Table 3.
Reference intervals of vitamin B6 metabolites stratified by age and sex.
| Variable | Age group | Sex | n | Median (Q1, Q3) | P2.5 (95%CI) | P97.5 (95%CI) |
|---|---|---|---|---|---|---|
| PLP (nmol/L) | <50 years | Male | 103 | 38.44 (26.22, 50.54) | 10.36 (7.49–16.91) | 145.87 (84.12–150.60) |
| Female | 87 | 39.65 (27.43, 56.85) | 13.03 (7.08–17.03) | 103.46 (71.05–115.04) | ||
| ≥50 years | Male | 94 | 31.68 (23.91, 40.54) | 9.27 (8.21–14.16) | 142.96 (79.11–166.95) | |
| Female | 83 | 41.38 (31.08, 50.17) | 16.83 (15.58–20.11) | 173.06 (122.80–189.85) | ||
| PL (nmol/L) | <50 years | Male | 103 | 14.66 (11.25, 17.65) | 7.18 (6.10–8.61) | 49.95 (26.74–66.34) |
| Female | 87 | 14.78 (11.61, 17.95) | 7.48 (7.12–9.33) | 37.87 (24.65–52.11) | ||
| ≥50 years | Male | 94 | 14.00 (11.01, 16.27) | 6.58 (5.08–8.14) | 54.62 (30.87–65.87) | |
| Female | 83 | 16.99 (14.24, 19.92) | 7.78 (6.34–9.99) | 71.43 (37.75–72.74) | ||
| PA (nmol/L) | <50 years | Male | 103 | 15.67 (12.94, 18.07) | 8.19 (6.39–10.21) | 47.66 (32.32–67.21) |
| Female | 87 | 15.23 (11.68, 18.84) | 8.03 (5.84–8.68) | 35.60 (27.52–44.61) | ||
| ≥50 years | Male | 94 | 17.25 (13.76, 21.35) | 9.23 (7.53–10.26) | 46.35 (31.34–66.11) | |
| Female | 83 | 18.45 (14.14, 22.87) | 9.34 (7.32–11.25) | 52.90 (34.72–54.43) | ||
| PLP/PL | <50 years | Male | 103 | 3.79 (2.94, 4.69) | 1.72 (1.38, 2.19) | 6.25 (5.78, 6.89) |
| Female | 87 | 3.77 (3.22, 4.25) | 2.18 (1.43, 2.62) | 6.00 (5.05, 6.19) | ||
| ≥50 years | Male | 94 | 3.37 (2.82, 3.96) | 1.87 (1.73, 2.05) | 4.95 (4.71, 6.04) | |
| Female | 83 | 3.57 (2.89, 4.11) | 2.05 (2.00, 2.36) | 5.26 (4.99, 5.32) | ||
| PLP/PA | <50 years | Male | 103 | 3.27 (2.27, 4.21) | 1.03 (0.80–1.52) | 6.95 (5.81–7.36) |
| Female | 87 | 3.50 (2.35, 4.49) | 1.71 (1.18–1.90) | 7.74 (6.05–10.28) | ||
| ≥50 years | Male | 94 | 2.64 (1.87, 3.36) | 0.76 (0.57–1.34) | 5.38 (4.63–8.25) | |
| Female | 83 | 3.25 (2.32, 4.23) | 1.46 (1.28–1.85) | 6.42 (5.11–7.73) | ||
| PAr | <50 years | Male | 103 | 0.26 (0.19, 0.33) | 0.12 (0.12–0.14) | 0.61 (0.48–0.76) |
| Female | 87 | 0.25 (0.18, 0.32) | 0.11 (0.08–0.14) | 0.44 (0.40–0.50) | ||
| ≥50 years | Male | 94 | 0.31 (0.24, 0.39) | 0.15 (0.10–0.17) | 0.89 (0.56–1.17) | |
| Female | 83 | 0.26 (0.19, 0.32) | 0.13 (0.10–0.16) | 0.48 (0.39–0.53) |
The robust method based on Horn’s algorithm was used to calculate 95% reference intervals (P2.5–P97.5), and their stability was validated via nonparametric bootstrap resampling. PLP, pyridoxal 5′-phosphate; PL, pyridoxal; PA, 4-pyridoxic acid.