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 | 2.57 (1.99, 3.17) | 1.16 (0.93-1.48) | 4.23 (3.88-4.66) |
| Female | 87 | 2.55 (2.18, 2.88) | 1.47 (0.97-1.77) | 4.06 (3.42-4.18) | ||
| ≥50 years | Male | 94 | 2.28 (1.90, 2.68) | 1.27 (1.17-1.39) | 3.34 (3.18-4.09) | |
| Female | 83 | 2.41 (1.96, 2.78) | 1.39 (1.35-1.59) | 3.56 (3.37-3.60) | ||
| PLP/PA | <50 years | Male | 103 | 2.42 (1.68, 3.12) | 0.76 (0.59-1.14) | 5.15 (4.35-5.45) |
| Female | 87 | 2.60 (1.74, 3.33) | 1.27 (0.88-1.41) | 5.73 (4.51-7.62) | ||
| ≥50 years | Male | 94 | 1.96 (1.38, 2.49) | 0.57 (0.43-1.00) | 3.99 (3.46-6.12) | |
| Female | 83 | 2.41 (1.72, 3.13) | 1.08 (0.95-1.37) | 4.76 (3.79-5.73) | ||
| PAr | <50 years | Male | 103 | 0.32 (0.24, 0.40) | 0.15 (0.15-0.18) | 0.69 (0.58-0.86) |
| Female | 87 | 0.30 (0.22, 0.37) | 0.14 (0.10-0.17) | 0.54 (0.48-0.56) | ||
| ≥50 years | Male | 94 | 0.38 (0.28, 0.47) | 0.19 (0.13-0.21) | 1.03 (0.66-1.37) | |
| Female | 83 | 0.32 (0.24, 0.39) | 0.16 (0.13-0.19) | 0.57 (0.47-0.61) |
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.