Epidemiology of Hepatitis C over 28 years of monitoring Canadian blood donors: Insight into a low-risk undiagnosed population.

BACKGROUND: Hepatitis C is a blood-borne infection with the hepatitis C virus (HCV) that can progress to cirrhosis and liver cancer. About 70% (50-80%) of infections become chronic and exhibit anti-HCV and HCV nucleic acid (NAT) positivity. Direct acting oral pan genotypic antiviral treatment became available in 2014 and was free for most Canadians in 2018. Clinical screening for HCV infection is risk-based. About 1% of Canadians have been infected with HCV, with 0.5% chronically infected (about 25% unaware) disproportionately impacting marginalized groups. Blood donors are in good health, are deferred for risks such as injection drug use and can provide insight into the low-risk undiagnosed population. Here we describe HCV epidemiology in first-time blood donors over 28 years of monitoring. METHODS: All first-time blood donors in all Canadian provinces except Quebec (1993 to 2021) were analyzed. All blood donations were tested for HCV antibodies (anti-HCV) and since late 1999 also HCV NAT. A case-control study was also included. All HCV positive donors (cases) since 2005 and HCV negative donors (1:4 ratio controls) matched for age, sex and location were invited to complete a risk factor interview. Separate logistic regression models for anti-HCV positivity and chronic HCV assessed the association between age cohort, sex, region and neighbourhood material deprivation and ethnocultural concentration. CASE: control data were analysed by logistic regression. RESULTS: There were 2,334,238 donors from 1993 to 2021 included. Prevalence for anti-HCV was 0.33% (0.30,0.37) in 1993 and 0.07% (0.05,0.09) in 2021 (p < 0.0001). In 2021 0.03% (0.01,0.04) had chronic HCV. Predictors for both anti-HCV positivity and chronic HCV were similar, for chronic HCV were male sex (OR 1.8, 1.6,2.1), birth between 1945 and 1975 (OR 7.1, 5.9,8.5), living in the western provinces (OR 1.4, 1.2,1.7) and living in material deprived (OR 2.7, 2.1,3.5) and more ethnocultural concentrated neighbourhoods (OR 1.8, 1.3,2.5). There were 318 (35.4%) of chronic HCV positive and 1272 (39.6%) of controls who participated in case control interviews. The strongest risks for acquisition were injection drug use (OR 96.9, 22.3,420.3) and birth in a high prevalence country (OR 24.5, 11.2,53.6). CONCLUSIONS: Blood donors have 16 times lower HCV prevalence then the general population. Donors largely mirror population trends and highlight the ongoing prevalence of untreated infections in groups without obvious risks for acquisition missed by risk-based patient screening.

Prevalence of human T-cell lymphotropic virus-1/2 in Canada over 33 years: A unique contribution of blood donors to public health surveillance.

OBJECTIVES: Estimate HTLV-1/2 (human T-cell lymphotropic viruses) prevalence in Canadian blood donors and the association of demographic variables with infection and their corresponding risk factors. METHODS: First-time blood donors in all Canadian provinces (except Quebec) from 1990 to 2022 were included. Blood samples were tested for HTLV-1/2 by enzyme-linked immunoassay, confirmed by Western blot. Multivariable logistic regression with year, age group, sex, region, neighbourhood material deprivation, and ethnocultural composition indices predicted HTLV-1/2. Since 2005, all HTLV-1/2-positive donors (cases) were invited to participate in a risk factor interview, and 4 non-positive donors (controls per case) were matched for age, sex, and region. Case-control predictors of HTLV-1/2 were analyzed using logistic regression. RESULTS: There were 3,085,554 first-time donors from 1990 to 2022. HTLV-1/2 prevalence remained low (12 per 100,000 in 2022, 95% CI 6.4-23.5). The odds ratios predicting HTLV-1/2 were higher in females (2.0, 95% CI 1.5-2.6), older age groups (50 + ; 6.3, 95% CI 4.3-9.2), British Columbia and Ontario, those materially deprived (1.9, 95% CI 1.2-2.9), and those in ethnocultural neighbourhoods (7.5, 95% CI 3.2-17.3). Most HTLV-1/2 in Ontario was HTLV-1, whereas in British Columbia half were HTLV-2. Forty-three of 149 (28.8%) cases and 172 of 413 (41.6%) controls completed an interview. The strongest predictor of HTLV-1/2 in case-control analysis was birth in a high-prevalence country (OR 39.8, 95% CI 7.8-204.3) but about 50% of HTLV-1 and 90% of HTLV-2 were Canadian-born. CONCLUSION: HTLV-1/2 prevalence is low in blood donors. High-prevalence country of birth accounts for about half of HTLV-1; HTLV-2 positives are usually Canadian-born. HTLV-1/2 transmission likely occurs overseas and within Canada.

RéSUMé: OBJECTIFS: Estimer la prévalence des sous-types du virus T-lymphotrope humain (HTLV-1 et HTLV-2) dans le sang des donneurs de sang canadiens, et évaluer le lien avec des variables démographiques et des facteurs de risque donnés. MéTHODES: Cette étude a porté sur toutes les personnes ayant fait leur premier don entre 1990 et 2022 au Canada, sauf au Québec. Les échantillons de sang ont été soumis à un test immunoenzymatique, puis à un test Western Blot de confirmation. Les données ont été analysées au moyen de la régression logistique en utilisant comme indices l'année, la tranche d'âge, le sexe, la région, le quartier, la privation matérielle et la composition ethnoculturelle. Depuis 2005, tous les donneurs positifs au HTLV-1/2 (cas) ont été conviés à un entretien ayant pour but de déterminer leurs facteurs de risque, et quatre donneurs négatifs (cas-témoins) ont été appariés à chaque cas en fonction de l'âge, du sexe et de la région. Les facteurs de prédiction d'infection au HTLV-1/2 des cas-témoins ont été analysés au moyen de la régression logistique. RéSULTATS: Entre 1990 et 2022, le nombre de primodonneurs s'élevait à 3 085 554. La prévalence du HTLV-1/2 est demeurée faible (12,2 sur 100 000 en 2022, IC 95%: 6,4­23,5). Le rapport de cotes était plus élevé chez les femmes (2,0, IC 95% 1,5­2,6), chez les personnes de plus de 50 ans (6,3, IC 95% 4,3­9,2), en Colombie-Britannique et en Ontario, chez les personnes touchées par la privation matérielle (1,9, IC 95% 1,2­2,9) et chez les personnes vivant dans des quartiers ethnoculturels (7,5, IC 95% 3,2­17,3). La plupart des cas de HTLV-1/2 rencontrés en Ontario concernaient le HTLV-1, tandis qu'en Colombie-Britannique, la moitié des cas concernait le HTLV-2. Quarante-trois cas sur 149 (28,8 %) et 172 cas-témoins sur 413 (41,6 %) ont passé l'entretien. L'analyse des cas-témoins a révélé que le facteur de prédiction le plus important d'infection au HTLV-1/2 était le fait d'être né dans un pays à forte prévalence (RC 39,8, IC 95% 7,8­204,3); toutefois environ 50 % des cas-témoins de HTLV-1 et 90 % des cas témoins de HTLV-2 étaient nés au Canada. CONCLUSION: La prévalence du HTLV-1/2 est faible dans le sang des donneurs de sang. Pays de naissance à forte prévalence représente à peu près la moitié des cas de HTLV-1; les donneurs positifs au HTLV-2 la plupart du temps sont nés au Canada. La transmission du HTLV-1/2 survient probablement outre-mer et au Canada.

SARS-CoV-2 vaccination in Canadian blood donors: Insight into donor representativeness of the general population.

Introduction: Blood donors world-wide were indispensable for monitoring anti-SARS-CoV-2 antibodies generated by infection and vaccination during the pandemic. Prior to the pandemic, donor vaccination behaviours were under-studied. We aimed to compare the percentage of Canadian blood donors with SARS-CoV-2 vaccination antibodies with the percentage of the general population who received at least one dose of vaccine each month during initial vaccine deployment. We also report donor attitudes towards SARS-CoV-2 vaccination. Methods: Canadian blood donors were randomly selected for SARS-CoV-2 antibody testing over 2021 (N = 165,240). The percentage of donor samples with vaccination antibodies were compared with the percentage of general population who received at least one dose of vaccine in each month of 2021 except February. A random sample of Canadian blood donors were surveyed about vaccination intent and attitudes (N = 4,558 participated, 30.4 % response rate). Results: The percentages of the general population vaccinated and donors with vaccination antibodies increased from 1 % to over 90 %. General population vaccination was greater early in vaccine deployment than donors (p < 0.05), greater in donors than the general population by mid-2021 (p < 0.05) but they were similar by the end of 2021. While 52.6 % of surveyed donors had received vaccine in May 2021, a further 41.1 % intended to when eligible. Most donors thought COVID-19 infection could be serious (83.5 %) and that it was important to be vaccinated even if previously infected (77.8 %). Conclusion: Early pandemic vaccine prioritization to at-risk individuals and healthcare workers gave rise to higher general population vaccination percentages, while donors had higher vaccine antibody percentages as vaccine was deployed to progressively younger age groups. Since blood donors may be more willing to receive vaccination, under pandemic conditions they may be valuable for monitoring vaccination-induced seroprevalence.

Monitoring syphilis serology in blood donors: Is there utility as a surrogate marker of early transfusion transmissible infection behavioral risk?

BACKGROUND: In Canada the time deferral for gay, bisexual, and other men who have sex with men (gbMSM) was progressively shortened (lifetime, 5 years, 1 year, 3 months). Here we describe trends in syphilis rates (a potential sexual risk marker) and risk behaviors from blood donors in the past 12 years. STUDY DESIGN AND METHODS: Syphilis positivity in 10,288,322 whole blood donations (January 1, 2010-September 10, 2022) and gbMSM deferral time periods, donation status, age, and sex were analyzed with logistic regression. Overall, 26.9% syphilis positive and 42.2% controls (matched 1:4) participated in risk factor interviews analyzed by logistic regression. RESULTS: Syphilis rates were higher in first-time donors (OR 27.0, 95% CI 22.1-33.0), in males (OR 2.3, 1.9-2.8) and with the 3-month deferral (OR 3.4, 2.6-4.3) during which the increase was greater for first-time males (p < .001) but similar for male and female repeat donors (p > .05). Among first-time donors, histories of intravenous drug use (OR 11.7, 2.0-69.5), male-to-male sex 7.8 (2.0-30.2) and birth in a high prevalence country (OR 7.6, 4.4-13.0) predicted syphilis positivity; among repeat donors, history of male-to-male sex (OR 33.5, CI 3.5-317.0). All but 1 gbMSM syphilis-positive donors were noncompliant with the gbMSM deferral. About a quarter of first-time interviewed case donors had history of syphilis; 44% were born in a high-prevalence country. CONCLUSION: Rising syphilis rates in donors correlates with the general population epidemic. Recent infection rates rose similarly in males and females. GbMSM history may contribute to donor syphilis rates but shortening time deferrals appears unrelated.

Behaviour based screening questions and potential donation loss using the "for the assessment of individualised risk" screening criteria: A Canadian perspective.

BACKGROUND: To reduce the risk of HIV transmission through transfusion, gay, bisexual and other men who have sex with men (gbMSM) are deferred from donating blood in many countries for varying lengths of time after having sex with another man. In 2021, screening algorithms to identify high-risk sexual behaviours using gender-neutral criteria (i.e., without any question on MSM or time deferral for MSM) were implemented in the United Kingdom based on recommendations in a report from the FAIR (For the Assessment of Individualised Risk) steering group. OBJECTIVES: This study examines the potential donation loss expected with these criteria if implemented in Canada. METHODS: Responses from blood donors regarding engagement in behaviours such as chemsex and anal sex with a new or multiple partners within 3 months of donation were collected using an on-site paper questionnaire. RESULTS: Applying the FAIR criteria resulted in donation loss of 1.0% (95% CI: 0.8% - 1.1%). Donation loss would be higher amongst younger donors aged 17-25 (2.0%, 95% CI: 1.6% - 2.3%). Overall, 20% of donors reported feeling uncomfortable answering study questions but only 2.0% said it would stop them from donating. CONCLUSION: Donation loss could be compensated by newly eligible gbMSM and with increased recruitment and encouraging donation from infrequent donors.

HIV incidence and compliance with deferral criteria over three progressively shorter time deferrals for men who have sex with men in Canada.

BACKGROUND: In Canada, the deferral for men who have sex with men (MSM) has been progressively reduced from a permanent deferral for MSM since 1977, to 5 years, 1 year, and, most recently, 3 months. We estimated human immunodeficiency virus (HIV) residual risk and compliance with the MSM time deferral after each change. METHODS: Four anonymous online compliance surveys were carried out before and after each change. HIV incidence and prevalence were monitored from 2010 to 2021. Residual risk was estimated using the incidence-window period model. RESULTS: Human immunodeficiency virus prevalence, incidence, and residual risk did not change with incrementally shorter MSM deferrals. The residual risk per million donations post 3-month deferral was 0.05 (0.001-0.371). Men with temporally remote MSM history became eligible and, therefore, compliant as the deferral periods decreased (Cochran-Armitage p value = <.0001). However, the percentage of men with MSM history in the last 3 months with the indefinite deferral in place was similar to the percentage noncompliant, while the 3-month deferral was in place. MSM donors did not report high-risk behaviors for which they would otherwise be deferred in any survey. Following the change, an estimated 4467 MSM per year were eligible to donate, an increase from 2501 estimated eligible MSM donors following the change to the 1-year deferral. CONCLUSION: With progressively shorter MSM deferral periods, HIV residual risk was unchanged. The proportion of male donors with deferrable MSM history remained low, while those with temporally remote MSM history became eligible, increasing the number of eligible MSM donors.

Donor screening question alternatives to men who have sex with men time deferral: Potential impact on donor deferral and discomfort.

BACKGROUND: Alternative screening questions could permit low-risk men who have sex with men (MSM) to donate blood without a time deferral. We performed a study to determine the proportion of current donors who may be deferred by various questions and their comfort with them. STUDY DESIGN AND METHODS: Donors attending collection sites in Canada in January and February 2018 were offered one of two questionnaires but not both. Questionnaire 1 asked about risk behaviors; Questionnaire 2 rated comfort with the questions. Volunteers uncomfortable with questions participated in short qualitative telephone interviews to understand reasons. Quantitative data were analyzed using χ2 statistics. RESULTS: Of 36 241 donors attending, 31 904 (88%, Period 1) completed Questionnaire 1; of 34 947, a total of 30 278 (87%, Period 2) completed Questionnaire 2; 294 completed an interview. In the past 3 months 3.1% (95% confidence interval [CI], 3.1%-3.6%) had more than one partner; 6.0% (95% CI, 5.7%-6.2%) had a new partner; 6.7% (95% CI, 6.4%-6.9%) were in a nonexclusive relationship; 11.2% (95% CI, 10.9%-11.6%) had at least one of these; 3.7% (95% CI, 3.4%-3.9%) had anal sex; and 62.8% (95% CI, 62.2%-63.3%) had condomless sex. More than 6% were uncomfortable with each question, but more (17.2%; 95% CI, 16.8%-17.7%) were uncomfortable with anal sex. Key reasons for discomfort were questions being too personal and unclear safety benefit. CONCLUSION: Most donors are comfortable answering alternative questions (except very personal ones) but question the benefit. Implementing alternative questions would result in substantive deferrals. Other policies such as using an MSM capture question to ask additional questions only to MSM should be considered.

SARS-CoV-2 seroprevalence among blood donors after the first COVID-19 wave in Canada.

BACKGROUND: Case detection underestimates the burden of the COVID-19 pandemic. Following the first COVID-19 wave, we estimated the seroprevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) among blood donors across Canada. STUDY DESIGN AND METHODS: This serial cross-sectional study was conducted between May 9 and July 21, 2020 from blood donors donating at all Canadian Blood Services locations. We used the Abbott Architect assay to detect SARS-CoV-2 IgG antibodies from retention plasma. Seroprevalence was standardized to population-level demographics and assay characteristics were adjusted using the Rogan-Gladen equation. Results were stratified by region, age, ethnicity, ABO groups, and quantiles of material and social deprivation indices. Temporal trends were evaluated at 2-week intervals. Univariate and multivariate logistic regression compared SARS-CoV-2 reactive to non-reactive donors by sociodemographic variables. RESULTS: Overall 552/74642 donors, had detectable antibodies, adjusted seroprevalence was 7.0/1000 donors (95% CI; 6.3, 7.6). Prevalence was differential by geography, Ontario had the highest rate, 8.8/1000 donors (7.8, 9.8), compared to the Atlantic region 4.5/1000 donors (2.6, 6.4); adjusted odds ratio (aOR) 2.2 (1.5, 3.3). Donors that self-identified as an ethnic minority were more likely than white donors to be sero-reactive aOR 1.5 (1.2, 1.9). No temporal trends were observed. DISCUSSION: Worldwide, blood services have leveraged their operational capacity to inform public health. While >99% of Canadians did not show humoral evidence of past infection, we found regional variability and disparities by ethnicity. Seroprevalence studies will continue to play a pivotal role in evaluating public health policies by identifying trends and monitor disparities.

Compliance with time-based deferrals for men who have sex with men.

BACKGROUND: The deferral for men who have sex with men (MSM) was reduced from a permanent deferral for MSM if even one time since 1977 to progressively shorter time deferrals of 5 years and 1 year in Canada. We assessed compliance with these deferrals and the impact on safety at Canadian Blood Services. STUDY DESIGN AND METHODS: Three anonymous online compliance surveys of male whole blood donors were carried out before and after implementation of successive changes. HIV rates and incidence were monitored from January 1, 2011, to August 14, 2018. RESULTS: Participation rates in the consecutive surveys were 49.7% before implementation, 36.3% after 5 years and 36.3% after 1 year. There was no difference before versus after implementation in male donors with MSM history in the past year (0.21%, 0.19%, 0.24%; p = 0.70). The percentage of eligible MSM donors increased (0.13%, 0.66%, 1.21%; p < 0.0001), with approximately 2500 eligible MSM donors with the 1-year deferral in place. HIV rates were less than 0.6 per 100,000 donations and unchanged after each policy change (p = 0.14 for trend). Incidence remained unchanged at 0.22 per 100,000 person-years before implementation, 0.54 per 100,000 after 5-year deferral, and no incident cases after 1-year deferral (p = 0.55). CONCLUSION: Progressively shorter time deferrals had no impact on noncompliance of MSM with a male partner in the past year. Contrary to modeling predictions, shorter time deferrals had no impact on HIV rates or incidence. There was a modest increase in eligible MSM in the donor pool after each shorter time deferral. These results support the safety of reducing deferral periods for MSM.

Two-year follow-up of donors in a large national study of ferritin testing.

BACKGROUND: We assessed donor return rates, donation frequency, and factors related to the evolution of ferritin levels 2 years after entering donors into a large operational study of ferritin testing. STUDY DESIGN AND METHODS: Ferritin testing was done on donors from representative clinics (n = 12,595). Low-ferritin donors (<25 µg/L) were informed and not called for 6 months to book a donation. Approximately 37% of donors had ferritin retested on a return donation. Return rate and donation frequency were monitored, and a logistic regression model was constructed. RESULTS: The return rate was lower in low-ferritin donors (67% vs. 78%), particularly in women who were first-time donors (36% vs. 61%). Returning low-ferritin donors made fewer donations in the 2 years after notification compared to the 2 years prenotification (4.5 vs. 7.5 for men, 3.0 vs. 5.0 for women), while donation frequency was lower and increased slightly for normal-ferritin donors (4.7 vs. 4.4 for men, 3.6 vs. 3.1 for women). An increased number of donations, shorter interdonation intervals, female sex, and younger age are associated with low ferritin levels on initial and repeat testing. Some recovery of ferritin occurred, but most low-ferritin donors continued to have low or borderline levels on retesting. CONCLUSION: Informing donors of low ferritin results had a long-lasting impact on return rates and donation frequency, requiring recruitment efforts to maintain adequacy of supply. Increasing the interdonation interval leads to some improvement in ferritin levels; more sustained efforts to encourage donors to improve iron intake are needed to achieve long-term benefit.

Variant Creutzfeldt-Jakob disease deferral in Canada: impact of stop dates.

BACKGROUND: To reduce the risk of variant Creutzfeldt-Jakob disease (vCJD) transmission via blood transfusion in Canada, potential donors who spent a cumulative time in the United Kingdom, Western Europe or Saudi Arabia are deferred. "Stop dates" for accumulated time were later implemented for 3 months spent in the United Kingdom or France (1980-1996) and for 5 years elsewhere in Western Europe (1980-2007); Saudi Arabia deferral was implemented with the "stop date" (1980-1996). We evaluated the long-term impact of these deferrals and "stop dates", as well as the consistency of donors' answers to post-implementation screening questions. MATERIALS AND METHODS: The monthly deferral rate was monitored from 2003-2015. Time series methods (ARIMA) were used with interruption when "stop dates" were implemented. A telephone survey of 1,000 donors (250 first-time, 500 repeat deferred donors, 250 non-deferred control donors) assessed travel history (response rate 62%). An anonymous mail survey of 40,000 donors assessed compliance with deferral (response rate 45.3%). RESULTS: When the "stop date" for UK/France travel was implemented, the deferral rate decreased for first-time (2.1% to 1.1%, p<0.0001) and repeat (0.2% to 0.03%, p<0.0001) donors. The deferral rate increased after Saudi Arabia was included (mean increase of 0.4% first-time, 0.02% repeat, p<0.0001). After the Western Europe "stop date" the deferral rate was unchanged in first-time donors (1.0% to 1.1%, p=0.5) but decreased in repeat donors (0.03% to 0.02%, p<0.002). In the telephone survey, 94% of deferred donors confirmed deferrable travel history. In the anonymous survey 0.3% of donors were non-compliant with the UK/France deferral. DISCUSSION: Donors, particularly first-time ones, continue to be lost due to vCJD travel deferral, but most deferrals are correctly applied and non-compliance is rare. The application of a "stop date" reduced deferrals for UK/France travel, but it may be too early to see the full impact of the "stop date" for Western Europe.

A large national study of ferritin testing in Canadian blood donors.

BACKGROUND: We assessed risk groups for iron deficiency and the feasibility and efficacy of ferritin testing in a large blood center. STUDY DESIGN AND METHODS: Donors were informed of possible testing in the predonation pamphlet. Plasma ferritin was measured on retention samples (n = 12,595) from representative clinics. Low-ferritin donors (<25 µg/L) were sent a letter and information sheet and not called for 6 months. Ferritin testing was repeated on 25% of donors; donor return rate and frequency were monitored. RESULTS: Low-ferritin donors represented 2.9% of first-time and reactivated (no donation in past 12 months) male donors, 32.2% of first-time and reactivated female donors, 41.6% of repeat male donors, and 65.1% of repeat female donors. A mean of 11.7 months after index donation, the return rate was 76% for normal and 58% for low-ferritin donors; returning low-ferritin donors had made approximately one fewer donation. Ferritin increased by 16.3 and 12.1 µg/L in male and female low-ferritin donors and decreased by 17 µg/L in male and female normal-ferritin donors. CONCLUSION: The minimum hemoglobin level will be increased to 130 g/L for male donors and the minimum interdonation interval changed to 84 days (four donations yearly) for female donors based on iron deficiency risk groups. Large-scale ferritin testing was feasible. Donors informed of low-ferritin results had a lower return rate, donated less often, and had an increase in ferritin on return, approximately 1 year after initial testing, compared to donors with normal ferritin results.

Impact of a 5-year deferral from blood donation for men who have sex with men.

BACKGROUND: The deferral for men who have sex with men (MSM) changed from a permanent deferral since 1977 to a 5-year deferral on July 22, 2013, in Canada. We assessed the impact on safety and adequacy of the blood supply at Canadian Blood Services. STUDY DESIGN AND METHODS: Human immunodeficiency virus (HIV) rates were monitored from January 1, 2010, to July 21, 2015. Risk factors were assessed in notification interviews. Anonymous online surveys of male whole blood donors assessed compliance before and after implementation. RESULTS: HIV rates were 0.2, 0.5, and 0.51 per 100,000 donations in 2010 to 2012; they were 0.54 and 0.22 in the first and second years after implementation (p = 0.8). Of four male HIV-positive donors after implementation, three denied risk factors and one knew he had HIV. Before implementation 9669 of 19,437 (49.7%) donors participated in the survey, and after implementation, 6881 of 18,934 (36.3%). Before implementation 0.67% of male donors were noncompliant, and after implementation, 0.44%. There was no difference before versus after implementation in male donors with MSM history in the past 5 years (0.37% vs. 0.43%, p = 0.54). After implementation, eligible MSM donors increased (0.42% vs. 0.66%, p = 0.04), with approximately 500 more donors in 2014. CONCLUSION: Implementation of a 5-year deferral for MSM had no impact on HIV rates in 2 years of postimplementation monitoring. Donor compliance improved after implementation due to MSM donors who were previously ineligible becoming eligible. There was no change in the percentage of male donors with recent male partners but there was a modest increase in eligible MSM in the donor pool.

How do I interpret a p value?

A p-value is a number between 0 and 1 that is extremely useful in interpreting research results. Using comparison of the means of two samples as an example, a p-value <0.05 suggests that there is enough evidence to presume a real difference between groups from which the samples were drawn (that the "null hypothesis" can be rejected). We say that the difference between the means is statistically significant. However, it isn't iron clad proof and there is still a chance that there is really no difference. Furthermore, a statistically significant difference may not be clinically significant if it is not enough to appreciably affect patient outcomes. We describe the theory behind p-values and some common errors in interpretation.

Frequency and risk factors for donor reactions in an anonymous blood donor survey.

BACKGROUND: Adverse donor reactions can result in injury and decrease the likelihood of donor return. Reaction reports captured in the blood center's database provide an incomplete picture of reaction rates and risk factors. STUDY DESIGN AND METHODS: We performed an anonymous survey, mailed to 40,000 donors in 2008, including questions about symptoms, height, weight, sex, and donation status. Reaction rates were compared to those recorded in our database. Possible risk factors were assessed for various reactions. RESULTS: The response rate was 45.5%. A total of 32% of first-time and 14% of repeat donors reported having any adverse symptom, most frequently bruising (84.9 per 1000 donors) or feeling faint or weak (66.2 per 1000). Faint reactions were two to eight times higher than reported in our database, although direct comparison was difficult. Younger age, female sex, and first-time donation status were risk factors for systemic and arm symptoms. In females, low estimated blood volume (EBV) was a risk factor for systemic symptoms. Only 51% of donors who consulted an outside physician also called Canadian Blood Services. A total of 10% of first-time donors with reactions found adverse effects information inadequate. CONCLUSION: This study allowed us to collect more information about adverse reactions, including minor symptoms and delayed reactions. Based on our findings of the risk factors and frequency of adverse reactions, we are implementing more stringent EBV criteria for younger donors and providing more detailed information to donors about possible adverse effects and their management.