THE VITAMIN B12 AND FOLATE PATHOLOGY INVESTIGATION
THE INVESTIGATION OF ERRORS IN PATHOLOGY TESTS
FOR VITAMIN B12 AND FOLATE DEFICIENCY
BY MEANS OF MEDICAL EXPERIMENTS
B12 AND FOLATE INFORMATION
B12 NOTES
Serum B12
Tests
MMA - Serum vs Urine
Treatment
Sources of Information

Index

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Advantages and Disadvantages

Although I use serum MMA tests, I do not suggest that this is best for every patient. The choice will depend on what is available in your location, as well as consideration of the advantages and disadvantages of each.

There are three claimed advantages of the MMA urine test, compared to the serum :

  • Less invasive; does not require needle
  • Not affected by renal problems
  • More sensitive

Norman Clinical Laboratories recommends, and offers, only urinary MMA tests. I suggest that you visit their web site for detailed information; their site is at link D1 on the Site Links page.

This test is also recommended by Sally M. Pacholok and Jeffrey J. Stuart in their book Could It Be B12? An Epidemic of Misdiagnoses, reference DB01 on the References page.

These are some arguments in favour of the serum test:

  • Can be collected at same time as other blood samples; use same sample as used for homocysteine test
  • Renal problems can be eliminated by other tests
  • Precision of serum tests is excellent if sufficient care is taken by the lab

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Why I use Serum MMA

There are only five labs in Australia that claim to be able to do the MMA assay.

The two in Brisbane, Mater Pathology and QHPS, were incapable of even a minimal standard of performance in 2005-2006. The one lab in Western Australia will not accept samples from interstate. The lab in Adelaide, Women's and Children's Hospital (WCH) did a good job of four samples sent there in late 2005, but cannot test tHcy, and are very expensive. That leaves the the NSW Biochemical Genetics Service at the Children’s Hospital Westmead, in Sydney.

Although Westmead offers the urinary MMA test, I have not needed to consider using it and do not know how precise it is. Their lab uses Stable Isotope Dilution Tandem Mass Spectrometry, for serum MMA, which is the reference method used by Mayo Labs. The quality of their results, for my own samples, for serum MMA has been excellent.

Because I have blood tests for the other three analytes, total B12, HoloTC and tHcy, it is also convenient for me also to have the MMA tested from the same samples as used for tHcy.

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Why Some Serum MMA Tests Have Been Unreliable

I am not convinced that the serum MMA assay is intrinsically less sensitive, precise or accurate than the urine assay. Certainly, the results of serum MMA testing, from the two Brisbane labs, Mater Pathology and QHPS, contained very significant errors that I attribute to poor quality control.

Westmead, which tested the samples last, did consistently produce the same results for each identical sample within many sample pairs. This proved firstly that the other two labs had made very serious analytical errors, and secondly that serum MMA testing can be done with adequate precision if the lab takes sufficient care with quality control.

The unsatisfactory performance of laboratories testing MMA has been well documented. One study, reference AE13 on my References page, concludes:

Conclusions: No method differences were found, but significant among-laboratory imprecision was found in the present study. Improvements are needed to reduce the analytical imprecision of most laboratories, and attention must be focused on calibration issues. Differences among laboratories can be improved by introducing high-quality reference materials and by instituting external quality assessment programs

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