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
THE METHYLMALONIC ACID INVESTIGATION
MMA ERRORS
Summary
Laboratory Performance
QHPS
Interpretation Errors

Index

This page contains the following sections:

You can go to a section by selecting the link.

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Introduction

Here you will find my specific claims about what I consider to be the poor performance by Queensland Health Pathology Service, Brisbane (QHPS)

For each issue raised, I explain:

  • What Went Wrong
  • Why it Matters

Notes for Charts and Tables

Where a chart is shown, you can view a larger chart in a new window by selecting the link shown above the chart.

Where there is a link to a table, above a chart, you can view the complete Excel table in a new window.

Tables will initially appear at low resolution in the new window. To enlarge the table to full size, move the cursor from the white space below the table to inside the lower right corner of the table; an icon will then appear in the lower right corner of the table. Click on the icon to view the table full-size. Use the horizontal scroll-bar, in the new window, to view the entire table.

The chart and table numbers used here correspond to the sheet numbers in the Excel file, Series 1 - Serum B12 Investigation, which may be downloaded from Evidence.

These results can be verified from the scanned original pathology reports, available on this site from Evidence.

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QHPS MMA - Errors

Summary of What Went Wrong

There were very significant differences between QHPS results for identical samples, and between QHPS results and Westmead results for the same samples.

The important points to note, about MMA levels for Sample A and Sample B, from these QHPS results are:

  • The maximum difference between Sample A and Sample B, for any pair was 3.84 SD.
  • Four results out of 10 pairs were outside the 95% Confidence Interval.
  • Three of those results were also outside the 99.0% Confidence Interval.
  • None of those results were also outside the 99.9% Confidence Interval.

The important points to note, about MMA levels, from the QHPS Sample A and Westmead Sample Mean results are:

  • The maximum difference between the labs was 6.87 SD.
  • Eight results out of 15 were outside the 95% Confidence Interval.
  • Five of those results were also outside the 99.0% Confidence Interval.
  • Two of those results were also outside the 99.9% Confidence Interval.

I am confident that the Westmead results are correct because:

  • For each sample pair, there was no significant difference between the two samples; this is the expected result because Sample A should be identical to Sample B.
  • There is a consistent increasing trend in the MMA level, as would be expected during the onset of vitamin B12 deficiency.
  • Westmead uses Stable Isotope Dilution Tandem Mass Spectrometry, the reference method also used by Mayo Medical Laboratories.
  • Westmead quotes a CVA of 0.015 umol/L for MMA, consistent with satisfactory performance, for the known CVW of 0.31 umol/L.

I am confident that the QHPS results are incorrect because:

  • For four sample pairs, there was a significant difference between the two samples; this is NOT the expected result because Sample A should be identical to Sample B.
  • There is no consistent increasing trend in the MMA level; such a trend would be expected

Why it Matters

QHPS failed to report the onset of an actual vitamin B12 deficiency.

Westmead reported my MMA levels increasing during 2006, after I ceased taking oral B12. Here is a chart showing how QHPS reported my MMA levels, compared to Westmead, for the group A samples:

Chart D16 Table B2

The Westmead results show a consistently increasing MMA level, exceeding the Westmead cut-off between 24 February and 5 June 2006, then remaining above it. This means that I was consistently vitamin B12 deficient, by the very latest, after 5 June 2006.

The QHPS results include erratic variations that are inconsistent with the trend shown by the Westmead results, obscuring the true rising trend of my MMA levels. Although nowhere as erroneous as the Mater Pathology results, the QHPS results do not meet the quoted imprecision, or the standard required to diagnose or monitor vitamin B12 deficiency.

Because of these false variations, and an absence of the actual consistently increasing trend of the MMA level, QHPS failed to report the onset of vitamin B12 deficiency.

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QHPS MMA - Delays

Summary of What Went Wrong

The important points to note, about timeliness for QHPS were:

  • 10 of the 15 group A samples took more than seven days to process.
  • Of those, two samples took 36 days to process.
  • 15 of the 19 group B samples took more than 7 days to process.
  • Of those, 10 samples took more than 14 days to process.
  • Of those, two samples took more than 21 days to process.

QHPS did report instrument failure in September but this could not account for all of the delays.

Why it Matters

While monitoring my cellular vitamin B12 status, it was important to receive results within a reasonable time. Because of the risk of permanent nerve damage, it was necessary to avoid entering a B12 deficient state.

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QHPS MMA - Failed to Comment About Excessive MMA Levels

Summary of What Went Wrong

There was never any comment made on any of the QHPS reports about the excessive MMA levels. The high results were highlighted in bold, but nothing else:

Why it Matters

What is important here is the context in which QHPS were performing these tests. They were well aware that I was seeking evidence to support my claim that I did have a vitamin B12 deficiency; a constructive comment from the pathologist would have made a useful contribution to my efforts.

The absence of a constructive comment is particularly significant in the context of the problem raised in the next section.

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QHPS MMA - Misleading Comments in Reports

Summary of What Went Wrong

The QHPS pathology reports included two comments that were, in my opinion, potentially misleading.

I shall consider these two comments separately:

"Different methodologies used for the measurement of methylmalonate should be taken into account if considering interlaboratory comparisons."

These are the methods used, and the quoted CVA, for each of the three labs where my MMA was analysed in 2006:

-
Westmead
QHPS
Mater
Method
LC - MS / MS
LC - MS / MS
GC - MS
Quoted CVA %
5.9% at 0.26 umol/L
6.2%
-
Quoted SD
0.015 umol/L
-
0.03 umol/L

The CVA quoted by MP is not even consistent with the requirement for minimum performance.

Is this because of different methodologies, or is it because of failure of quality control at Mater Pathology?

GC-MS has been successfully used by other labs to measure serum MMA, for the diagnosis and monitoring of vitamin B12 deficiency since the method was described by Stabler et al, reference AE02, in 1986.

Indeed, the Metabolics Lab at the Women's and Children's Hospital in Adelaide (WCH), where four of my samples were re-tested successfully, uses GC-MS..

The variations in results between labs has been investigated by several researchers, who found no significant difference between methods.

Pfeiffer et al, reference AE13, reported these results:

and came to these conclusions:

"We note the prolonged storage time before our analysis of this sample, which should be taken into consideration."

Methylmalonic acid is not affected by the storage times involved in my investigations.

According to expert opinion, samples may be stored for at least five years, if frozen at -70 C, and can withstand at least five freeze/thaw cycles. Here is what Centres for Disease Control (CDC) Laboratory Procedure Manual for Methylmalonic Acid, reference AE20, says about this:

Why it Matters

As for the previous section, what is important here is the context in which QHPS were performing these tests.

Why did the Director of QHPS go to the trouble to make these two comments, that I would not expect to see in a pathology report, when he had made no comment about the excessive MMA levels?

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