LAUSR

Dear Sir, In the report by Ainley et al. ‘Prevalence of maternal alloantibodies in a large teaching hospital and their impact on outcomes of fetuses/neonates’ (2017), we recognise the significance of the dataset presented by the authors. This will be of great use to many, particularly those investigating the use of intraoperative cell salvage in Obstetrics and the risk of alloimmunisation. We had previously undertaken a similar, albeit much smaller, data collection, which was not as thorough. Our alloimmunisation rates were approximately 0·4%. Of this, anti-D accounted for 22%, anti-c 9%, anti-K 15%, other Rh antibodies 42% and others (such as Fy, Jk, S) 30%. Some patients had multiple antibodies. Regarding the reasons of sensitisation, 39% were due to a previous pregnancy and 11% due to a transfusion. Of the remainder, there was insufficient history to confirm whether the antibodies formed were from transfusion or pregnancy. To determine the cause of sensitisation in these remaining cases, a review of the patient’s notes would be required something, which was not conducted at the time. As such, our dataset is not complete, and we therefore welcome the report by Ainley. Also in the same article, we note that they have reclassified anti-S into the same group (3) as non-clinically significant antibodies, such as anti-M, anti-N, anti-Kpa, anti-Lea and anti-Leb. However, we feel that anti-S should be taken more seriously because, despite being a relatively infrequent cause of haemolytic disease of the fetus and newborn (HDFN), it can be significant. Anti-S is predominately of immunoglobulin G (IgG) and can therefore cross the placenta and has been implicated in both haemolytic transfusion reactions (HTRs) and severe or even fatal HDFN.