Comparison of Three Blood tests

I do weekly blood tests. I use a few labs for complex historical reasons and I wanted to run a test where a sample taken through the same needle was sent to three labs simultaneously. I think there are important lessons from this that are useful to people. Labs tend to have slightly different panels, but I have stuck to the default panel. I will not identify the labs. I had the blood taken at about 10.20am on 3rd November and I drove the sample to the first lab. I am not sure when they started the test, but I got the results at 5.15pm via my GP so they must have been sent out something like 5pm. The second sample went via a courier and I had the results on Friday 4th November at 17.10 again this was via my GP so they would have been produced a bit earlier. The third lab went via post and the results were available by 6.53pm today.

I am not going to give all the results from all the tests. The units are UK units and I will generally give a result when I had a result from two or more labs.

Haemoglobin g/L 144/144/145 - happy with this
RBC count E12/L 4.49/4.55/4.59 - not as good but not too bad. Delays cause problems for blood cell values
MCV fl 96.1/94.1/95.9 - I wonder if the labs with delay bodge their figures a bit for the delay. This varies a bit too much for my liking.
MCH pg 32.1/31.6/31.6 - OK
MCHC g/l 33.5/33.6/33 - OK
RDW 12.8/12.9/12.9 - OK
Platelets E9/L 173/190/178 - this is a bit varied
WCC E9/L 2.83/2.95/3 - a bit varied
Neutrophils 1.83/1.98/1.97 - a bit varied
Lymphocytes 0.7/0.69/0.71 - OK
Monocytes 0.25/0.26/0.28 -
Eosinphils 0.01/0/0 - ok
Basophils 0.02/0.02/0.02 - perfecto
Na 136.8/140/? - not really happy with this as it is an ion
K 4.8/4.7.? - ok
Urea 4.39/4.6/4.9 - looks like this goes up with time before testing.
Creatinine 73.43/83/93 - this is one that makes me really unhappy because it is clear that testing delays cause the variation.
Bilirubin 6.73/7/6.5 - ok ish
ALP 74.15/67/69
AST 24.63/20/?
ALT 22.73/19/18
GGT 22.73/24/23
Total protein 60.05/67/68
Albumin 38.54/42/38.7
Globulin ?/25/29.3 - too much variation
Ca 2.28/2.3/? - ok
Phosphate 1.26/1.12/? this metabolises
Uric Acid 316.33/298/306
Triglyceride 1.6/1.7/1.74
Cholesterol 4.71/4.7/4.86
HDL 1.73/1.7/2.95 - that last figure looks wrong
LDL 3.01/2.2/2.42 - this also makes me uncomfortable as to the later two labs although it may be that the first is wrong. Still too much variation.
Fe ?/14.9/14.3
TIBC ?48/46.7
Ferritin 176.7/298/291 - these do seem to be the same units and the variation is far too high. My guess is that this is intransit metabolism.
I got an HbA1C from the third lab that is out of kilter with my other HbA1C values and I think is caused by in transit metabolism.
Free Thyroxine 15.16/17.3/17.2
25OHD 147.18/153/147

In conclusion. This gives me a figure I can use to adjust prior values from the same labs to give an inter lab comparison. I knew there were problems with metabolism and Creatinine, but it appears there are other similar problems.

I have not tried to research Ferritin metabolism, but it strikes me that there may be an issue there.

The cholesterol figures are particularly concerning particularly that people get quite excited about this figure. I wonder if it gets metabolised away in transit, but the variation is too big. Looking at the total cholesterol, however, is appears to be a question of deciding what is LDL and what is not.


Thanks for doing this John. It is important to know how close values are to what they really are and this is the only way.

Actually I think they did pretty good. I’m impressed by the labs and you, good job.

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The labs with delays should warn people about the unreliable values.

I have reviewed the history of my HbA1c tests and correlated this to the delays in testing. I estimate that one day’s delay in testing results in the % going up by about 0.5. My lowest HbA1c result this year was 4.18% equivalent to 22 mmol/mol. This was one where I took the sample to the lab and it was tested within an hour or two.

The highest was the one where the test took a few days and was 5.3% 34 mmol/mol. This sort of thing worries me (as does creatinine) because people rely on this data to identify whether or not they have T2 diabetes (or CKD) and it could clearly produce false positives.

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