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Bacteria-tainted platelets focus of transfusion risks.

Always consider the possibility of bacterial contamination of blood products--particularly platelets--in patients who experience a febrile reaction to a transfusion, the Centers for Disease Control and Prevention advised.

Transfusion-associated bacterial sepsis is the second most frequently reported cause of transfusion-related mortality in the United States, accounting for 17% of 277 reported transfusion deaths during 1990-1998 (MMWR 2005;54:168-70).

Platelets are vulnerable to bacterial growth because they are stored at room temperature for up to 5 days, whereas other blood components are refrigerated or frozen. An estimated 1 in 1,000-3,000 platelet units are contaminated with bacteria, resulting in life-threatening sepsis in 1 of every 100,000 transfusion recipients and immediate death in 1 of every 500,000 recipients.

These risks are greater than those estimated for transfusion-associated viral infections such as hepatitis C virus or HIV--yet are still likely to be underestimates because bacterial infections attributed to contaminated platelets are underreported, the CDC said.

To reduce this risk, AABB (formerly the American Association of Blood Banks), adopted a new standard in March 2004, requiring member blood banks and transfusion services to implement measures to detect and limit bacterial contamination in all platelet components.

A survey conducted last summer by the Infectious Diseases Society of America (IDSA) suggested that awareness of the problem and new standard was not high.

The survey was distributed to all 870 infectious-disease consultant members of IDSA's Emerging Infections Network. Of the 399 who responded, only 36% reported being aware that bacterial contamination of platelets was one of the most common infection risks of transfusion therapy, and only 20% indicated having been familiar with the new AABB standard prior to participating in the survey.

The CDC cited two case reports that illustrate the need for awareness and rapid diagnosis of transfusion-associated infections, since false negatives--leading to fatal bacterial sepsis--can occur even when pretransfusion testing complies with the new standard.

In one case, a 74-year-old man with leukemia died of sepsis 21 days after receiving a transfusion consisting of a pool of five platelet unit concentrates. Before transfusion, the pooled unit had been tested with a reagent strip to determine the pH level, a means for detecting the presence of bacteria. Despite the sample having been within the accepted range (pH greater than 6.4), the patient's blood cultures following transfusion grew Staphylococcus aureus.

Although the use of pH tests are an option under the AABB standard, they are less sensitive than are culture-based methods in whole-blood-derived samples, which are pooled from multiple donors. However, because culture-based tests are logistically difficult and costly to implement for whole-blood-derived platelets, most blood collection centers only culture apheresis platelets, which are derived from single donors, the CDC explained.

But culture had been performed in the second case, a 79-year-old man who received a transfusion of pheresis platelets for thrombocytopenia after coronary artery bypass surgery. Nonetheless, he developed shortness of breath, chills, a fever, and hypotension about an hour after the transfusion, experienced multiple thrombotic events, and died 27 hours later. Staphylococcus lugdunensis was later cultured from his blood and the leftover platelet bag.

Here, the volume of the platelet sample--4 mL in a standard aerobic blood culture bottle--was less than the manufacturer's recommended volume for platelet screening.


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Title Annotation:Clinical Rounds
Author:Tucker, Miriam E.
Publication:OB GYN News
Date:Apr 1, 2005
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