Should at-risk donors be interviewed and/or tested for T. cruzi infection to prevent transfusion-transmitted Chagas Disease?

Trypanosoma cruzi (T. cruzi) is a protozoan parasite that causes Chagas disease (CDC Fact Sheets). Estimates suggest that as many as 18 million people are infected world-wide, mainly in Central and South America, and that the infection causes up to 50,000 deaths per year. The usual route of infection in humans is via the bite of an infected insect, but transmission by transfusion or transplantation, and perinatal infection from mother to child also occur. An e-network forum member has asked about the extent that donors should be interviewed and/or tested for risk of T. cruzi infection. For more details on this issue, please see the following discussions:

Chagas Disease Found in Three Organ Transplant Recipients - Priorities for testing blood donors?

Should Blood Donors Be Asked About Chagas Disease Risk Behavior?

The following responses were received.

ADDENDA June 12, 2002

1. A Project Manager at the FDA, CBER, OBRR, Division of Blood Resources wrote that regarding Chagas' disease, it is important to also note that Central and South America have done excellent jobs in their eradication efforts, as incident cases have declined by 90% or greater in many of these countries over the past 10 years. While prevalent cases are still a concern, the FDA staffer wanted to be sure that blood bankers are aware of the eradiction efforts and results.

ADDENDA June 21, 2002

2. A blood banker in Los Angeles wrote that the blood banking community should be aware of a May 2002 publication (Leiby DA et al. Transfusion, Volume 42 Issue 5 Page 549 - May 2002) which reports that significant numbers of T. cruzi-seropositive donors contribute to the U.S. blood supply, and that the incidence of seropositivity is enhanced by minority recruitment efforts necessitated by donor demographic shifts. Similarly, high rates among directed donations in Los Angeles are attributable to a disproportionate number of at-risk directed donors. Current look-back data likely underestimate the frequency of transfusion- transmitted T. cruzi.

ADDENDA July 11, 2002

3. A transfusion service medical director who works in California expressed concern regarding the above discussion. He believes that in the Los Angeles basin there are quite a few donors who come from south of the Rio Grande, and while the blood banking community and others are all up in arms about Mad Cow Disease, the fact that blood infected with T. Cruzi is likely being transfused is not being adequately addressed. Knowing the incidence of Chagas in Los Angeles based blood donors, he wonders if it can be predicted how many recipients in the Los Angeles area are being infected with this parasite? He also wonders if these recipients should be warned of this risk when they are giving informed consent for transfusion.

ADDENDA Aug. 1, 2002

4. Editor's Note: Please visit this page for an earlier review on Chagas Disease by Dr. Leiby - on the ARC Northern California Region web site.

ADDENDA Sept. 3, 2002

5. Frank Boulton of the UK's National Blood Service writes:
   
   "For those who missed it, for a European view, see abstract number 92 of the poster session presented at the recent ISBT meeting in Vancouver, 2002 (text below)
   
   The former UK rule excluded virtually ANYONE who might have been exposed to the bugs during a visit to South or Central America. A lot of antibody tests were therefore requested. By being much more selective about exclusion, and applying the antibody test much more selectively, we believe that the situation has improved (for the UK and, by extension, Europe). Of course, T Cruzi is a low risk in the UK and does not feature heavily in terms of cost-efficacy; the situation in N America is different."

ADDENDA Nov 29, 2004

6. The Editor refers visitors to the following recent announcement about evaluation by Florida Blood Services of an investigational test for screening donors for the Chagas disease parasite.

ADDENDA Nov 30, 2004

7. A Senior Scientist in San Francisco has graciously shared data from his recent evaluation of a new ELISA for detection of Chagas antibody. See abstract (PDF) from the 2004 AABB Annual Meeting.

ADDENDA Feb. 19, 2007

8. Editors' note: The AABB Association Bulletin #06-08 - Chagas' Disease (AABB Membership required to access) and the case report: Young C, et al. Transfusion-acquired Trypanosoma cruzi infection are germane to the discussion.

ADDENDA Feb. 21, 2007

9. Iñigo Romon MD, PhD, Quality Manager for the Blood and Tissues Bank of Cantabria in Santander, Spain (attribution used with permission) reports that the following information regarding their experience with a strategy for T. cruzi screening of blood donations will be presented at an upcoming ISBT meeting.

He writes:

"BACKGROUND:
According to Spanish regulations, potential donors born, or children of women born in T. cruzi endemic areas, must test negative for a validated test directed at the detection of carriers, in order to qualify as donors. Our Blood Center implemented this strategy in June 2006, including an additional group of donors at risk, comprising those who have spent more than a month in endemic areas.

METHODS:
We use ID PaGIA Chagas Antibody test (DiaMed) as a screening test. We include positive and negative controls in every test batch. The test is performed before donation, and donors are accepted if the result is negative. Confirmatory tests of positive samples (ELISA, IFI, PCR) are performed at the national reference laboratory (Instituto de Salud Carlos III). Results are communicated by post and positive donors are counselled at an interview with the Donor Center physician.

RESULTS: between June 2006 and December 2006, 14676 prospective donors visited our facility. 133 (0.9%) were considered to be at risk. Tables 1 and 2 describe donor’s characteristics.

Table 1: Risk factors

Table 2: Country of origin

2 of the 133 samples (1.5%) were positive at screening.

The first of case was confirmed by ELISA, IFI and PCR. The donor is a 62 year old woman born in Venezuela who remains asymptomatic, but her EKG shows conduction anomalies and has been put under clinical surveillance.

The second case had lived in Argentina, and the confirmatory tests were negative. She is under clinical follow up.

Of the 131 donors who tested negative (98.5% of screened donors), 88 (67%) have not come back for donation. 38 donated (29%) and 5 tried to donate but were rejected for other reasons.

CONCLUSIONS: In our setting, 1.8% of the population and 0.9% of our donors come from Central or South American stock. We consider that our screening strategy is satisfactory because of its simplicity and its reproducibility compared with a validated diagnostic test (1.5% of positive, 0.7% not confirmed). It is remarkable that only 33% of those potential donors who were initially deferred have tried to donate again."

He acknowledges that they must implement strategies to recruit more donors to overcome the loss of donors imposed by new regulations.

ADDENDA Feb. 24, 2007

10. Editors' note: The information at MMWR: Blood Donor Screening for Chagas Disease: United States, 2006-2007 is germane to this discussion.

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Ira A. Shulman, MD
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Elizabeth M. St. Lezin, MD
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