Bacterial testing of platelets - has it prevented transfusion-transmitted bacterial infections in Australia?

BACKGROUND AND OBJECTIVES: Australia introduced bacterial contamination screening (BCS) for platelet components in April 2008. This study presents analysis performed to assess the efficacy of testing. MATERIALS AND METHODS: Seven-day aerobic and anaerobic culture is performed using the BacT/ALERT 3D system. Following an initial machine positive (IMP) flag, all associated components are recalled, and/or clinicians treating already transfused patients are notified. IMPs are categorized as 'machine false positive', 'confirmed positive' or 'indeterminate' depending on culture results of initial and repeat samples. RESULTS: Between 2010 and 2012, 1·1% of platelet donations tested IMP; since 2013, this rate has fallen to 0·6% through improved instrument management, reducing false-positive IMPs but maintaining sensitivity for cultures yielding bacterial growth. On average, 66% of confirmed positive and indeterminate platelet units had been transfused at the time of detection. The majority (95%) of these grew Propionibacterium sp., a slow-growing organism that rarely causes sepsis in the transfusion setting. The incidence of reported transfuion-transmitted bacterial infection (TTBI) has fallen since the introduction of BCS, with a 4·2-fold [0·5, 28·2] lower rate from platelets. CONCLUSION: BCS has been successful in detecting platelet units containing pathogenic bacteria. The incidence of TTBI from platelets has fallen since the introduction of BCS, but the risk has not been eliminated due to rare false-negative results. In the absence of a pathogen inactivation system for red blood cells, BCS provides 'surrogate' testing of red blood cells from which platelets have been manufactured.

Understanding the effects of gamma-irradiation on potassium levels in red cell concentrates stored in SAG-M for neonatal red cell transfusion.

BACKGROUND AND OBJECTIVES: Red cell transfusions, to paediatric patients, are often gamma-irradiated to prevent transfusion-associated graft-versus-host disease. This study measured changes in potassium and other in vitro parameters immediately following gamma-irradiation of paediatric and full-size red cell concentrates (RCCs). MATERIALS AND METHODS: The effects of irradiation on potassium release in RCCs stored in SAG-M were investigated under three scenarios. In the first scenario, RCC < 5 days was split into paediatric packs, gamma-irradiated and tested for potassium and haemolysis at 0, 2, 4, 6, 24 and 48 h. In the second scenario, full-size RCCs < 5 days postcollection were gamma-irradiated and tested as for the paediatric packs. Thirdly, RCCs < 14 days postcollection were gamma-irradiated and assessed at 6 and 24 h and 7 and 14 days. Each group contained paired controls that were not gamma-irradiated. RESULTS: In all situations, gamma-irradiation resulted in a twofold increase in potassium concentrations after 24 h of storage, compared to matched unirradiated controls. This difference was detectable as early as 2 h postirradiation. Few differences were observed between control and irradiated RCCs in other key parameters, including ATP, 2,3-DPG, haemoglobin, pH, glucose and lactate concentration. CONCLUSION: Gamma-irradiation of RCCs significantly increased extracellular potassium. Irradiation of fresher RCCs results in lower potassium concentrations, which is less likely to lead to hyperkalaemia upon transfusion.

Surveillance for Ross River virus infection using blood donors.

The number of clinical Ross River virus (RRV) infections (epidemic polyarthritis) each year in Australia continues to grow despite extensive vector control programs. There is a need, therefore, for a surveillance program that can give sufficient warning of outbreaks of the disease so that highly focused preventative measures may be undertaken. The ability of a surveillance program, based on voluntary Red Cross blood donations, to predict outbreaks of epidemic polyarthritis was evaluated. Anti-RRV IgM antibody was detected in significant numbers of blood donors from throughout the state of Queensland 6-9 weeks prior to an increase in the number of notified cases of epidemic polyarthritis. At a local level, significant numbers of anti-RRV IgM blood donors were detected in Brisbane in 1996 four weeks prior to an increase in the number of notified cases of epidemic polyarthritis. This system of surveillance is technically simple, rapid (results are obtained in 2-3 days), it samples the human population from throughout the state, and it gives timely warning of outbreaks of epidemic polyarthritis.

Breast feeding in neonatal alloimmune thrombocytopenia.

Infants with neonatal alloimmune thrombocytopenia are at risk of severe intracranial haemorrhage. Placental transfer of maternal immunoglobulin G (IgG) directed against fetal platelet antigens is known to be the underlying mechanism. Since breast milk contains IgG it is theoretically possible that breast feeding of these infants could cause thrombocytopenia. The following case report shows that an infant with neonatal alloimmune thrombocytopenia may be safely breast fed, even when the breast milk contains the platelet specific antibody (HPA-1a).

The thrombin receptor.

1. The thrombin receptor has now been cloned and found to be a member of the G-protein-coupled seven-transmembrane domain receptor family. 2. The receptor has been detected directly in platelets, endothelial cells and smooth muscle cells and studies using receptor-derived peptides have demonstrated that this receptor may be the one responsible for many of the actions of thrombin in platelets, endothelial cells, smooth muscle cells, fibroblasts, mesangial cells and neural cells. 3. The receptor appears to be activated by the novel mechanism of cleavage by thrombin to yield a new N-terminus which then interacts with the receptor as a tethered ligand to initiate cell activation.

Neonatal alloimmune thrombocytopenia. A case report and a review of the literature.

A 32-year-old woman in her third pregnancy underwent fetal blood sampling because of a previous child with neonatal thrombocytopenia. At 33 weeks' gestation, fetal thrombocytopenia was diagnosed. Treatment was instituted antenatally with serial fetal platelet transfusions and corticosteroid therapy. Delivery was by Caesarean section at 37 weeks' gestation. Neonatal treatment included further platelet transfusion and immunoglobulin infusion. Recovery of the neonate was complete on discharge from hospital 10 days after birth. The aetiology, diagnosis, clinical presentations and therapeutic options in cases of alloimmune thrombocytopenia are discussed.