Table 2.
Sources of pre-analytical variability.
| Technical sources |
| Specimen and mode of sample collection |
| Specimen handling and storage |
| Thermodegradation |
| Photolysis |
| Timing of sample collection (see also diurnal variation) |
| Between laboratory variation |
| Biological (subject related) sources |
| Age: |
| Puberty, somatic growth, menopausal transition, menopause, ageing, frailty |
| Gender |
| Ethnicity |
| Recent fractures (up to one year) |
| Pregnancy/Lactation |
| Drugs: |
| Anti-resorptive agent (e.g. HRT, bisphosphonates, SERMs, strontium, OPG) |
| Anabolic agents (e.g. anabolic steroids, PTH, PTHrP, strontium) |
| Glucocorticosteroids |
| Anticonvulsants |
| GnRH agonists |
| Oral Contraception |
| Non-skeletal Disease: |
| Diabetes |
| Thyroid disease |
| Renal impairment (GFR < 20 ml/min/1.73 m2) |
| Liver disease |
| Systemic inflammatory disease (IBD, RA, COPD etc.) |
| Degenerative joint disease |
| Immobility/Loss of gravity (bed rest, space flight) |
| Diet |
| Exercise |
| Temporal variability: |
| Diurnal (circadian) |
| Menstrual |
| Seasonal |