Chagas disease should have serum tested at the DSHS laboratory or a commercial laboratory.
Clinical Evaluation of Laboratory-Diagnosed Patients
For patients with confirmatory laboratory testing for Chagas disease, medical providers should obtain a thorough history to evaluate potential routes of exposure, travel to or residence in areas endemic for human disease, previous history of blood transfusions or organ/tissue transplants, and the possibility of maternal transmission. Baseline clinical workup should include a complete physical exam and a 12-lead ECG with a 30-second lead II rhythm strip. Additional cardiac and gastrointestinal studies may be performed if indicated by the patient’s symptoms or clinical signs. Evaluation and testing of household contacts may be indicated for those sharing similar risk profiles and is strongly recommended if maternal transmission is a possibility, either from the index case or to the index case. Patients should be counseled not to donate blood or tissues for the remainder of their lifetime.
Treatment
Antiparasitic treatment is indicated for all acute infections, for chronic infections in children up to 18 years of age, for chronic infection in adults up to age 50 who have no indication of advanced cardiomyopathy, and for reactivated infections in immunocompromised patients. The decision to treat patients over age 50 years who do not have advanced cardiomyopathy should be made weighing the potential benefits and risks for the individual patient. CDC consultation is available to assist with management of patients with Chagas disease [parasites@cdc.gov, (404) 718-4745].
Two drugs—benznidazole and nifurtimox—are available for treatment of U.S. patients. Benznidazole has been approved by the U.S. Food and Drug Administration (FDA) for use in children 2-12 years of age, although it may be used “off-label” for other age groups. Nifurtimox (Lampit®) has been FDA approved for use in children from birth to 17 years of age. Both drugs may cause significant side effects that some patients may not tolerate.
Continuing Medical Education
Chagas disease CME is available via an online course offered on the CDC Chagas disease website.