CAtion leakage from RED cells (CARED)

Summary

This study called ‘CARED 3’ will be looking at rare genetic variants that cause familial pseudohyperkalaemia (FP) which means “falsely elevated potassium in blood”. An individual with FP does not show symptoms because at body temperature cells behave normally and FP is not thought to affect the individual’s health or wellbeing.  

Normally, red blood cells actively pump potassium in and out of the cell to regulate the potassium levels. Red blood cells from donated blood are stored in the fridge for up to 35 days prior to transfusion. When red cells are stored in the fridge after donation, this active pumping process slows down, so potassium slowly leaks outside the cell into the surrounding liquid. In FP, when the red blood cells are cooled, they leak out more potassium more quickly than red blood cells without FP. The transfusion of large amounts of potassium could have negative consequences for vulnerable patient groups such as infants and babies. We do not routinely identify whether donors have FP, so their blood donations could contain unexpectedly high levels of potassium that may cause harm if transfused to certain patients.  

We have already identified the rate of potassium build up in the blood bag of FP red blood cells over the 35-day storage period in an earlier study called CARED 2. In that study we tested 6 FP individuals and 11 gender and age-matched control individuals (no FP) who consented for the study. We confirmed that FP red cell units do have significantly higher potassium levels than controls during most of the storage period (35 days) in the fridge. Importantly, the potassium from FP red cells is released at a fast rate early in storage reaching near maximal levels by day 3 of storage. On day 7, FP red cells had more than 3 times the average potassium levels of control red cells, while at the end of storage (day 35), they were not much higher than control. Apart from the changes in potassium, red cells from FP individuals behaved similarly to red cells from individuals without FP. We are currently conducting a risk assessment to better understand the potential consequences of FP donations for recipients of blood transfusions to inform future policies on whether routine testing of donations for FP is warranted. 

Red blood cells are sometimes irradiated before transfusion to inactivate any residual white cells in the units, which may cause unwanted outcomes in transfusion for certain recipients. Irradiation is already known to increase the release of potassium from standard red blood cells. It is not known if this effect is exacerbated in FP red cells or if indeed the FP red cells might be more vulnerable to irradiation damage in other ways. The aim of this study is to examine the effect of irradiation on the potassium levels and other parameters of FP red blood cells. This research will determine the quality and safety of irradiated red cells from FP donors.   

We are requesting individuals who have FP and individuals who don’t have FP (control) to kindly donate a unit of whole blood so that we can study the effect of irradiation on the quality parameters of red cells over cold storage. We would be very pleased to receive repeat donations from the same volunteers that donated to the previous study CARED 2, but hope to also recruit additional volunteers to broaden the scope of the CARED 3 study. 

Participation: 14 volunteers from the Cambridge BioResource took part in this study. The study participants attended an appointment at the NHS Blood and Transplant service and gave 1 unit of blood.

Organisation: This study was organised by Dr Rebecca Cardigan the NHS Blood and Transplant service.