Stability of red blood cell folate in whole blood and haemolysate.
Folate, a water soluble B vitamin, is necessary for normal cell growth and DNA synthesis. A deficiency leads to megaloblastic anaemia and possible neurological sequelae. Since we receive samples from distant clinics and experience problems due to the long transit times to our laboratory, we carried out a folate stability study. Fasting blood samples were drawn from 40 healthy volunteers. We determined the baseline red blood cell (RBC) folate in duplicate on each sample. Half the sample was then stored at various temperatures prior to haemolysate formation and RBC folate was determined regularly to determine sample stability. The other half was haemolysed, the haemolysate stored at various temperatures and analysed regularly to determine haemolysate stability. A statistical test of equivalence was applied using 18% as a pre-defined limit. We found that whole blood was stable at 4 degrees C up to 72 hours. At room temperature stability has been proven up to 24 hours. Results of additional experiments with haemolysate support stability under all conditions for 12 hours. Samples for RBC folate determination transported from distant clinics are stable for up to 72 hours at 4 degrees C or at room temperature for at least 24 hours. The prepared haemolysates may be stored at -20 degrees C. Our experiments show that sample transportation at higher temperature does not affect folate stability within our predefined limits.