TABLE 1.
Analytical methods and variation, biological variation, and quality specifications for nutritional and selected clinical biomarkers
| Variation, %3 | Quality specifications, %4 | ||||||
|---|---|---|---|---|---|---|---|
| Analyte | Method1 | Analytical2 | Interindividual | Intraindividual | Optimum | Desirable | Minimum |
| Clinical markers | |||||||
| C-reactive protein | Clinical Chemistry Analyzer | 1.7 | 76.35 | 42.25 | 10.9 | 21.8 | 32.7 |
| Ferritin | 4.2 | 15.05 | 14.96 | 2.6 | 5.3 | 7.9 | |
| Creatinine | 0.6 | 18.76 | 6.86 | 2.5 | 5.0 | 7.5 | |
| Triglycerides | 0.9 | 56.86 | 28.86 | 8.0 | 15.9 | 23.9 | |
| HDL cholesterol | 1.6 | 28.36 | 12.46 | 3.9 | 7.7 | 11.6 | |
| Total cholesterol | 1.2 | 22.36 | 8.26 | 3.0 | 5.9 | 8.9 | |
| Fat-soluble vitamins | |||||||
| 25-hydroxyvitamin D | LC-MS/MS | 3.3 | 37.96 | 11.35 | 4.9 | 9.9 | 14.8 |
| Retinol | HPLC | 4.1 | 30.76 | 9.56 | 4.0 | 8.0 | 11.6 |
| α-tocopherol | 3.6 | 35.16 | 11.36 | 4.6 | 9.2 | 13.8 | |
| γ-tocopherol | 6.7 | 51.06 | 12.16 | 6.6 | 13.1 | 19.7 | |
| Lutein | 5.7 | 46.06 | 17.46 | 6.1 | 12.3 | 18.4 | |
| β-cryptoxanthin | 5.7 | 58.86 | 20.56 | 7.8 | 15.6 | 23.4 | |
| Lycopene | 7.5 | 47.46 | 26.16 | 6.8 | 13.5 | 20.3 | |
| α-carotene | 6.9 | 54.37 | 35.86 | 8.1 | 16.3 | 24.4 | |
| β -carotene | 5.6 | 67.46 | 24.26 | 9.0 | 17.9 | 26.9 | |
| Minerals | |||||||
| Selenium | ICP-MS | 5.6 | 13.26 | 5.16 | 1.8 | 3.5 | 5.3 |
| Zinc | 4.2 | 12.77 | 9.38 | 2.0 | 3.9 | 5.9 | |
| Water-soluble vitamins | |||||||
| ETKAC (thiamin) | Enzymatic | 2.5 | 4.87 | 3.79 | 0.8 | 1.5 | 2.3 |
| EGRAC (riboflavin) | Enzymatic | 1.5 | 13.77 | 3.29 | 1.8 | 3.5 | 5.3 |
| PLP (vitamin B-6) | HPLC | 5.0 | 34.06 | 20.05 | 4.9 | 9.9 | 14.8 |
| PA (vitamin B-6) | 5.0 | 66.87 | 67.010 | 11.8 | 23.7 | 35.5 | |
| Total folate | LC-MS/MS | 2.8 | 64.36 | 22.66 | 8.5 | 17.0 | 25.6 |
| Red cell folate | Microbiological | 6.5 | 35.86 | 9.15 | 4.6 | 9.2 | 13.9 |
| Vitamin B-12 | Immunoassay | 3.6 | 43.66 | 13.46 | 5.7 | 11.4 | 17.1 |
| Holotranscobalamin | ELISA | 4.2 | 41.87 | 13.011 | 5.5 | 10.9 | 16.4 |
| Vitamin C | Fluorescence | 3.4 | 31.06 | 26.06 | 4.4 | 8.7 | 13.1 |
Assay equipment or principles are listed in the table. Full details of the methods can be found in the Supplemental Methods. Abbreviations: EGRAC, erythrocyte glutathione reductase activation coefficient ETKAC, erythrocyte transketolase activation coefficient; ICP-MS, inductively coupled plasma mass spectrometry; PA, 4-pyridoxic acid; PLP, pyridoxal-5-phosphate.
Analytical precision was obtained from methods as used in the UK National Diet and Nutrition Survey Rolling Programme (13).
The inter- and intraindividual percentage variations were used to calculate the quality specifications. Data sources are described in relevant footnotes.
Quality specifications were derived from inter- and intraindividual variations, as described by Fraser et al. (22).
Chen et al. (21).
Lacher et al. (47).
UK National Diet and Nutrition Survey (13).
González-Revaldería et al. (48).
van Dokkum et al. (49).
Bor et al. (50).
Brokner et al. (51).