Taurine concentrations in plasma and whole blood in humans: estimation of error from intra- and interindividual variation and sampling technique.

The "normal" physiological taurine status in human plasma and whole blood was evaluated for day-to-day variation. Because plasma taurine concentrations can vary by greater than or equal to 100% because of sampling and analytical techniques, various blood-collecting and -handling procedures were compared to ascertain the most reliable method for measuring plasma taurine. Blood collection into EDTA-wetted plastic syringes at room temperature proved most reliable. Plasma and whole-blood taurine concentrations were determined in the same 13 women and 11 men three times within a 10-d period. The normal plasma taurine concentration was 44 +/- 9 mumol/L (mean +/- SD; n = 40) in fasting subjects and 42 +/- 7 mumol/L (n = 30) in semi-fasted individuals, with an intraindividual variation of 9 +/- 5%. Whole-blood taurine concentrations ranged from 164 to 318 mumol/L and had an intraindividual variation of 11 +/- 5%. Inter-individual variation averaged 12 +/- 7% for plasma and 7 +/- 6% for whole blood taurine. Because plasma and whole-blood taurine concentrations were not correlated, assessment of both would provide the most accurate estimate of taurine status. Short of that, whole-blood taurine would appear to be the best single measure.