Case 103 – summary

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Our patient has an intravascular transfusion reaction which was likely due anti C with undetectable antibodies. Red cell phenotyping of the patient and the transfused red cells help identify the likely antibody. Red cell survival studies offered reassurance in this patient, although not widely used for this purpose. This is an unusual case, but aims to demonstrate the presentation of an intravascular haemolytic transfusion reaction and the process of investigating difficult to identify antibodies.

Following the red cell survival studies our patient went on to have transfusions with C negative red cells with no reactions. Creatinine returned to baseline and she was discharged. She went on to complete her adjuvant chemotherapy with some red cell support. Our patient was provided with an antibody card to make people aware if she has future transfusions.

In this summary we will discuss more generally about transfusion reactions, and then about haemolytic reactions, and the possible reasons for the unidentifiable antibody in this case.

Acute transfusion reactions are a relatively common complication of transfusion. The causes of reactions eg haemolytic, bacterial contamination, TACO, TRALI can often present with similar symptoms and the same steps should be put in place for every transfusion in order to minimise the risk of reactions, and to enable early identification and appropriate management of a patient when a reaction does occur.

Processes are put in place before the blood even reaches the patient to ensure safer transfusion, such as donor questionnaire, testing of the donation for various infections and leucodepletion.

Appropriate patient blood management tries to ensure that patients only get necessary transfusions.

Once it has been decided a patient needs a transfusion this needs to be done in an appropriate place with staff trained in transfusion and complications arising from it.

Complications from transfusions do not always happen during the transfusion, so it is important to advise patients to seek medical advice if they become unwell within 24 hours of the transfusion (although complications such as delayed haemolytic transfusion reaction can present several days later).

If the patient becomes unwell during the transfusion, it should be stopped and the patient assessed. It is important to ensure the unit and the patient details are checked to ensure correct blood component and correct patient. The unit should also be inspected to see if there is an unusual appearance/clumps that may suggest bacterial contamination.

Patients should receive medical attention and be treated symptomatically with assessment of A,B,C. Further details of management of reactions can be found in the BSH guidelines on acute transfusion reactions listed at the end of this summary.

Laboratory investigations

If transfusion reaction is suspected the basic tests that should be performed are

FBC

DAT

LDH

Haptoglobins

LFT

U&E

Urine for haemoglobinuria if concern regarding HTR

Repeat samples for compatibility testing, antibody screen

Coagulation

Blood cultures if pyrexia or concern of bacterial contamination

Implicated units should be returned to the lab

If mucosal swelling/angioedema/anaphylaxis – IgA testing.

If severe allergy or anaphylaxis consider serial mast cell tryptase measurements

If any respiratory symptoms – CXR

If there are infective/febrile symptoms of moderate severity then the units should be returned to the lab and the blood service informed straight away so any associated units are withdrawn.

All transfusion reactions in the UK, bar mild febrile reactions and allergy, should be reported to SHOT.

Haemolytic transfusion reactions

Acute haemolytic transfusion reactions happen within 24 hours of a transfusion. They are usually related to incompatible red cells, however can occur with plasma.

A secondary immune response to an antigen on the donor red cells causes delayed HTRs. There can also be some bystander haemolysis in these reactions. These will usually occur if a patient had been immunised some time ago and the antibody may now be at such a low level that it is undetectable by antibody screening prior to transfusion. These will produce IgG antibodies within a week of exposure. Delayed HTRs are usually caused by antibodies to Rh, Kidd, Kell, Duffy, MNS antigens. The reason a repeat sample is required after 72 hours if there has been a transfusion within the last month to ensure the production of a new antibody (or the increase in a previously undetectable one) is not missed.

Reactions can occur due to antibodies in patient plasma against antigens on donor cells (major incompatibility), antibodies in donor plasma to patient cells (minor incompatibility), or very rarely, anti bodies in donor plasma to antigens of red cells from another transfused donor product.

Haemolysis occurs by different mechanisms – complete complement activation resulting in intravascular haemolysis, incomplete complement activation and resulting phagocytosis by macrophages of c3b covered cells, cell to cell contact with k cells by IgG covered cells.

The clinical picture of HTR can vary greatly, some patients may have no apparent symptoms, some may have a failure of expected Hb rise following a transfusion while others may have a severe life threatening reaction. Symptoms can include feeling generally unwell, rigors, pain, discomfort around infusion site, nausea/vomitting, diarrhoea, headache, breathlessness, visible haemoglobinuria. Signs can include tachycardia, hypo or hypertension, pyrexia, jaundice, microscopic haemoglobinuria, anuria due to renal failure, bleeding as a consequence of DIC, fall or lower than expected rise in Hb level following transfusion. Given the wide spectrum of signs and symptoms that can occur and the potential for these to be at some time after the transfusion it is also important to consider other potential diagnosis when assessing a patient during/following a transfusion.

The systemic symptoms of HTR can be caused by cytokine release, coagulation cascade activation and fibrinolysis and kinin activation. These can result in a SIRs pictures, DIC, hypotension and renal failure.

Factors that can influence the severity of a reaction can include antibody class. IgG will usually bind at 37 degrees Celsius, as opposed to IgM which normally bind optimally at lower temperatures. A higher number of antigens on the red cell surface will allow greater antibody bonding resulting in greater complement activation. The antibody level is also significant, with greater titres allowing for increased binding with antigens.

When intravascular haemolysis occurs, free haemoglobin can be found in the urine. This occurs when haptoglobin, albumin and haemopexin have been saturated and the excess haemoglobin makes it’s way to the kidneys, where some may not be able to be reabsorbed by the renal tubuli. Although free haemoglobin does pass through the kidney it is thought that the disruptions in micro circulation resulting from the systemic responses to coagulation, fibrinolysis, cytokine and kinin pathway activation are the main cause of the renal impairment that can be seen in HTRs.

As seen in our case a centrifuged fbc sample can show a reddish discolouration of plasma due to the haemoglobin. Urine can also be tested for the presence of free haemoglobin. As in other types of haemolysis, haptoglobins will be reduced and LDH raised. These results should always be interpreted in the clinical context as other conditions can cause these abnormalities. There may or may not be a reticulocytosis depending upon the patient’s underlying bone marrow function. The patient may be jaundiced with a rise in indirect bilirubin.

Pre transfusion, post transfusion and the donor unit should also be taken for evaluation. The DAT on the pre and post transfusion sample as well as blood group and antibody screen should be checked. Crossmatch on the patient’s plasma before and after the transfusion and the donor red cells. If the polyspecific DAT is positive, monospecific DAT should be performed. Antibodies may not be detected initially following a reaction, and samples should be taken and retested over the subsequent weeks to check for appearance of an antibody or positive DAT.

When investigating possible reactions performing an eluate to release the bound antibody from the red cell membrane may be useful in identifying the possible antibody. A variety of serological techniques may need to be employed if the antibody is proving difficult to identify eg enzyme, LISS tube

Preventing reactions

As antibodies can ‘diasappear’ from serological testing, all patient’s should be given an antibody card and units with the corresponding antigen should be avoided in subsequent transfusions. It needs to be noted, and the patient informed, as different hospital blood banks may not have the antibody information from previous antibody investigations so the patient should be empowered to inform people of the antibody every time they may need a transfusion.

Prevention of antibody production through transfusion is important, Rh D is the most immunogenic antigen and wherever possible patient’s should be transfused with RhD compatible blood. There may be situations e.g. emergency situations in males or post menopausal women that RhD positive blood may have to be used if no RhD negative blood is available and a delay would impact on patient care. Sensitisation to other antibodies eg kell is also avoided in pre menopausal women. The appropriate administration of anti-D to women in pregnancy/postpartum has also made huge differences in the incidence of maternal antibody production and subsequently to the rates of HDFN.

To try and prevent antibody production through transfusion in patients who are expected to be multiply transfused over a period of time can have extended red cell phenotyping performed prior to transfusion to try and avoid potentially sensitising antigens.

Our case

In our case the patient was assumed to have an anti C as the cause for the HTR following phenotyping of patient and donor red cells. 5/6 transfused units were C antigen positive, while our patient C antigen negative.

Given that our patient needed further transfusion and had very precarious renal function further reassurance was sought prior to transfusion through nuclear medicine with red cell survival studies. In these studies small volumes (a few mls) of Tc99m labelled donor red cells which are suspect antigen positive and negative are transfused into the patient (on separate days). Serial blood tests at 1,2,3,4 and 24 hours are performed to assess the amount of radioactive material remaining. Gamma camera images can also be taken to see the location of the radioactive material eg in the spleen/urinary tract if being destroyed/excreted, or in the heart if within the circulating blood pool. In our case these showed accelerated destruction of the C positive red cells.

Our patient had a repeatedly negative DAT, this may be been due to all of the transfused red cells being destroyed. Other reasons for negative DAT in haemolysis can be low affinity antibody, red cell body antibody below the level of detection, an antibody (eg IgA or IgM) which the standard DAT will not detect.

The reason for the undetectable C antibody is not known but could be down to a potent antibody at too low a level to be detected by invitro testing. Antibody mediated lymphocytotoxic activation is also been postulated as a cause for HTRs with undetectable antibodies.

There have been several case reports of patients with haemolytic transfusion reactions with undetectable(or difficult to detect) antibodies, therefore if there is a high clinical suspicion of a haemolytic transfusion reaction, if initial investigations are negative further investigation should be undertaken.

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further reading

BSH guidelines – Investigation and management of acute transfusion reactions- H Tinegate et al British journal of haematology 2012 vol 159

https://onlinelibrary.wiley.com/doi/full/10.1111/bjh.12017

Haemolytic transfusion reactions – Erwin Strobel transfusion medicine and haemotherapy.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3076326/#!po=2.11268

Intravascular haemolytic transfusion reaction without detectable antibodies: a case report and review of literature. C.R. Harrison et al 1986 Vox Sang 51:96-101

https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1423-0410.1986.tb00222.x

Haemolytic transfusion reaction due to Rh antibodies detectable only by polybrene and polyethylene glycol technique Lin CK Am J Clin Pathol. 1995 Dec;104(6):660-2.

https://www.ncbi.nlm.nih.gov/m/pubmed/8526209/

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