Iron deficiency among French whole-blood donors: first assessment and identification of predictive factors.

BACKGROUND: The objectives of this study are to estimate the prevalence of iron deficiency (ID) among French whole-blood (WB) donors to identify factors associated with ID and to generate decision trees. STUDY DESIGN AND METHODS: A prospective National multicentre study was performed on WB donors from March 11, to April 5th, 2019. Samples were selected randomly to perform serum ferritin. ID was defined as ferritin value under 26 ng/ml. All results were stratified by sex. Factors associated with ID were analysed using multivariate logistic regression model. CART algorithm was used for decision trees. RESULTS: Eleven thousand two hundred fifty eight WB donors were included. ID was more frequent in women (39·5%) than in men (18·0%). Among 7200 repeated donors, women below 50 yo had a higher risk (OR = 2·37; [1·97-2·85] IC95) than those above 50 yo. Factors associated with ID were: haemoglobin level under the threshold at donation n-1 except for women and n-2 donation; a low mean corpuscular haemoglobin at n-1 and n-2 donations; a shorter interval since n-1 donation and between n-1 and n-2 donations except for women; and women who had given three or four times in the last year. CART algorithm defined high risk of ID subgroups within three populations of donors, new female donors, repeated male donors and repeated female donors. In these identified subgroups, prevalence of ID was up to 72·1%. CONCLUSIONS: Our study showed the high prevalence of ID among French WB donors, identified well-known and new factors associated with ID and defined algorithms predicting ID in three populations.

Incidence of H1N1 2009 virus infection through the analysis of paired plasma specimens among blood donors, France.

BACKGROUND: Knowledge of the age-specific prevalence of seroprotection and incidence of seroconversion infection is necessary to complement clinical surveillance data and statistical models. It provides the basis for estimating the future impact of influenza A (H1N1pdm09) and implementing appropriate prevention and response strategies. METHODS: Using a cross-sectional design, two-stage stratified sampling and paired plasma samples, we estimated the age-specific prevalence of a protective level of H1N1pdm09 antibodies in the French adult population before and after the 2009/10 pandemic, and the proportion of those susceptible that seroconverted due to infection, from a single sample of 1,936 blood donors aged 20-70 years in mainland France in June 2010. Samples with a haemagglutination inhibition (HI) titre ≥1∶40 were considered seropositive, and seroconversion due to infection was defined as a 4-fold increase in titre in the absence of H1N1pdm09 vaccination or pre-pandemic seropositivity. RESULTS: Out of the 1,936 donors, 1,708 were included in the analysis. Seroprevalence before the pandemic was 6.7% (95% CI 5.0, 8.9) with no significant differences by age-group (p = 0.3). Seroprevalence afterwards was 23.0% (95% CI 17.7, 29.3) with 20-29 year olds having a higher level than older groups (p<0.001). Seroconversion due to infection was 12.2% (95% CI 6.9, 20.5). Younger age-group, vaccination against H1N1 and being seropositive before the pandemic were strongly associated with post-pandemic seropositivity. CONCLUSIONS: Before the 2009/2010 winter influenza season, only 6.7% of the French mainland population aged 20-70 had a level of antibodies usually considered protective. During the first pandemic wave, 12.2% of the population seroconverted due to infection and the seroprevalence after the wave rose to 23%, either due to prepandemic seropositivity, infection or vaccination. This relatively low latter figure contributed to an extension of target groups for influenza vaccination for the 2010/2011 season.