Risk of transfusion-transmitted Babesia microti in Canada.

BACKGROUND: Babesia microti has gained a foothold in Canada as tick vectors become established in broader geographic areas. B. microti infection is associated with mild or no symptoms in healthy individuals but is transfusion-transmissible and can be fatal in immunocompromised individuals. This is the first estimate of clinically significant transfusion-transmitted babesiosis (TTB) risk in Canada. STUDY DESIGN AND METHODS: The proportion of B. microti-antibody (AB)/nucleic acid amplification test (NAT)-positive whole blood donations was estimated at 5.5% of the proportion of the general population with reported Lyme Disease (also tick-borne) based on US data. Monte Carlo simulation estimated the number and proportion of infectious red cell units for three scenarios: base, localized incidence (risk in Manitoba only), and donor study informed (prevalence from donor data). The model simulated 1,029,800 donations repeated 100,000 times for each. RESULTS: In the base scenario 0.5 (0.01, 1.75), B. microti-NAT-positive donations would be expected per year, with 0.08 (0, 0.38) recipients suffering clinically significant TTB (1 every 12.5 years). In the localized incidence scenario, there were 0.21(0, 0.7) B. microti-NAT-positive donations, with 0.04 (0, 0.14) recipient infections (about 1 every 25 years). In the donor study informed scenario, there were 4.6 (0.3, 15.8) B. microti-NAT-positive donations expected, and 0.81 (0.05, 3.14) clinically significant TTB cases per year. DISCUSSION: The likelihood of clinically relevant TTB is low. Testing would have very little utility in Canada at this time. Ongoing pathogen surveillance in tick vectors is important as B. microti prevalence appears to be slowly increasing in Canada.

Quality of red blood cells washed using the ACP 215 cell processor: assessment of optimal pre- and postwash storage times and conditions.

BACKGROUND: Washing of red blood cell concentrates (RCCs) is required for potassium-sensitive transfusion recipients, including neonates in need of large-volume transfusions. When open, nonsterile washing systems are used, postwash outdate time is limited to 24 hours, often leading to problems providing the component to the patient before expiry. STUDY DESIGN AND METHODS: A closed, automated cell processor, the ACP 215 from Haemonetics Corporation, was used to wash RCCs and determine optimal pre- and postwash storage times. Two postwash storage solutions, additive solution (AS)-3 and saline-adenine-glucose-mannitol (SAGM), were compared. The in vitro quality of leukoreduced RCCs, prepared from citrate-phosphate-dextrose-anticoagulated whole blood, was determined postwash and compared to existing guidelines for RCC quality (hemoglobin content, hematocrit, and hemolysis) and predetermined criteria for ATP and supernatant potassium levels. A criterion for visual hemolysis was also applied. RESULTS: The prewash storage time, postwash storage time, and the postwash resuspension solution all contributed to RCC quality postwash. Levels of hemolysis were greater when washed RCCs were resuspended in SAGM (p = 0.01), while AS-3 proved worse at maintaining ATP levels postwash (p < 0.01). Immediately postwash, all units had supernatant K+ levels below the detection limit of the instrument (<1 mmol/L), but these increased to above acceptable levels within 14 days. CONCLUSION: Based on all acceptance criteria, a maximum 14-day prewash storage period and 7-day postwash storage period in SAGM preservative was found to be optimal. The longer outdate time postwashing should help lessen challenges in providing components to patients before expiry.

Evaluating the 4-hour and 30-minute rules: effects of room temperature exposure on red blood cell quality and bacterial growth.

BACKGROUND: A 30-minute rule was established to limit red blood cell (RBC) exposure to uncontrolled temperatures during storage and transportation. Also, RBC units issued for transfusion should not remain at room temperature (RT) for more than 4 hours (4-hour rule). This study was aimed at determining if single or multiple RT exposures affect RBC quality and/or promote bacterial growth. STUDY DESIGN AND METHODS: Growth and RT exposure experiments were performed in RBCs inoculated with Serratia liquefaciens and Serratia marcescens. RBCs were exposed once to RT for 5 hours (S. liquefaciens) or five times to RT for 30 minutes (S. marcescens) with periodic sampling for bacterial counts. Noncontaminated units were exposed to RT once (5 hr) or five times (30 min each) and sampled to measure in vitro quality variables. RBC core temperature was monitored using mock units with temperature loggers. Growth and RT exposure experiments were repeated three and at least six times, respectively. Statistical analysis was done using mixed-model analysis. RESULTS: RBC core temperature ranged from 7.3 to 11.6°C during 30-minute RT exposures and the time to reach 10°C varied from 22 to 55 minutes during 5-hour RT exposures. RBC quality was preserved after single or multiple RT exposures. Increased growth of S. liquefaciens was only observed after 2 hours of continuous RT exposure. S. marcescens concentration increased significantly in multiple-exposed units compared to the controls but did not reach clinically important levels. CONCLUSION: Single or multiple RT exposures did not affect RBC quality but slightly promoted bacterial growth in contaminated units. The clinical significance of these results remains unclear and needs further investigation.

Transfusion reactions: a comparative observational study of blood components produced before and after implementation of semiautomated production from whole blood.

BACKGROUND: A semiautomated method of component production from whole blood was implemented at Canadian Blood Services. To assess safety of the new components, the frequency of adverse transfusion events (ATEs) to platelet components (PCs) and red blood cell (RBCs) produced before and after implementation of the new method was surveyed and compared. STUDY DESIGN AND METHODS: This retrospective, observational, noninferiority study was conducted in 12 sentinel hospitals across Canada. The control group received RBCs in additive solution-3 (AS-3) and platelet-rich plasma (PRP)-produced platelets (PLTs) for 3 to 11 months before implementation of semiautomated production, and the study group received RBCs in saline-adenine-glucose-mannitol (SAGM) and buffy coat (BC)-produced PLTs for 3 to 11 months after implementation. ATE definitions at each hospital and standard practice for reporting did not change between control and study periods. Data for analysis were obtained from databases and original report forms. RESULTS: The pooled risk ratio of a reaction to SAGM versus AS-3 RBCs was 0.77 (95% confidence interval [CI], 0.66-0.90), suggesting that SAGM products had significantly lower reaction rates than AS-3 products (p < 0.01). Reported allergic reactions to RBCs decreased from 0.07% (AS-3) to 0.04% (SAGM). For PLTs, the difference in reaction rates between BC and PRP was not significant (p = 0.37), and the pooled risk ratio of BC versus PRP was 1.14 (95% CI, 0.86-1.50). CONCLUSION: The change in manufacturing method was associated with lower reaction rates to SAGM RBCs than to AS-3 RBCs. Pooled BC PLTs were noninferior to random-donor PRP PLTs with respect to ATEs.

Assessment of a travel question to identify donors with risk of Trypanosoma cruzi: operational validity and field testing.

BACKGROUND: Because Trypanosoma cruzi (T. cruzi) infection in Canada and the United States is largely contracted in endemic countries, targeted testing of blood donors with risk travel may improve safety. The operational validity of a travel question suitable for donor screening was tested, and it was field-tested. STUDY DESIGN AND METHODS: After 1331 donors completed a short travel question, operational validity was assessed by detailed travel histories in face-to-face interviews. Two nationwide donor surveys were carried out assessing donor responses to similar travel questions in 2001 (13,623 donors) and in 2006 (20,037 donors). All donors in Toronto, Ontario, answered a travel question in 1997 and those born in or who spent 6 months or more in Mexico, Central America, or South America were tested for antibody to T. cruzi. RESULTS: There was 97.3 percent agreement between the travel question and detailed interviews, with 15 donors (1.1%) failing to acknowledge risk travel (false-negative questioning responses). Of these, 6 donors were born there and 7 others had less than 1 year of cumulative travel. In 2001 and 2006, there were 2.1 and 2.0 percent of donors with risk travel, respectively, but 16.5 and 11.2 percent of these donors were identified only because they were born there (travel not acknowledge). There were 1337 (1.6%) donors in Toronto in 1997 with risk travel and none were positive for the presence of T. cruzi antibody. CONCLUSION: Donors can answer a short question about cumulative time in Latin America with similar accuracy to detailed questioning, but screening questions should also include country of birth.

The donor health assessment questionnaire: potential for format change and computer-assisted self-interviews to improve donor attention.

BACKGROUND: The Canadian donor health assessment questionnaire (DHAQ) has developed gradually over many years. The purpose of this study was to determine whether the format and method of administration of the DHAQ influences donor attentiveness. STUDY DESIGN AND METHODS: Between May 2004 and September 2005, a total of 1,397 donors participated in the study by completing the DHAQ by one of three methods: the current Canadian Blood Services (CBS) format and method of administration, which is partly self-administered and partly interviewer-administered (Method 1); the DHAQ reformatted to the AABB Uniform Donor Health Questionnaire format and self-administered (Method 2); and an audiovisual computer-assisted self-interview (CASI; Method 3). This was followed by a short, scripted interview assessing recall of 17 specific items queried on the DHAQ. Time to completion of the DHAQ and degree of familiarity with computer use were also assessed. RESULTS: The percentages of donors identifying all 17 items correctly were 9.4, 20.9, and 34.8 percent and the mean percentages recall of items were 53.9, 56.0, and 69.8 percent with DHAQ administration Methods 1, 2, and 3, respectively (p < 0.0001). This difference was largely attributable to the poor recall of items queried as part of a list in Method 1. Mean times to complete the DHAQ were 3.1, 3.8, and 8.1 minutes for Methods 1, 2, and 3, respectively. More than 95 percent of donors had used a personal computer in the past year. CONCLUSION: The current format of the Canadian DHAQ is not optimal for donor attention to specific questions asked as part of a list. Attention was improved by use of AABB uniform donor history questionnaire format and was best with use of a CASI format.

The Canadian donor health assessment questionnaire: can it be improved?

BACKGROUND: The donor health assessment questionnaire (DHAQ) plays an important role in ensuring blood safety. The Canadian DHAQ has been developed over many years on an ad hoc basis and has never been evaluated in light of cognitive science principles. In addition, donor attitudes about its mode of administration have not been assessed. STUDY DESIGN AND METHODS: Between May and August 2005, a total of 456 donors participated in the study by completing the DHAQ, followed by a short, scripted interview assessing recall (as an indicator of attention to the questions) of 17 specific items queried on the DHAQ and attitudes toward interviewer or self-administration of the DHAQ. RESULTS: Overall, 7.5 percent of donors were able to correctly identify all 17 items. Recall was best for questions asked as individual items (87%-99%) and decreased substantially for items that are part of a list (55%-91%). Position effects were demonstrated, with items at the end of a list being the most frequently forgotten. Twenty percent of repeat donors favored the current practice of interviewer administration of high-risk questions, whereas 80 percent were neutral or favored self-administration. CONCLUSION: The current format of the Canadian DHAQ is not optimal for donor attention to specific questions asked as part of a list. The majority of repeat donors are ready for a change in the method of administration of the DHAQ. Studies on donor recall may help guide evidence-based changes to the DHAQ.