TABLE 3.
Geometric mean concentration (95% CI) by treatment (processed within 2 hours or 24 hours) and sample type (EDTA, LH, or serum)1, 2
| 2-hour processing | 24-hour processing | |||||
|---|---|---|---|---|---|---|
| Sample type | Sample type | |||||
| Analyte | EDTA | LH | Serum | EDTA | LH | Serum |
| Clinical markers | ||||||
| C-reactive protein, mg/L | 1.75 (1.14–2.70)a | 1.45 (0.94–2.24)b | 2.00 (1.30–3.07)a | 1.81 (1.17–2.78)a | 1.46 (0.95–2.24)b | 1.93 (1.26–2.97)a |
| Ferritin, μg/L | 47 (30–72)a | 49 (32–76)b | 49 (32–76)b | 48 (31–74)a | 49 (32–76)b | 49 (32–76)b |
| Creatinine, μmol/L | 72.8 (68.0–78.0)a | 75.8 (70.8–81.1)b | 75.7 (70.8–81.0)b | 73.8 (69.0–79.0)a | 75.8 (70.8–81.1)b | 76.2 (71.2–81.5)b |
| Triglycerides, mmol/L | 1.21 (0.88–1.65) | 1.16 (0.85–1.58) | 1.18 (0.86–1.61) | 1.19 (0.87–1.62) | 1.18 (0.87–1.62) | 1.18 (0.86–1.61) |
| HDL cholesterol, mmol/L | 1.30 (1.31–1.59)a | 1.38 (1.13–1.68)b | 1.38 (1.13–1.68)b | 1.30 (1.06–1.58) a | 1.35 (1.10–1.64)2,b | 1.36 (1.12–1.67) b |
| Total cholesterol, mmol/L | 4.72 (4.28–5.20)a | 4.86 (4.41–5.35)b | 4.92 (4.46–5.42)b | 4.71 (4.28–5.19)a | 4.83 (4.38–5.32)b | 4.94 (4.48–5.44)c |
| Fat-soluble vitamins | ||||||
| 25-hydroxyvitamin D, nmol/L | 32 (25–41)a | 34 (26–43)a,b | 35 (27–44)b | 33 (25–42) | 33 (26–42) | 33 (26–43) |
| Retinol, μmol/L | 1.43 (1.30–1.58)a | 1.57 (1.42–1.73)b | 1.53 (1.38–1.69)a,b | 1.43 (1.29–1.58)a | 1.57 (1.42–1.73)b | 1.57 (1.42–1.73)b |
| α-tocopherol, μmol/L | 24.1 (21.5–27.1)a | 26.0 (23.2–29.2)b | 25.6 (22.8–28.8)b | 24.4 (21.7–27.4)a | 25.7 (22.9–28.9)b | 25.8 (23.0–29.0)b |
| γ-tocopherol, μmol/L | 1.30 (1.16–1.47)a | 1.40 (1.24–1.57)b | 1.38 (1.23–1.55)b | 1.33 (1.18–1.49)a | 1.39 (1.24–1.57)a,b | 1.41 (1.25–1.58)b |
| Lutein, μmol/L | 0.33 (0.27–0.40)a | 0.37 (0.30–0.44)b | 0.36 (0.29–0.43)b | 0.33 (0.28–0.40)a | 0.36 (0.30–0.44)b | 0.36 (0.30–0.44)b |
| β-cryptoxanthin, μmol/L | 0.19 (0.14–0.26)a | 0.21 (0.16–0.28)b | 0.20 (0.15–0.27)b | 0.19 (0.4–0.26) | 0.20 (0.15–0.27) | 0.20 (0.15–0.27) |
| Lycopene, μmol/L | 0.87 (0.72–1.05)a | 0.95 (0.78–1.14)b | 0.92 (0.76–1.11)a,b | 0.89 (0.74–1.08) | 0.92 (0.76–1.10) | 0.91 (0.75–1.09) |
| α-carotene, μmol/L | 0.15 (0.12–0.19)a | 0.17 (0.13–0.21)b | 0.17 (0.13–0.21)b | 0.15 (0.12–0.19) | 0.16 (0.13–0.20) | 0.16 (0.13–0.20) |
| β -carotene, μmol/L | 0.59 (0.40–0.86)a | 0.64 (0.44–0.94)b | 0.62 (0.43–0.91)b | 0.61 (0.42–0.89) | 0.62 (0.43–0.91) | 0.61 (0.42–0.89) |
| Minerals | ||||||
| Selenium, μg/L | 77 (72–82)a | 80 (75–85)b | 79 (74–84)b | 76 (72–81)a | 80 (75–85)b | 79 (74–84)b |
| Zinc, μg/L | 812 (778–847) | 800 (767–834) | 802 (769–837) | 817 (783–853)a | 844 (810–881)2,b | 812 (779–847)a |
| Water-soluble vitamins | ||||||
| ETKAC (thiamin) [ratio] | 1.11 (1.08–1.15) | 1.10 (1.07–1.13) | n/m | 1.10 (1.07–1.14) | 1.10 (1.07–1.13) | n/m |
| EGRAC (riboflavin) [ratio] | 1.35 (1.26–1.45) | 1.35 (1.26–1.45) | n/m | 1.35 (1.26–1.45) | 1.34 (1.25–1.43) | n/m |
| PLP (vitamin B-6), nmol/L | 51.9 (39.7–67.7) | 49.6 (38.0–64.8) | 52.1 (39.9–68.0) | 54.0 (41.4–70.5)a | 45.9 (32.5–59.9)2,b | 44.9 (34.4–58.6)2,b |
| PA (vitamin B-6), nmol/L | 20.1 (15.9–25.3)a | 20.9 (16.6–26.3)a,b | 21.5 (17.1–27.2)b | 20.2 (16.1–25.5) | 21.4 (17.0–27.0) | 20.5 (16.3–25.9) |
| Total folate, nmol/L | 16.2 (12.3–21.4)a | 17.0 (12.9–22.5)b | 17.0 (12.9–22.4)b | 15.9 (12.1–20.9)a | 16.7 (12.6–21.9)b | 17.2 (13.0–22.6)c |
| Vitamin B-12, ng/L | 401 (336–479)a | 393 (330–469)a | 380 (319–453)b | 388 (326–463)2,a | 394 (330–470)a | 373 (313–445)b |
| Holotranscobalamin, pmol/L | 68 (55–84)a | 63 (51–78)b | 77 (62–95)c | 74 (60–91)2,a | 66 (53–82)b | 74 (60–91)a |
| Vitamin C, μmol/L | 55 (45–67) | 58 (48–71) | 57 (47–70) | 31 (26–38)2,a | 59 (49–72)b | 58 (47–70)b |
The 24-hour processed samples were mailed, cooled overnight after collection, and processed on arrival at the laboratory. All analytes were measured in plasma or serum except for ETKAC and EGRAC (measured in saline-washed red blood cells). Geometric means with uncommon letters are significantly different (P < 0.05) from other sample types within treatment (2-hour or 24-hour processing). Abbreviations: EGRAC, erythrocyte glutathione reductase activation coefficient; ETKAC; erythrocyte transketolase activation coefficient; LH, lithium heparin plasma; n/m, not measured, sample type not suitable for analysis; PA, 4-pyridoxic acid; PLP, pyridoxal-5-phosphate
Significantly different from 2-hour processed sample.