Quality improvement review of O positive blood in emergency transfusion.

BACKGROUND: We recently introduced a policy to use O positive red cells in emergency transfusions for males >16 years of age and females >50 years of age. Here, we investigate changes in emergency transfusion practice and rates of red cell alloimmunization with the use of O positive blood for emergency transfusion. STUDY DESIGN AND METHODS: State-wide retrospective review of emergency transfusions between June 2020 and June 2021. The laboratory information system and patient medical records were used to collect demographic details, indications for transfusion, usage of O positive and O negative blood and rates of alloimmunization. RESULTS: There were 2354 red cell units transfused to 1013 patients (male = 59%, average age = 53 years) during the 12-month period. O positive units accounted for 46.9% (1103 units) of emergency transfusions. However, 726 (30.8%) O negative units were transfused to patients without a mandatory indication for O negative blood. Twenty-eight patients (2.9%) had a red cell alloantibody prior to transfusion including anti-E (n = 10), anti-D (n = 4), and anti-K (n = 4). One patient with prior anti-D had mild delayed hemolysis. There were 19 patients (4.3%, median follow-up 22 days) who developed a red cell alloantibody after emergency transfusion and include anti-E (n = 10), anti-D (n = 7), and anti-C (n = 5). DISCUSSION: The use of O positive blood for emergency transfusion has saved 1103 O negative red cell units with no detriment to patient outcome. There remains potential to optimize use of O positive blood in emergency transfusion and to understand red cell alloimmunization rates in a prospective fashion.

Clinical utility of ADAMTS-13 testing in suspected thrombotic microangiopathy: an audit of ADAMTS-13 activity assay requests in routine practice from a tertiary hospital.

AIMS: Differentiation between thrombotic thrombocytopenic purpura (TTP) and other microangiopathic haemolytic anaemia (MAHA) processes can be difficult. Since the documentation of ADAMTS-13 deficiency in TTP, several ADAMTS-13 activity assays have been developed for use in the diagnosis of TTP and/or other microangiopathic disorders. We reviewed the clinical utility of ADAMTS-13 activity testing in suspected TTP, as used in routine clinical practice in a tertiary referral hospital. METHODS: All requests for ADAMTS-13 activity levels performed at our institution after introduction of the assay were retrospectively audited with respect to clinical diagnosis and results. RESULTS: In total 57 individual patients were tested, of whom only 46% had a MAHA process. Severe ADAMTS-13 deficiency was present in five TTP patients and in one patient with fulminant hepatic failure. CONCLUSIONS: Our experience suggests that severely reduced levels are relatively specific for TTP, but may also occur in fulminant hepatic failure. Patients without MAHA may have reduced ADAMTS-13 activity and there is significant overlap in the range of ADAMTS-13 activity seen in non-TTP MAHA diagnoses. This supports the observation that outside the diagnosis and (possible) follow-up of suspected idiopathic TTP, the ADAMTS-13 activity assay has limited clinical utility. Further education about the role of ADAMTS-13 activity testing is needed.

Review of neonatal alloimmune thrombocytopenia.

Neonatal alloimmune thrombocytopenia (NAIT), with an incidence of one in 1000 live births, is the most common cause of severe thrombocytopenia and intra-cerebral haemorrhage in term neonates. NAIT results from trans-placental passage of maternal antibodies against a paternally derived fetal platelet alloantigen. Clinical presentation varies from unexpected thrombocytopenia on a blood film in a well newborn to intracranial haemorrhage (ICH). In contrast to haemolytic disease of the newborn, NAIT can present in a first pregnancy, and subsequent pregnancies are usually more severely affected. The role of antenatal screening for maternal alloantibodies instead of fetal blood sampling to identify at-risk fetuses remains uncertain, but there is a trend towards less invasive maternally directed treatment for at-risk pregnancies. Neonatal management is aimed at preventing or limiting thrombocytopenic bleeding with transfusion of antigen-matched platelets.

Alloimmune neonatal neutropenia: can we afford the consequences of a missed diagnosis?

The incidence of alloimmune neonatal neutropenia (ANN) is poorly defined. The reported incidence is less than or equal to 0.1%. This prospective study of unselected pregnancies found an incidence of 0.81% based on results of screening 247 'full term' cord blood samples. Alloimmune neonatal neutropenia occurred more frequently in this population than expected from published historical data. Advances in techniques for antineutrophil antibody screening may have contributed to the higher incidence found in this study. The frequency of ANN supports increased surveillance and confirmatory serological testing in infants with unexplained neutropenia.