Vitamin D is a hormone, synthesized by the skin, the liver, and then
metabolized by the kidney to an active hormone, calcitriol. An excess of
vitamin D may lead to hypercalcemia. Vitamin D deficiency may lead to a
variety of disorders. This LCD identifies the indications and limitations of
Medicare coverage and reimbursement for these services.  
  
Vitamin D is called a "vitamin" because of its availability from an exogenous
source, predominantly from oily fish in the form of cholecalciferol, vitamin
D3. Plant-based vitamin D is in the form of ergocalciferol, Vitamin D2. It is
really a hormone, as it is synthesized by the skin, metabolized by the liver,
and converted by the kidney to an active hormone, calcitriol. Calcitriol in
its classical action, absorbs calcium from the intestine, and promotes bone
mineralization.  
  
In the skin, 7-dehydrocholesterol is converted to vitamin D3 in response to
sunlight, a process that is inhibited by sunscreen with a skin protection
factor (SPF) of 8 or greater. Once in the blood, vitamin D2 or D3 from diet,
or D3 from skin production are carried by an alpha-2-globulin, vitamin D
binding protein, and are carried to the liver where they are hydroxylated to
yield 25-hydroxyvitamin D (25OHD; calcidiol). 25OHD then is converted in the
kidney to 1, 25(OH)2D (calcitriol) by the action of 25OHD-1-alpha hydroxylase
(CYP27B1). The CYP27B1 in the kidney is regulated by nearly every hormone
involved in calcium homeostasis, and its activity is stimulated by PTH,
estrogen, calcitonin, prolactin, growth hormone, low calcium levels, and low
phosphorus levels. Its activity is inhibited by calcitriol, thus providing the
feedback loop that helps regulates its synthesis.  
  
An excess of vitamin D is unusual, but may lead to hypercalcemia. Vitamin D
deficiency may lead to a variety of disorders; the well-described is rickets
in growing children or osteomalacia in adults. Evaluating the status of a
patient's vitamin D sufficiency is accomplished by measuring the level of
25-hydroxyvitamin D. Measurement of other metabolites is generally not
necessary outside of several unusual metabolic bone disorders or in chronic
kidney disease-mineral bone disorder (CKD-MBD).  
  
 **Indications:**  
Measurement of vitamin D levels is indicated for patients with:

  * chronic kidney disease stage III or greater;
  * osteoporosis;
  * osteomalacia;
  * osteopenia;
  * osteogenesis imperfecta;
  * osteosclerosis;
  * hypocalcemia;
  * hypercalcemia;
  * hypoparathyroidism;
  * hyperparathyroidism;
  * rickets;
  * vitamin D deficiency to monitor the efficacy of replacement therapy;
  * fibromyalgia;
  * granuloma forming diseases;
  * hypovitaminosis D;
  * hypervitaminosis D;
  * long term use of anticonvulsants or glucocorticoids and other medications known to lower - vitamin D levels;
  * malabsorption states;
  * obstructive jaundice;
  * cirrhosis;
  * psoriasis;
  * Paget's disease of bone;
  * gastric bypass;
  * obesity.

**Limitations:**  
For Medicare beneficiaries, screening tests are governed by statute (Social
Security Act 1861 {nn}). Vitamin D testing may not be used for routine
screening.  
  
Assays of calcitriol need not be performed for each of the above conditions.
The most common type of vitamin D deficiency is that of 25 OH Vitamin D.  
  
The 1,25-dihydroxy form of vitamin D is generally only required to assist in
the diagnosis of certain cases of rare endocrine disorders (primary
hyperparathyroidism, hypothyroidism, pseudohypoparathyroidism), or for
diagnosing and treating renal osteodystrophy and vitamin D-dependent and
vitamin D resistant rickets, or in cases of unknown causes of hypercalcemia,
including sarcoidosis. Level of both 25OHD and calcitriol are not needed as a
panel for determining a patient's vitamin D status or to monitor routine
vitamin D replacement therapy for most diseases. It is expected that the
medical record will justify the tests chosen for a particular disease entity,
that all available components of 25 OH vitamin D and other metabolite levels
will not be performed routinely on every patient, and that supportive
documentation for test choices will be available to the Contractor upon
request.  
  
This Contractor does not expect to receive billing for the various component
sources of 25 OH vitamin D separately (such as stored D or diet derived D).
Only one total 25 OH vitamin D assay (comprising the sum of both 25OHD2 and
25OHD3) will be considered for reimbursement on any particular day, if
medically necessary, for the patient's condition.

Once a beneficiary has been shown to be vitamin D deficient, further testing
may be medically necessary only to ensure adequate replacement has been
accomplished for this vitamin deficiency, although, generally, other
parameters are measured. Annual testing of the vitamin D status may be
appropriate depending upon the indication and other mitigating factors.
Because there can be variability in individual 25OHD responses to supplemental
vitamin D in high-risk individuals, the serum 25OHD levels could be retested
after about 3 months of supplementation to confirm that the target 25OHD level
has been reached. If the follow up test shows they have not yet reached the
target level, the test can be repeated in another 3 months until the target
level is achieved.  
  
Testing Methods  
Several methods are available for measuring circulating concentrations of
25-OH-D. Medicare will cover laboratory tests that give practitioners accurate
and reliable information. The method used to perform this testing should be
validated.