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Quest and Lab Corp. - different Vit. D25 results to this very day

Jacqueline
1 Recommendation

I am told that Quest stopped giving incorrect reports on Vitamin D a year ago. Yet a month ago, I had Quest test my Vitamin D-25, and they reported 47. My
endocrinologist said, "Great." A few weeks later, I was tested by Lab Corp, and they reported 25. I informed my endocrinologist, and she said sometimes labs use different methods. Her advice was to choose on or the other, take 2000 units daily of D, then test at the same lab in a month and always test at the same lab from now on. How can that help me to know if one of the labs is testing incorrectly? I have severe osteoporosis and need to know what to do or to whom to report this. My doctor's advice makes no sense to me. Any suggestions?

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18 replies

Jacqueline

I just realized I referred to my Vitamin D test
incorrectly. The test I took was 25-hydroxyvitamin D.
Your help will be very much appreciated.

rmchavin

Dear Jacqueline:

I'm not an expert on vitamin D but one possibility is that both labs reported your blood vitamin D levels correctly. If you swallowed a large dose of calcium pills inbetween the 2 blood tests, then it may have been the calcium which dramatically lowered your blood vitamin D levels. In this PubMed study on how calcium and dairy products may cause advanced prostate cancer in men, note how it says close to the bottom of the paragraph: "In a sample of this cohort, higher calcium intake was associated with lower circulating 1,25(OH)2 vitamin D levels." http://www.ncbi.nlm.nih.gov/pubmed/16492906?ordinalpos=1&itool=EntrezSystem 2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DiscoveryPanel.Pubmed_Discovery _RA&linkpos=3&log$=relatedarticles&logdbfrom=pubmed The other possibility is that one of the two labs measured your blood vitamin D levels incorrectly. If you suspect this, then you should continue to measure your blood vitamin D levels at both labs on the exact same day (from now on, if you can afford it).

bethanyb

I don't know if this helps, but I came across this recent article by Dr. Mercola and he recommends vitamin D testing by LabCorp not Quest. He doesn't give specifics on why.

bethanyb

I'm not sure how to edit my previous post. I meant to include this link:
http://articles.mercola.com/sites/articles/archive/2009/05/23/Can-Calcium-A ctually-Make-Your-Bones-Weaker.aspx

Jacqueline

I want to thank those who replied to my post. I am surprised I got so few replies, since this is vital. I don't know to whom to report this problem or what my Vitamin D count really is. Please help.

Chirp

Hi Jacqueline,

You've probably already done this, but make sure both tests are the same exact VitD test and make sure the results are reported in the same units.

I've heard (for a different test; I think it was 24 hr urine for Calcium) that there are "differences" in some labs' results, certainly "differences" in the range of measures that are called "normal/reference," and I was told they use different "reference groups" ... I don't really know if it's because different equipment is used or what. It makes no sense to me, though, because I'd then read information (elsewhere, in publications etc) about optimum levels for that test, citing a particular "target value" as though all labs' tests are standardized so the results are comparable!

It must be frustrating to have this spread in your VitD test results... Are the "normal/reference ranges" shown on both reports to be the same values? If I had this happen to me, I'd call each lab and ask questions... and/or call the lab at the hospital (or wherever you gave the sample) and ask them. There might be some interesting answers! You could also ask how the labs are standardized and/or certified, to find out who might oversee these kinds of problems (if there's definitely a problem).

If you don't get any satisfaction, if all lab people say the numbers are directly comparable and you're quite certain it's not possibly your actual levels, one way to "get to the bottom" is to do a VitD test at 3 labs from the same sample day. You'd then see if all are "same" or not. If one is not like the other 2, you'd have a better idea which lab to avoid, I'm thinking. But ("ideal world") this kind of thing shouldn't be necessary!!!

I'm surprised that "one month" is recommended as a testing interval although I have no basis that I can cite at present to support this. Do you have a target number/range in mind? I take well over 2000iu/day and my Endo didn't even look at that info, best I can tell. My January test was 50 (I forget the units and don't have paper here, but that's the minimum of where I want to be), and I'm not yet worried that it will be "too much too soon."

Perhaps you can ask your Endo if you can safely increase your supplement rate in case the low number is correct... but without overdoing it in case your high number is correct. (If she's not worried over the results difference, I wonder what she thinks your level actually is! Is she treating you as though it's the low# or the high#? Would it matter?! I wonder what she makes of this...)

Here's a link to a site that explains a lot about labs and lab tests; this particular page begins a section on lab quality
http://www.labtestsonline.org/lab/labquality.html
(I see another topic covers "reference ranges"; I'll check that out!)

At any rate, keep up the VitD and try not to stress over the lab data. Certainly it will shake out sooner or later and meanwhile you can work on getting your numbers up! I'm hoping you'll share whatever you learn about this. It would be very interesting to learn more about how much the labs can "vary" and/or how much our bodies can vary (like over an increase in calcium as per rmchavin's post). I hadn't thought these kinds of variations would be significant...

Jacqueline

Thanks, Chirp, for the time and caring you put into your fine reply. I very much appreciate it.

Jeffrey22

I am also interested in the accuracy of Vitamin D tests and have been doing some research. I found the following link that explains the differance between Qwest and Lab corp.

http://preventdisease.com/news/08/090308_vit_d.shtml

I think it is worth a look.

Cheers..

SequoiaHealth

Hi Jacqueline:
2000 iu a day is not much vitamin D considering most experts say we use 4000 iu a day average. I have a client who took 6000 iu D3 for 6 months and went from 25 ng/mL to 36 ng/mL. I suggest to clients that they discontinue all supplements 3 days prior to testing to eliminate false positives.

I would also suggest looking into the home vitamin D tests offered by many companies. They are reported to be very accurate. That way you get a third opinion. Dr. Cannell has them available. http://www.vitamindcouncil.org/

Hope this helps.

Woody McMahon
NOVA Osteoporosis Support Group Leader

Chirp

Hey Jeffrey22, that's a great find---there seems to be a real eye-opener herein...

Got me looking closer at other resources online, and to a discussion here back in January (when Quest was on the hot seat for inaccuracies).

It seems that there are *different* *methods* used for VitD testing (the 25OHD aka 25 hydroxyvitamin D).

One method, "RIA," was typically used in the studies that have served to tell us what "levels" of VitD are better for us.

There's another method, "LIASON," that gives results very similar to those of RIA, so it's fine to compare LIASON test results with recommendations based on RIA test results. (It seems Lab Corp uses LIASON.)

However, there's also the (newer) "LC-MS/MS" method, which yields results that are *not* comparable with the others; they're typically (always?) lower! (They also can split out D2 and D3 which can be a good thing it seems.) Quest uses this method.

Apparently, Mayo Clinic and ZRT also use LC-MS/MS, but it seems they "calibrate" results so that they are comparable to those from the RIA or LIASON methods.

According to Dr Cannell at vitamindcouncil.org, as of 1/9/09 Quest was not calibrating their results to make them comparable to RIA. He recommends dividing Quest result by 1.3. A Quest 47 would become a 36!

But wait---Dr Mercola says to multiply a Quest result by 0.6, making a Quest 47 only 28!

A ZRT Labs document claims the average RIA measure is 20-30% lower than a LC-MS/MS measure of same sample (making a Quest 47 be in the 33-38 range).

I think it makes sense to bypass Quest and any who provide non-comparable results---unless a physician wants the D2 & D3 split out and/or can convert the values! Then, whatever the Lab we use, we need to find out whether or not the results are comparable with the RIA method. (And if not, find out if the lab will provide a "converted" value that is comparable --- or "convert" your target so you know when you're there.) Then, stick with one lab (for simplicity).

I'm really surprised that this kind of thing is going on!

Zeta brought the Cannell/Quest info to a discussion here http://www.inspire.com/groups/national-osteoporosis-foundation/discussion/v itamin-d-testing-problem/ I didn't read it closely then because I don't use Quest.

I'm going to find out about the method used by my Lab, and Jacqueline I really appreciate that you brought this topic up again!

(Also on a Quest site it says "fasting is preferred" for this test. Hmmm...)

Here are some of the links I checked:

http://laboratory-manager.advanceweb.com/Editorial/Content/Editorial.aspx?C C=191618

http://mbnpa.org/files/documents/VitaminD/AccuracyInTestingVitaminD.pdf

http://www.questdiagnostics.com/hcp/topics/endo/vitamin_d.html

http://www.curezone.com/forums/fm.asp?i=1345487 (or perhaps see http://articles.mercola.com/sites/articles/archive/2009/01/20/the-overwhelm ing-evidence-that-sunlight-fights-cancer.aspx )

http://www.ajcn.org/cgi/reprint/87/4/1087S.pdf

vitamindprescription

I personally take 5000 IU of vitamin D and the last time I checked my blood level, I was at 44 ng/ml (normal is 32-100 ng/ml). A study by Dr. Reinhold Vieth showed that up to 10,000 IU could safely be taken without any hypercalcemia.

I recently had a patient with a vitamin D level of 5 ng/ml (nl 32-100). I recommended 10,000 IU daily for 6 weeks then 6000 IU daily. She came back to see me 2 months later and told me she was incorrectly taking 30,000 IU (as drops) DAILY for 2 months. I rechecked her blood immediately and was surprised to learn she was still within normal range. Her level was 92. These labs were done at labcorp.

Eric Madrid

sylvia6789

Hi Jacqueline et al,

Two years ago, Quest conducted a blood test for me, showing high glucose. My doctor told me to repeat the test, and go to LabCorp this time. Not sure if she just wanted a second (i.e. different) data point or that she likes LabCorp better. Yes, the results were different. LabCorp said that I was fine and not diabetic. However, I avoided sugar for 2 days prior to the second test.

btw, Does anyone know the correlation between Vitamin D and Calcium in the blood? Please advise.

I made a mistake a week ago in asking for the vitamin D test ... I called my Doc. and requested a blood test, for vit. D. The receptionist sent the req. for a "Comprehensive metabolic panel" which she said should include vit. D, in addition to the lipid panel (cholesterol)..." I didn't know any better and gave blood for the test. Then, when I met with my doc, I saw that the comp. panel gave many measurements, but not vitamin D. My Calcium level is good. It's 9.6 (the range is 8.5 to 10.6 mg/dL So, my Doc. said that I can get the vitamin D level test next time. Since I have high cholesterol, I need to modify my diet and have another blood test in 6 months. Now, I have the req. in my hand, " Vitamin D, 25-Hydroxy" for the next test ;-) Meanwhile, I will take 800 to 1000 IU of vit. D.

Thanks and have a good day,
Sylvia

rmchavin

Dear sylvia6789:

Fortunately, the diet that you need to follow to improve your good cholesterol to bad cholesterol ratio is essentially the same diet that you need to follow to maintain healthy bones: Minimize your consumption of animal-source protein, animal-source vitamin A, salt, salted/pickled/barbequed/grilled/fried/smoked foods, caffeine, phosphoric acid (cola drinks), and alcohol. Greatly increase your consumption of fruits, vegetables, soy, and green tea. Don't smoke. Swallow one 2,000 IU vitamin D pill daily. Plant-source vitamin A will not harm you. For your supply of heart-healthy omega-3 fatty acids, either eat high-fat fish regularly and/or swallow fish oil pills or krill oil pills every day. http://www.inspire.com/groups/national-osteoporosis-foundation/discussion/a dvantages-of-getting-your-vitamin-d-from-high-fat-fish-instead-of-pills/ Light, weight-bearing exercise will greatly benefit your bones and heart if you can keep on exercising your whole life. Unfortunately, almost everybody quits their exercise program sooner or later. Eating foods high in free radicals, such as salted/pickled/barbequed/grilled/fried/smoked foods, will oxidize your LDL (bad) cholesterol and cause heart disease and stroke. For people who have developed Type 2 adult-onset diabetes, follow the same diet and lifestyle that you would for optimal bone and heart health. To lower your HbA1c and fasting blood glucose number, use the biguanide, Glucophage (metformin). Avoid using any drugs that are classified as sulfonylureas. Prolonged use of sulfonylureas will, in time, "burn out" your pancreas and this will be equivalent to partially converting your less severe Type 2 adult-onset diabetes into resembling the more severe Type 1 juvenile diabetes. If Glucophage alone isn't able to lower your blood sugar and HbA1c adequately, then continue to swallow the maximum allowable dosage of Glucophage but swallow also the minimum dosage of the thiazolidinedione, Actos (pioglitazone). Type 2 diabetics who haven't already "burned out" their pancreas by prolonged use of a sulfonylurea can very likely permanently cure (untrigger) their Type 2 diabetes by (1)following the bone-and-heart-healthy diet, (2)losing at least 30% of the amount that they are overweight by, and (3)swallowing these 2 prescription drugs daily.

sylvia6789

Hi rmchavin,

Thank you for your very informative recommendations for a diet which will improve our bones, lower our bad cholesterol, and help us from becoming diabetic. It's great that the paths to all three goals are the same. However, it's not a easy path, as the "forbidden" foods are so tempting. This is going to take a lot of discipline!

I do look forward to good results from LabCorp in a few months.

Thanks again,
Sylvia

smlhealth

Hi Jaqueline:
Go to the website www.vitamindcouncil.com
There is a multitude of information available on Vitamin D, including suggestions for what to look for in a lab test.
Keep me posted on your success.
Good luck!

smlhealth

Hi Jacqueline:
Just a correction on my last message. The email address for the vitamin D council is www.vitamindcouncil.org (not .com)
For anyone reading this message, this site is an amazing source of information regarding the importance of Vitamin D 3.

Jacqueline

Thanks, smihealth. That is an excellent site. By the
way, there is an important new posting in our community today about potassium. I hope everyone reads it.

millie123

It's now October of 2009. Dr. Mercola's most recent newsletter explains that, to solve the discrepancy between Lab Corp and Quest Vitamin D test, divide the Quest result by 1.3 to get a more accurate result.

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