Page 346 - Vitamin D and Cancer

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15 Assessment of Vitamin D Status in the 21 Century 333
marketed on their ability to separately measure 25(OH)D and 25(OH)D in a blood
2 3
sample. Clinically, however, there is no advantage to this separate measurement
claim. Not a single scientific publication exists that demonstrates separate 25(OH)
D and 25(OH)D measurements are superior to a “total” 25(OH)D value as
2 3
supplied by the DiaSorin tests. In fact, this separate reporting has been shown to
confuse the clinician [21]. The truth is, LC/MS laboratories report separate values
because that is how LC/MS technology has to report the data [17–20] and is not a
reason to “spin” it into a clinical advantage. The fact is, this individual quantitation
has been going on for the past 3 decades utilizing HPLC detection and no one
claimed it to be clinically advantageous. Some LC/MS laboratories have actually
billed inappropriate CPT codes to enhance return for these separate reported values.
I consider this practice to be abusive and fraudulent and feel it must end. Further,
99% of all patient samples assayed will not contain any 25(OH)D
2.
Replacement of FDA-controlled devices such as the DiaSorin and IDS assays
with “home-brew” LC/MS assays from a clinical diagnostic standpoint is, again,
disturbing. It is disturbing because the DiaSorin assays have and continue to be the
standard of clinical 25(OH)D assessment. I can say this because the “normal”
range of circulating 25(OH)D is almost entirely based on clinical studies using the
DiaSorin tests. In fact, Labcorp (Burlington, NC) uses a publication by Hollis [2]
on which to base their clinical range of 25(OH)D levels. In turn, this publication
is based on DiaSorin assay-based clinical studies so unless a given LC/MS method
is calibrated against the DiaSorin methods, this reference range should not be
reported against.
Many years and clinical studies have gone into establishing the DiaSorin reference
range and as we stated earlier, this consists of thousands of scientific publications. To
prove my point we have selected some large significant clinical studies on which the
“normal” circulating level of 25(OH)D is based, most of which utilized DiaSorin and
some IDS assays as their method of analysis. I have not included any LC/MS clinical
studies because basically none exist, which is my point exactly.
The DiaSorin RIA has been used to generate all of the 25(OH)D data from the third
National Health and Nutrition Examination Survey (NHANES III). I have included
selected references on this topic to validate my claim [22–51]. Many more studies
from NHANES exist with respect to vitamin D and all use the DiaSorin RIA. Studies
from the huge NIH sponsored Women’s Health Initiative (WHI) used the DiaSorin
LIAISON assay for the first two major publications [49, 50] with others to follow.
The Harvard-based studies, the Health Professionals’ Follow-up Study (HPFS)
and the Nurses’ Health Study (NHS) have been used to establish much of the infor-
mation in the last decade with regard to the relationship of circulating 25(OH)D
levels and various disease states such as cancer, autoimmune, cardiovascular and
renal. All of these studies again utilized DiaSorin-based assays [29–48]. Of course,
we cannot forget the relationship of vitamin D status, PTH and skeletal integrity.
Hundreds of papers have been published on this topic; most using DiaSorin assays
none using LC/MS testing.
What then should LC/MS laboratories do? If they are going to use the current
DiaSorin-based reference range [2] they had better target their values to that of the