The newly approved test for antibodies to Trypanosoma cruzi, the parasite that causes Chagas' disease (American trypanosomiasis) joins a battery of automated tests performed by the ABBOTT PRISM system (Abbottdiagnostics.co.uk), already in use in more than 30 countries (Press release: “Abbott Receives FDA Approval for First Fully Automated Blood Test for ‘Kissing Bug’ Disease,” Abbott.com). Abbott Diagnostics, based in Illinois, describes the technology as “an instrument designed with, and for the transfusion industry.”
Chagas' Disease in Donor Blood and Organs
Trypanosoma cruzi is usually transmitted to humans by species of triatomine bugs, or kissing bugs. The bugs bite, drawing a blood meal, and then contaminate the bite lesion with their feces, which contain the protozoan parasite. Historically, the people most at risk were the South American poor, who live in rough housing where bugs can hide in thatch and crevices and venture out at night to feed.
The CDC Traveler’s Health – Yellow Book (Chapter 5, Cdc.gov) puts the number of people infected at 7.6 million, most of them in Mexico, Central America, and South America. Many people are unaware that they harbour a parasite that can cause serious health problems and even kill.
The advent of blood transfusions gave T. cruzi another way to spread from person to person – undetected in donor blood, the parasites infect blood recipients in South America and, increasingly, in other countries where immigrants from South America have settled. There has been a need for a sensitive, high volume test for blood units for years, especially in South American countries where a high percentage of units may test positive. In recent years, transmission of Chagas to both blood and donor organ recipients in the United States has prompted routine screening of donor samples.
Chemiluminescence Immunoassay Technology
Abbotts PRISM system uses chemiluminescence immunoassay technology to detect human antibodies to T. cruzi in a blood sample (Abbottdiagnostics.co.uk). Briefly, a chemical reaction emits light through the release of photons after antibodies in the sample have bound to a specific antigen. Detection of light indicates that antibodies are present, and that the donor has been exposed to T. cruzi.
The PRISM system also uses chemiluminescence to detect antibodies to HIV, hepatitis B, hepatitis C, and HTLV in human samples. The instrument is automated and can process 160 samples per hour, making it a highly efficient screening tool for laboratories processing large numbers of donor units.
Diagnosis of Chagas' Disease
Designed primarily for screening blood donated for transfusion, Abbott’s new test is unlikely to be used for routine diagnosis, though it will likely reveal considerable numbers of undiagnosed infections. Older antibody detection tests will remain the mainstay of diagnosis of American trypanosomiasis.
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Rosemary Drisdelle - Rosemary Drisdelle has been published many times as a nonfiction writer and several times as a poet. Her first book, Parasites: Tales of ...
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