The selection and preparation of red cell components for intrauterine transfusion: A national survey.

BACKGROUND AND OBJECTIVES: The practice regarding the selection and preparation of red blood cells (RBCs) for intrauterine transfusion (IUT) is variable reflecting historical practice and expert opinion rather than evidence-based recommendations. The aim of this survey was to assess Canadian hospital blood bank practice with respect to red cell IUT. MATERIALS AND METHODS: A survey was sent to nine hospital laboratories known to perform red cell IUT. Questions regarding component selection, processing, foetal pre-transfusion testing, transfusion administration, documentation and traceability were assessed. RESULTS: The median annual number of IUTs performed in Canada was 109 (interquartile range, 103-118). RBC selection criteria included allogeneic, Cytomegalovirus seronegative, irradiated, fresh units with most sites preferentially providing HbS negative, group O, RhD negative, Kell negative and units lacking the corresponding maternal antibody without extended matching to the maternal phenotype. Red cell processing varied with respect to target haematocrit, use of saline reconstitution (n = 4), use of an automated procedure for red cell concentration (n = 1) and incorporation of a wash step (n = 2). Foetal pre-transfusion testing uniformly included haemoglobin measurement, but additional serologic testing varied. A variety of strategies were used to link the IUT event to the neonate post-delivery, including the creation of a unique foetal blood bank identifier at three sites. CONCLUSION: This survey reviews current practice and highlights the need for standardized national guidelines regarding the selection and preparation of RBCs for IUT. This study has prompted a re-examination of priorities for RBC selection for IUT and highlighted strategies for transfusion traceability in this unique setting.

Preparing small-dose red cell concentrates (RCCs) for neonatal and pediatric transfusions: Impact of RCC volume, storage, and irradiation.

BACKGROUND: Preparing small-dose red cell concentrates (RCCs) is a common practice for pediatric and neonatal transfusions. However, there is a lack of quality monitoring data to indicate that both the preparation and storage of small-dose RCCs does not alter in vitro red cell quality. The present study seeks to provide data to support this practice. MATERIALS AND METHODS: To evaluate quality of stored small aliquots, six ABO/Rh matched leukoreduced citrate phosphate-dextrose/saline-adenine-glucose-mannitol (LR CPD/SAGM) RCCs were pooled and split into 30 ml aliquots, 80 ml aliquots, and a standard 290 ml unit, with testing performed for up to 43 days post-collection. To evaluate the impact of irradiation on small-dose RCC preparation, a total of 48 independent LR CPD/SAGM RCCs were used (non-irradiated: n = 24; irradiated: n = 24). Aliquoting with/without irradiation was performed within 7 days of collection and baseline testing was performed within 24 h of aliquot production. RESULTS: Limited variability in hemolysis, mean cell volume, and extracellular potassium concentrations were seen between the different aliquot sizes throughout the 43-day storage period. Aliquot production did not accentuate damage based on any of these tested parameters in both the non-irradiated and irradiated subsets. A significant increase was seen in the potassium concentrations in the irradiated parent and aliquot samples relative to their non-irradiated counterparts. CONCLUSIONS: Non-irradiated small-aliquot dose RCCs meet in vitro quality criteria required for safe transfusion throughout the 42-day storage period. The same can be said for aliquots derived from irradiated units and tested within 24 h of aliquot production.

Babesia microti in a Canadian blood donor and lookback in a red blood cell recipient.

BACKGROUND AND OBJECTIVES: We describe the third documented case of autochthonous human babesiosis in Canada and the second in a Canadian blood donor. MATERIALS AND METHODS: Multiple laboratory investigations were carried out on the donor and the immunocompromised recipient of an associated, potentially infectious red blood cell product. RESULTS: The donor had not travelled except for outdoor exposure in south-eastern Manitoba, followed by illness and hospital admission. The donor had a notable parasitaemia, positive for Babesia microti using whole blood nucleic acid testing (NAT). The recipient was negative for B. microti by both serology and NAT. CONCLUSION: There was no evidence of transfusion-transmitted babesiosis.

Electronic patient identification for sample labeling reduces wrong blood in tube errors.

BACKGROUND: Wrong blood in tube (WBIT) errors are a preventable cause of ABO-mismatched RBC transfusions. Electronic patient identification systems (e.g., scanning a patient's wristband barcode before pretransfusion sample collection) are thought to reduce WBIT errors, but the effectiveness of these systems is unclear. STUDY DESIGN AND METHODS: Part 1: Using retrospective data, we compared pretransfusion sample WBIT rates at hospitals using manual patient identification (n = 16 sites; >1.6 million samples) with WBIT rates at hospitals using electronic patient identification for some or all sample collections (n = 4 sites; >0.5 million samples). Also, we compared WBIT rates after implementation of electronic patient identification with preimplementation WBIT rates. Causes and frequencies of WBIT errors were evaluated at each site. Part 2: Transfusion service laboratories (n = 18) prospectively typed mislabeled (rejected) samples (n = 2844) to determine WBIT rates among samples with minor labeling errors. RESULTS: Part 1: The overall unadjusted WBIT rate at sites using manual patient identification was 1:10,110 versus 1:35,806 for sites using electronic identification (p < 0.0001). Correcting for repeat samples and silent WBIT errors yielded overall adjusted WBIT rates of 1:3046 for sites using manual identification and 1:14,606 for sites using electronic identification (p < 0.0001), with wide variation among individual sites. Part 2: The unadjusted WBIT rate among mislabeled (rejected) samples was 1:71 (adjusted WBIT rate, 1:28). CONCLUSION: In this study, using electronic patient identification at the time of pretransfusion sample collection was associated with approximately fivefold fewer WBIT errors compared with using manual patient identification. WBIT rates were high among mislabeled (rejected) samples, confirming that rejecting samples with even minor labeling errors helps mitigate the risk of ABO-incompatible transfusions.

Resolving variable maternal D typing using serology and genotyping in selected prenatal patients.

BACKGROUND: RhIG prophylaxis for D- pregnant women prevents hemolytic disease of the newborn and typically depends on results of serologic D typing. Interpretation and follow-up of weak D serology is variable. Recent recommendations promote genotyping for RHD status determination in those with weak D serology. Canadian Blood Services performs comprehensive serologic prenatal testing in four provinces. Genotyping is used to determine D typing in patients with weak D. STUDY DESIGN AND METHODS: A serologic algorithm identified which patients require genotyping for RHD determination. Genotyping was performed on one of two commercially available platforms. RESULTS: Only 0.4% of D- patients met criteria for genotyping. Sixty-one percent were weak D Type 1, 2, or 3. Thirty percent had a partial or weak D other than Type 1, 2, or 3. Eleven had variants which remained unresolved. Seventeen were D+ and four were D-. CONCLUSIONS: Genotyping of patients with weak D serology led to an identified genotype in most patients. RhIG administration was avoided in 66% who were weak D Type 1, 2, or 3 or were D+. The use of a serologic algorithm to select patients for RHD genotyping identifies a majority of patients with weak D types not at risk for alloimmunization. This approach limits the number of genotyping investigations and the cost of providing classification for weak D types.

The prevalence of anti-K in Canadian prenatal patients.

BACKGROUND: Anti-KEL1(K) is a major cause of hemolytic disease of the fetus and newborn. We utilized data from prenatal testing of patients in Western Canada to determine the frequency of anti-K. In Manitoba, we evaluated the frequency of transfusion as the likely cause for alloimmunization. We reviewed international practices to prevent alloimmunization. STUDY DESIGN AND METHODS: Prenatal patients undergo antibody screening using an automated testing platform and uniform testing algorithm. Data on the frequency of antibodies, transfusion history, and donor K typing were extracted from the relevant databases at Canadian Blood Services. National standards were reviewed with the help of local experts. RESULTS: Anti-K was found in 397 of 390,193 patients from 2011 to 2013 (1.02 per 1000) and was the second most frequent antibody after anti-E. In Manitoba, 26 of 75 (35%) anti-K patients had received transfusions in the province since 2001; 14 of the 26 (54%) had received at least one K+ RBC unit and three had received all K- units, while in nine, donor K typing was incomplete. Only eight of the 26 had previous pregnancies, three with K+ partners. International practice varies; however, prophylactic use of matched or K- units is standard in many European countries. CONCLUSIONS: Anti-K was found in 0.1% of prenatal patients. Although our data on the history of transfusion are incomplete, they demonstrate that transfusion with a K+ unit is a major cause of alloimmunization. Given advances in phenotyping and genotyping technologies, prophylactic matching should be considered in Canada.

Weak D type 67 in four related Canadian blood donors.

Correct donor D typing is critical to prevent recipient alloimmunization. No method can detect all variants, and the immunogenicity of many variants is unknown. Routine ABO and D serologic typings are performed in our laboratory by automated microplate testing. Until 2011, routine confirmation of D- status of first-time donors was performed by the manual tube indirect antiglobulin test (IAT); this was replaced by automated solid-phase testing including weak D testing by IAT. Selected donors are investigated by other methods. We describe four weak D type 67 (RHD*01W.67) donors whose samples tested as D- by automated microplate and manual methods but were later determined to be D+ by automated solid-phase and RHD gene analysis. Solid-phase serologic and molecular typing results of all four donors were identical. It was identified that the donors are of English-Irish descent; two are brothers and the others are cousins. Transfusion of blood from one of these donors likely resulted in alloimmunization to D in one of three recipients tested since no other documented exposures were identified. Lookback studies determined that two other D- recipients were not alloimmunized.

West Nile virus in Canadian blood donors.

BACKGROUND: Blood donation screening for West Nile virus (WNV) RNA by nucleic acid testing (NAT) was implemented in Canada in July 2003, and 14 WNV RNA-positive donations were identified. Samples were screened in minipools of six donations with a WNV assay (TaqScreen, Roche). Two of the donors were identified by single-donor screening that was initiated in the province of Saskatchewan, which had the highest prevalence of WNV in the country, in early September 2003. STUDY DESIGN AND METHODS: The original 14 samples and follow-up samples (2-35 days after donation), available from 13 of the 14 donors were tested with an in-house, real-time, quantitative WNV NAT assay that was specific for WNV. A Health Canada reference reagent was used for calibration. Immunoglobulin M (IgM) and immunoglobulin G (IgG) levels were determined with commercial enzyme-linked immunosorbent assay kits. RESULTS: All donors tested positive for the presence of WNV with the in-house assay. Two donors, 18 and 19, identified by single-donor testing, had extremely low levels of viremia and that could only be detected in 1:38 or 1:39 replicate tests. The titers of the remaining index samples ranged from below log2.8 (the limit of quantitation) to log4.7 NAT detectable units per mL. Three samples, from Donors 17, 18, and 19, were IgM-positive, whereas samples from Donors 18 and 19 were also IgG-positive. The remaining 10 donors with follow-up samples all seroconverted. CONCLUSION: The 14 WNV donor samples detected by routine screening were confirmed as WNV RNA-positive by a WNV RNA-specific in-house assay and by demonstration of seroconversion in 13 of the 14 donors.