Table 2.
Effect of delayed processing of whole blood stored at 32°C for up to 3 d prior to processing on serum folate concentrations1
| Analyte | Serum folate concentration2 | Relative change3 | |||||
|---|---|---|---|---|---|---|---|
| Reference | 1 d | 2 d | 3 d | 1 d | 2 d | 3 d | |
| nmol/L | % | ||||||
| tFOL | 49.5 (40.4, 60.7) | 44.0 (35.9, 53.9) | 38.7 (31.6, 47.5) | 33.6 (27.4, 41.2) | −11.1** (−13.7, −8.38) | −21.7** (−24.0, −19.3) | −32.0** (−34.0, −29.9) |
| 5-MethylTHF | 40.3 (32.6, 49.9) | 25.8 (20.9, 31.9) | 19.7 (15.9, 24.4) | 15.2 (12.3, 18.8) | −36.0** (−42.7, −28.4) | −51.2** (−56.3, −45.4) | −62.3** (−66.3, −57.9) |
| Folic acid | 2.21 (1.13, 4.31) | 2.26 (1.16, 4.42) | 2.24 (1.14, 4.37) | 2.28 (1.17, 4.45) | 2.44 (−2.03, 7.12) | 1.37 (−3.05, 6.00) | 3.21 (−1.30, 7.92) |
| MeFox | 2.07 (1.65, 2.60) | 9.24 (7.37, 11.6) | 10.4 (8.26, 13.0) | 10.7 (8.51, 13.4) | 346** (294, 405) | 400** (342, 466) | 415** (356, 483) |
1
Serum from promptly processed whole blood frozen at −70°C was used as reference; statistical analysis by 1-way ANOVA. 5-methylTHF, 5-methyltetrahydrofolate; MeFox, pyrazino-s-triazine derivative of 4α-hydroxy-5-methyltetrahydrofolate; tFOL, total folate.
2
Values are geometric means (95% CI), n = 21
3
Values are percent change (95% Cl) compared to reference
**
P <0.0001