The effect of different methods of storage on the results of serum total CO2 assays.

Metabolic acidosis frequently complicates end-stage renal failure. In haemodialysis patients its severity is usually monitored by measurement of the total CO(2) (TCO(2)) level. Samples from 'satellite dialysis' patients are often stored prior to analysis. We investigated the affect of storage of 21 samples for 24 h under different conditions prior to analysis. If samples were stored at room temperature the TCO(2) fell from 22.7+/-4.2 mmol/l to 21.6+/-3.7 mmol/l (P=0.001). If the same samples were spun and stored at 4 degrees C the TCO(2) was 22.4+/-3.9 mmol/l (P=not significant). We conclude that the magnitude in the fall of TCO(2) stored at room temperature for 24 h is unlikely to be clinically significant and can be prevented by spinning the sample and refrigerating it.