Diagnostics & Imaging Week Daily

The FDA last week reported that it has approved a new test to screen blood donors for a blood-borne parasite that causes Chagas disease, a tropical disease that is carried by the parasite Trupanosoma cruzi and spread by the so-called "kissing" bug – among other names – or technically triatomine bugs.

Also called American trypanosomiasis, according to the Centers for Disease Control and Prevention (Atlanta), the disease is commonly found in parts of Mexico, Central and South America. As transplants from those areas have moved into the U.S., the bugs have moved with them and the parasite has been on the increase among blood donors in the U.S.

"Our blood supply is now extremely safe from diseases once frequently transmitted by blood, such as HIV. However, we are constantly faced with new threats," said Jesse Goodman, MD, director of the FDA's Center for Biologics Evaluation and Research (CBER). "Evaluating this test involved a high degree of interaction between FDA scientists, the blood industry and the test developers. It is part of an ongoing effort to, wherever possible, identify emerging threats and provide the tools needed to help keep blood safe."

It is estimated that as many as 11 million people are currently infected by T. cruzi, primarily in the tropical regions mentioned. As the incidence of those infected with the parasite began to increase in recent years, the FDA's Blood Products Advisory Committee "asked manufacturers in 2002 to begin developing tests for Chagas," said Steve Dnistrian, VP for worldwide communications at Ortho-Clinical Diagnostics (Raritan, New Jersey), developer of the test.

"We began the process with R&D from scratch and . . . within four years we're on the market," Dnistrian told Diagnostics & Imaging Week. "We went through an extensive FDA process too, because it's a higher bar to pass on these types of tests."

Called the Ortho T. cruzi ELISA test, the product is the first such test for blood screening approved by the FDA.

The test is not yet FDA-approved to diagnoses Chagas in patients, but the company said it expects to go before the FDA seeking approval for this use, as well as use to detect Chagas in tissue and cell transplants, in 2007.

"Data reported over the past decade indicate a strong upward trend in the proportion of U.S. blood donors testing positive for exposure to the parasite that can cause Chagas disease," said Michael Waller, MD, VP, clinical and medical affairs, Ortho-Clinical Diagnostics.

A study conducted in the same geographic area of the U.S. showed a ratio of sero-positive blood donors ranging from 1 positive in 9,900 in 1996, to 1 in 7,200 in 1997, to 1 in 5,400 in 1998, Ortho-Clinical said.

A new study completed in November, Ortho-Clinical said, "documents" the ratio of Chagas-seropositive blood donors at about 1 in 2,000.

"FDA . . . did ask for an additional real-time read on positives in the blood supply," Dnistrian said.

The company said that in its clinical trials, the test demonstrated 100% sensitivity to all geographic strains test of Chagas disease. The test demonstrated an observed specificity of 99.99%.

The test is fully automated and is a menu addition for the company's Ortho Summit System. The company said it will begin production of the test immediately and soon will have "sufficient production capacity to meet the needs of blood banks nationwide."

Ortho-Clinical said that more than 15 million units of blood are donated each year in the U.S. currently. About 38,000 pints of blood are used every day in a variety of medical procedures, and those donations are currently screened for hepatitis, HIV and HTLV, or Human T-lymphotropic virus. The company said that in December 2005, the FDA approved a blood-screening test for West Nile virus. In 2003, it approved a general diagnostic test for West Nile.

Unfortunately, however, most of those people infected show no symptoms. Transmission occurs through insect bites, blood transfusions, organ transplants and via infected pregnant women to children in utero.

According to the CDC, "Chagas can cause serious illness." It said that in its early stages, the infection is "not considered severe" and can be treated during the first, acute stage of the three stages of infection. Symptoms during this stage may include fatigue, fever, enlarged liver or spleen and swollen lymph glands. Sometimes these symptoms are accompanied by a rash, loss of appetite, diarrhea and vomiting.

The CDC said that in infants and very young children with acute Chagas disease, the brain "may be damaged severely enough to cause death."

While some people infected may never exhibit symptoms, others proceed through the "indeterminate" stage of eight to 10 weeks after infection on to the chronic stage in 10 to 30 or 40 years after infection.

At that point, people can develop what are considered the most serious symptoms of the disease, or cardiac problems, which may include everything from an enlarged heart to an altered heart rate, the CDC said. The disease can also cause enlargement of the esophagus or large bowel, which can result in problems with swallowing or severe constipation.

About 50,000 people annually are expected to die from the disease.