PHLEBOTOMISTS : LabPlus DOES NOT accept patient payment for Vitamin D testing.
The only exception to this is Non-residents where all tests are paid for.
This test may be vetted by a pathologist.
The clinical information for the test must be clearly written on the request form. If clinical information is not provided, or does not provide sufficient justification for the test, the test may be declined.
Declined tests :
If a test is declined, the specimen will be held for a reasonable period (usually 3 weeks but dependant on the stability of the sample). Medical practitioners seeking approval for a declined test should email the on-call Chemical Pathologist ( chemicalpathologist@adhb.govt.nz ) , giving the patient's name and NHI number and the clinical justification for the test. If unable to email, call the on-call Chemical Pathologist via Lablink (09-3078995) and identify yourself as a doctor.
Units : nmol/L
Reference interval:
|
< 25 |
Moderate to severe vitamin D deficiency |
|
25 - 50 |
Mild vitamin D deficiency |
|
50 - 150 |
Optimal target range for bone health |
|
> 250 |
Vitamin D intoxication has been reported above this level, but is rare at levels < 500 nmol/L. |
Uncertainty of measurement : 12%
Conversion factor : ng/mL x 2.5 = nmol/L
Principle : Direct competitive chemiluminescence
Assay : 25OH Vitamin D Total
Analyser : Diasorin Liaison XL
Vitamin D toxicity
Vitamin D intoxication may occur at levels above 250 nmol/L.
Vitamin D deficiency
The main source of vitamin D is the action of sunlight in the skin. Low plasma vitamin D is common, especially among darker skinned people of all age groups, and those who are sunlight-deprived for any reason. Vitamin D concentrations are lowest during winter, and low vitamin D tends to recur each winter in susceptible individuals. The half-life of 25-hydroxy vitamin D in plasma is 3 months.
Most people with low vitamin D are asymptomatic. If prolonged and severe, vitamin D deficiency may lead to rickets in children and osteomalacia in adults; these are uncommon conditions. The role of low vitamin D as a contributing factor to osteoporosis is still a matter of debate. Overall evidence from RCT's suggests that supplementation with vitamin D does not have consistent benefits for fracture prevention (3,8). It is not necessary to routinely measure vitamin D in patients with low bone density.
Individuals who are at risk of symptomatic vitamin D deficiency are those of Indian or African descent, frail institutionalized elderly, and those who avoid sunlight for cultural or medical reasons. In such individuals, vitamin D supplementation is reasonable without blood testing. There is insufficient evidence to support routine vitamin D supplementation or testing vitamin D levels in healthy community-dwelling individuals.
Pregnancy: Available evidence does not suggest that pregnant women are at increased risk of vitamin D deficiency compared with the nonpregnant population (7). Current guidlines do not support routine testing of vitamin D levels in pregnancy (6)
Treatment of Vitamin D Deficiency
Adults : Cholecalciferol 1.25 mg (50,000 units) per month. Bolus dosing of vitamin D might be harmful.
Children (<15 years):
The formulation and dosage of Vitamin D supplements for children depends on the indication and should be discussed with a paediatrician.
Calcitriol (Rocaltrol) or Alfacalcidol (One Alpha) should NOT be used to treat vitamin D deficiency, except in specific disorders ( e.g. chronic renal disease).
Labplus Policy on vitamin D testing
From Sept 2011 Labplus has had a policy with restrictions on vitamin D testing. Vitamin D tests were originally developed for investigation of rickets, osteomalacia and other metabolic bone disorders. In recent years the number of requests for vitamin D tests has increased dramatically. Most of these requests are unrelated to metabolic bone disease, and have arisen because of reported associations between various disease states (cancers, cardiovascular disease, diabetes, autoimmune disorders and infectious diseases) and lower vitamin D concentrations.
However, a causal link has yet to be demonstrated for any of these conditions (1-4). The Institute of Medicine, following an comprehensive review of the evidence, concluded that " For extraskeletal outcomes, including cancer, cardiovascular disease, diabetes, and autoimmune disorders, the evidence was inconsistent, inconclusive as to causality, and insufficient to inform nutritional requirements. Randomized clinical trial evidence for extraskeletal outcomes was limited and generally uninformative." (2) .
A recent comprehensive literature review for the Ontario Ministry of Health has concluded that there is little evidence that it is useful to test vitamin D concentrations in patients without symptoms of metabolic bone disease. (5)
The following criteria apply to vitamin D tests at Labplus. The test will be performed only when:
1. Ordered by the following specialists: endocrinologist, gastroenterologist, bariatric surgeon, rheumatologists and nephrologists
2. Ordered for specific high risk groups for rickets/osteomalacia (e.g. cystic fibrosis, proven malabsorption, bariatric surgery, refugees, deeply pigmented skin, full veil wearers)
3. Ordered for the investigation of rickets/osteomalacia, disorders of calcium and phosphate metabolism, or osteoporosis
4. All requests on children (less than 16 y ) will be approved.
5.
Ordered for other patients after discussion with, and approval by, a Labplus Chemical Pathologist
The indication (reason) for the test must be stated on the request form
(e.g. "hypocalcemia" or "cystic fibrosis")
Labtests (a private community laboratory) are able to perform the vitamin D test if the patient wishes to pay for it. A separate request form is required and must contain the words 'patient to pay'. If you require this test performed by Labplus (Auckland Hospital) at public expense, please search "pathologist" in this Test Guide for the procedure for obtaining pathologist approval.
References
1. Autier, P., M. Boniol, et al. (2014). "Vitamin D status and ill health: a systematic review." Lancet Diabetes Endocrinol 2 (1): 76-89.
2. Ross AC, Manson JE, Abrams SA et al. The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine: what clinicians need to know. J Clin Endocrinol Metab.
2011;96:53-58
3. Reid, I. R., M. J. Bolland, et al. (2014). "Effects of vitamin D supplements on bone mineral density: a systematic review and meta-analysis." Lancet 383 (9912): 146-155.
4. Vitamin D supplementation: navigating the debate. Best Practice Journal (BPAC). 2011:26-35
5. Clinical utility of vitamin D testing: an evidence-based analysis. Ont Health Technol Assess Ser [Internet].www.health.gov.on.ca/english/providers/program/mas/tech/reviews/pdf/rev_vitamin%
20d_201002.pdf. Vol. 10: Medical Advisory Secretariat. , 2010:1-95
6. ACOG Committee Opinion No. 495: Vitamin D: Screening and supplementation during pregnancy. Obstetrics and gynecology 2011;118(1):197-8.
7. Rosen CJ, Abrams SA, Aloia JF, Brannon PM, Clinton SK, Durazo-Arvizu RA, et al. IOM Committee Members Respond to Endocrine Society Vitamin D Guideline. J Clin Endocrinol Metab 2012;97
(4):1146-52.
8. Bolland, M. J., A. Grey, et al. (2014). "The effect of vitamin D supplementation on skeletal, vascular, or cancer outcomes: a trial sequential meta-analysis." Lancet Diabetes Endocrinol 2 (4): 307-320.
Emails to chemicalpathologist@adhb.govt.nz will receive priority attention from the on-call chemical pathologist.
If the query concerns a specific patient please include the NHI number in your email.
If email is not a suitable option, please contact the on-call chemical pathologist via Lablink (Auckland City Hospital ext. 22000 or 09-3078995).
Individual chemical pathologists may be contacted but will not be available at all times.
After-hours : contact Lablink (Auckland City Hospital ext. 22000 or 09-3078995) or hospital operator for on duty staff after hours.
Dr Samarina Musaad (Clinical Lead) : SamarinaM@adhb.govt.nz ext. 22402
Dr Cam Kyle: CampbellK@adhb.govt.nz ext 22052
Dr Weldon Chiu: WeldonC@adhb.govt.nz ext. 23427
Dr Campbell Heron: CHeron@adhb.govt.nz ext. 23427
Dr Sakunthala Jayasinghe: Sakunthala@adhb.govt.nz ext. 23427
Stability:
Stable for 5 days at 4oC
Freeze if arrival at LabPlus will be longer
This test may require Chemical Pathologist approval.