Lessons from the response to the threat of transfusion-transmitted vCJD in Ireland.

By the time vCJD was first described in 1996, it was already far too late to offset further disaster from transmission of the disease by blood transfusion: almost all the humans who would be infected and infectious were already diseased. Nothing done by the blood transfusion services around that time, with the exception of excluding transfusion recipients as blood donors, would have made any useful contribution to containing the extent of the epidemic. The ability to spread emerging diseases before the problem is manifest or understood is a fixed and unavoidable feature of blood transfusion as it is practiced today. A second fixed property of blood transfusion is that the root cause of disaster is not within the control of the blood transfusion universe. Strategies that have emerged to cope with similar threat in other enterprises that also contain these properties comprise the components of robust design: surveillance, preparedness for action, engagement, herding together, evasion or avoidance, early adoption of potentially useful measures, engineered resilience, defence in depth, damage limitation including modularity and removal of feedback loops, and contingency, redundancy and failure management, and ultimately, individual escape. Early adoption of leucodepletion based on the possibility that it might work rather than any hard evidence was a good example of threat management. Exclusion of previously transfused donors is a robust mechanism for containing any future infection; optimal blood use structures that provide a national transfusion rate as low as possible also constitute an effective threat management strategy.

Pathogen reduction: state of reflection in Ireland.

The Irish Blood Transfusion Service is currently assessing the feasibility and affordability of implementing pathogen reduction for platelets in Ireland. Since 2002, almost all plasma transfused in the country has been subjected to a pathogen reduction process in the form of Octaplas™ (or Uniplas™ for group AB recipients), manufactured from plasma from donors at the South Texas Blood and Tissue Center, San Antonio, TX, USA. Pathogen reduction of platelets for Ireland is driven by two major concerns: by the need for robust systems to prevent the transmission of any emerging transfusion transmissible infections or of diseases for which we do not currently test, and by the poor sensitivity and efficacy of even the most sensitive available approaches to bacterial contamination of platelets. While the safety of blood transfusion is a matter of public safety rather than health economics, it is currently the case that money spent in Ireland on pathogen reduction of platelets will result in fewer resources available for public use elsewhere, so that detailed cost balancing is required in deciding whether or not to implement pathogen reduction. Considerations that influence the costs of implementation in our hands include the ability to discontinue platelet irradiation, the ability to maintain a single inventory from the point of view of CMV, extending storage to day 7 of shelf-life as a routine, and avoidance of travel deferrals for platelet donors.

Phase I/II safety study of transfusion of prion-filtered red cell concentrates in transfusion-dependent patients.

BACKGROUND AND OBJECTIVES: Variant Creutzfeldt-Jakob (vCJD) is a fatal transfusion transmissible prion infection. No test for vCJD in the donor population is currently available. Therefore, prion removal by filtration of red cell concentrate (RCC) is an attractive option for prevention. MATERIALS AND METHODS: Twenty patients were recruited with ethical permission, to receive clinically necessary transfusion containing one unit of pfRCC. Follow-up at 24 hours, 6 weeks and 6 months was undertaken. A second pfRCC was administered to 6 patients with similar follow up. pfRCC were prepared using the CE marked P-Capt device by the IBTS. RESULTS: In 20 transfused patients undergoing one exposure to a prion filtered unit, no attributable adverse events were noted. A subset of these (n = 6) underwent re-exposure to a further filtered unit without incident. CONCLUSIONS: This phase 1/11 clinical study provides encouraging data on safety of prion filtration which can be used to plan more extensive studies on the use of filtered blood in adults and children.

Capillary and venous haemoglobin levels in blood donors: a 42-month study of 36,258 paired samples.

BACKGROUND: EU law requires a haemoglobin of > or = 12.5 g/dl for women or > or = 13.5 g/dl for men at the time of donation. As capillary and venous haemoglobin values may differ in the same subject, we examined whether a capillary haemoglobin level of 12.0 g/dl for women or 13.0 g/dl for men, is equivalent to a venous haemoglobin level of > or = 12.5 g/dl and > or = 13.5 g/dl, respectively, to avoid unnecessary loss of blood donations. METHODS: Over a continuous 42-month period, 36 258 paired capillary and venous samples were taken from 25 762 females and 10 496 males, when the capillary haemoglobin was < 12.5 g/dl and < 13.5 g/dl respectively. RESULTS: Venous haemoglobin levels were higher than capillary levels, with a mean difference of 1.07 g/dl (SD 0.68 g/dl), range -2.2 to +3.25 g/dl for men (P < 0.001), and a mean difference of 0.67 g/dl (SD 0.65 g/dl), range -2.5 to +5.4 g/dl for women (P < 0.001). The difference for the three consecutive winters was 0.78 g/dl (SD 0.081 g/dl) for females and 1.26 g/dl (SD 0.162 g/dl) for males and for the three consecutive summers was 0.56 g/dl (SD 0.089 g/dl) for females and 0.88 g/dl (SD 0.134 g/dl) for males: P < 0.001. CONCLUSIONS: Capillary haemoglobin levels of 12.0-12.5 g/dl in healthy females or 13.0-13.5 g/dl in healthy males are substantively equivalent to venous haemoglobin levels of > or = 12.5 and > or = 13.5 g/dl for women and men respectively. This finding has permitted an additional 32 990 blood units to be collected over the period of the study, a gain of 9.4%.

In vitro assessment of red-cell concentrates in SAG-M filtered through the MacoPharma P-CAPT prion-reduction filter.

This study investigated whether filtration of leucodepleted red cells in SAG-M through the P-CAPT filter in order to prevent the potential risk of vCJD infection associated with prion transmission through transfusion has any deleterious effect on red-cell quality. Bottom-and-top SAG-M leucodepleted red-cell concentrates (24 units) were prion-reduction filtered on the day following collection, with half of the units undergoing irradiation on day 14. A control group (12 units) was not prion filtered. Units were sampled at 7-day intervals up to day 35 and tested using standard measures of red-cell quality as well as prothrombin content (to examine prion filter efficacy). Haemoglobin loss per unit was approximately 9 g and in some cases levels were below standard specification (40 g). Haemolysis increased significantly after filtration [0.01 (0.00-0.05) vs. 0.23 (0.07-0.52, p<0.001)]. Prothrombin levels were reduced 41.6-fold compared to leucodepleted red-cell units. Product specifications were within or close to routine acceptable levels. Owing to the reduction in haemoglobin levels below those specified, it may be preferable to reduce haemoglobin specification levels and transfuse more prion-filtered units rather than transfuse potentially unsafe blood product. The risk of transfusing more units with less haemoglobin should be offset against the risk of transfusing unfiltered blood.

Screening platelet concentrates for bacterial contamination: low numbers of bacteria and slow growth in contaminated units mandate an alternative approach to product safety.

BACKGROUND AND OBJECTIVES: We introduced 100% screening of platelets for bacterial contamination in 2005 to reduce the risk of clinical sepsis from platelet transfusion. We test all outdating units again at expiry to assess the sensitivity of the initial test. MATERIALS AND METHODS: We test all platelet concentrates prior to release for clinical use using a large volume automated culture technique on the day after manufacture. All units that expire unused are retested. Platelets still in stock on day 4 of storage may have a repeat culture performed, and are returned to stock with two extra days of shelf life. RESULTS: Of 43,230 platelet units screened, 35 (0.08%) were positive; of 8282 expired unused, 18 (0.22%) were positive; and of 3310 day-4 retests, four (0.12%) were positive. Overall sensitivity of the initial screening test was 29.2% (95% confidence interval 19.4 to 39.1%). Thirteen of the 35 positive screening tests would have been expected to grow in both aerobic and anaerobic bottles; eight grew in aerobic culture only and five grew in anaerobic culture only, indicating that the likely number of bacteria in the contaminated platelet units at the time of sampling was less than 60 colony-forming unit per platelet unit. CONCLUSIONS: Screening platelet concentrates for bacterial contamination using the most sensitive method available has a sensitivity of less than 40% because of the low numbers of bacteria in the initial contamination. Effective resolution of this problem will require a pathogen-inactivation technique.

Solvent-detergent plasma: use in neonatal patients, in adult and paediatric patients with liver disease and in obstetric and gynaecological emergencies.

The study was conducted to assess the efficacy and tolerance of solvent-detergent (SD) plasma in neonates, in obstetric and gynaecological patients and in patients with liver disease in three large hospitals in Dublin during the period 1 April 2002 (when SD plasma was introduced) through 31 October 2003. Forty-one neonates received 67 transfusions of SD plasma at a mean dose +/- standard deviation of 18.4 +/- 13.2 mL kg(-1). Thirty-one (75.6%) patients had coagulopathy without haemorrhage (either disseminated intravascular coagulopathy or other coagulopathy); a further eight (19.5%) had clinical haemorrhage (excluding intraventricular haemorrhage), which complicated a coagulopathy. Thirty-eight obstetric and gynaecological patients received 57 SD plasma transfusions at a mean dose of 15.3 +/- 7.7 mL kg(-1). Thirty-six women (94.7%) had haemorrhage with mean blood loss per patient of 3345.8 +/- 2738.1 mL. Fifteen children with liver disease received 33 SD plasma transfusions at a mean volume of 38.0 +/- 41.5 mL kg(-1) body weight. Seventeen adult patients with severe end-stage liver disease were transfused with SD plasma either following liver transplantation or prior to other invasive procedures, at a mean dose of 10.2 +/- 3.4 mL kg(-1). There were statistically significant decreases in mean activated partial thromboplastin time and prothrombin time in neonates, in obstetric and gynaecological patients and in patients with liver disease. Complete correction of coagulation parameters was not achieved in any case in the liver transplant group. No adverse reactions were observed for SD plasma infusion. Use of SD plasma in critically ill neonates, in women with obstetric and gynaecological emergencies and in patients with liver disease appears safe, and improves laboratory indices of coagulopathy.

Neonatal alloimmune thrombocytopenia in the Irish population: a discrepancy between observed and expected cases.

AIMS: To estimate the rate of detection of neonatal alloimmune thrombocytopenia (NAITP) in the Irish population, to investigate clinical presentation and outcome in affected infants, and to determine the extent, if any, to which this condition is underdiagnosed at present. METHODS: Cases were collected in a retrospective fashion from a review of platelet serology laboratory records from January 1992 to December 2000. Clinical data were obtained from hospital records. Testing for maternal antiplatelet antibody was by one or more of the following: the platelet suspension immunofluorescence test, a commercial antigen capture enzyme linked immunosorbent assay (GTI-PakPlus), and the monoclonal antibody immobilisation of platelet antigens assay. Platelet antigen typing was by the polymerase chain reaction technique with sequence specific primers. RESULTS: Twenty seven serologically verified cases of NAITP were identified in 18 families. Maternal antibody to human platelet antigen 1a accounted for 25 of the 27 confirmed cases. Twenty one of 26 infants were born with severe thrombocytopenia. Nineteen of 27 infants had bleeding manifestations at birth. Petechiae and bruising were most commonly observed (n = 17). There were no documented cases of intracranial haemorrhage in this group but systematic cranial ultrasound was not performed. CONCLUSIONS: Screening studies in predominantly white populations have estimated the incidence of NAITP to be between 1 in 1000 and 1 in 2000 live births. With 50 000 births each year in Ireland, these results give a clinical detection rate for NAITP of just 1 case in 16 500 live births, strongly suggesting that NAITP is currently underdiagnosed. Antenatal screening to detect women at risk of having babies with NAITP is now scientifically feasible and should be considered.

Haemolytic uraemic syndrome: prognostic factors.

Haemolytic uraemic syndrome (HUS) associated with Escherichia coli O157:H7 is the commonest cause of acute renal failure (ARF) in childhood. Production of verotoxin by the organism is pivotal in the pathogenesis of the disease. Verotoxin binds to a receptor on blood and endothelial cells, expressed as the P1 blood group antigen on red blood cells. A protective effect of the P1 phenotype has been proposed in this disease. This study investigates prognostic factors and the relationship between outcome and P1 phenotype in 27 cases of diarrhoea-associated HUS. A poor outcome as defined by the presence of chronic renal failure (CRF), hypertension or proteinuria on 6 month follow-up was associated with the age of the patient at presentation and with the following clinical markers: maximum WBC and duration of raised WBC, duration of anuria and duration of need for dialysis. None of these outcome measures or prognostic factors, and no extra-renal manifestations of the disease were associated with P1 phenotype.

Coagulase-negative staphylococcal contamination of whole blood and its components: the effects of WBC reduction.

BACKGROUND: Most bacteria present in blood components are normal skin flora, particularly Staphylococcus epidermidis and other coagulase-negative staphylococci. Growth patterns of these bacteria and the effects of different methods of component preparation may depend on variations in behavior between different isolates of the same species. STUDY DESIGN AND METHODS: Whole-blood units were inoculated with 19 different coagulase-negative staphylococcus (CNS) isolates at 1 to 10 and 10 to 100 CFUs per mL. After overnight holding at 22 degrees C, the units were processed into components. The components were cultured before inoculation and during processing, including before and after WBC reduction. RESULTS: At low inoculum levels, CNS was detected in 15 (79%) of 19 whole-blood units and in 12 (63%) of 19 RBCs after separation; after filtration, bacteria were detected in 3 (16%) of 19 (p = 0.0069). For platelet concentrates, 6 (32%) of 19 grew bacteria before filtration and 1 of 18 after filtration (difference not statistically significant). Three (16%) of 19 plasmas were positive before and after freezing. At high inoculum levels, 16 (89%) of 18 whole-blood samples and RBCs were positive before filtration; 6 (33%) of 18 RBCs were positive after filtration (p = 0.0002); 8 (44%) of 18 platelets were positive before filtration; 3 (17%) of 18 were positive after filtration (difference not statistically significant), and 7 (37%) of 18 plasma samples were positive before and after freezing. CONCLUSION: The growth characteristics of CNS in blood components vary with differences either in the subtype of bacteria or in the donor blood. Filtration reduces but does not eradicate contamination of RBCs and platelets by CNS. Plasma may act as a reservoir for CNS infection.

Effects of asymptomatic abdominal aortic aneurysm on the soluble coagulation system, platelet count and platelet activation.

OBJECTIVES: the aim of the study was to determine the effects of infrarenal asymptomatic abdominal aortic aneurysm (AAA) on platelet count and activation. DESIGN: prospective clinical study in a University Department of Vascular Surgery. PATIENTS: one hundred and five patients with AAA. Thirty-two control patients with symptomatic carotid artery stenoses. METHODS: platelet count (PC), plasma glycocalicin levels, prothrombin ratio (PTR), activated partial thromboplastin time (APPT), fibrinogen and D-dimer were measured in 23 patients with AAA and 16 control patients with symptomatic carotid artery stenoses. PC alone was measured in a further 84 patients with AAA and 16 with carotid artery stenoses. RESULTS: PC was below the normal range in 8/105 patients and mean PC (215x10(9)/l, S.D. 47.5) was significantly lower than that of a control population (242x10(9)/l, S.D. 16.8) and patients with carotid disease (269x10(9)/l, S.D. 57). Glycocalicin level was above the normal range in 7/23 patients and the median level (28 fg/plt) was significantly higher than that of a normal population (21.6 fg/plt) and patients with carotid disease (12.3 fg/plt). Fibrinogen levels, PTR and APPT were all within the normal range. One patient had a minimally elevated level of D-dimer. CONCLUSIONS: the combination of low PC and high glycocalicin levels suggests that there is increased platelet destruction, most likely due to activation within the aneurysm sac.

Developmental variation in stem-cell markers from human fetal liver and umbilical cord blood leukocytes.

Fetal tissues containing haematopoietic stem cells (HSC) are of potential value for allogeneic transplantation and gene therapy. Flow cytometry was used to investigate CD34+ cells from human fetal livers and umbilical cord (placental) blood (UCB). CD34+ cells, expressed as a proportion of CD45-positive leukocytes, were much more abundant in fetal livers (mean 38%) than in UCB (mean 0.3%), but fetal liver cells had lower proportions of CD34+HLA-DR+ and CD34+ CD38+ subsets. In fetal liver, there was a strong and highly significant inverse correlation between CD34+ cells (as a proportion of total leukocytes) and gestational age; no such relationship was found for subsets of CD34+ cells coexpressing CD38 or CDw90 (Thy-1), but CD34+HLA-DR+ cells were less abundant in first-compared to second-trimester livers. In UCB, a trend towards decreasing CD34+ cells (as a proportion of total leukocytes) with increasing gestational age in late pregnancy was also observed. The composition of fetal leukocytes changes during development, and therefore the timing of fetal HSC harvesting could be of relevance to transplantation outcome.