Comparison of capillary finger stick+venous blood sampling for 34 routine chemistry analytes: potential for hospital+remote blood sampling

[helvella]

The validity of tests using fingerprick blood samples has long been questioned. Some claiming they are unusably awful. Others claiming tests are as good as those done on venous blood.

It is good to see a paper which has researched the questions.

Unfortunately, while they did include TSH, they did not cover FT4, FT3 and several other frequently discussed analytes.

Also, they call the samples "capillary" and, while that is a proper term, it is a shame that there is the possibility of confusion with samples obtained using devices like Tasso which are sometimes expressly called capillary devices. Hopefully there will be further research covering Tasso and similar devices.

And the good news? Broadly, fingerprick tests can be pretty good!

Comparison of capillary finger stick and venous blood sampling for 34 routine chemistry analytes: potential for in the hospital and remote blood sampling

Martijn J.H. Doeleman , Anne-Fleur Koster , Anouk Esseveld , Hans Kemperman , Joost F. Swart , Sytze de Roock and Wouter M. Tiel Groenestege ORCID logo EMAIL logo

From the journal Clinical Chemistry and Laboratory Medicine (CCLM)

doi.org/10.1515/cclm-2024-0812

Abstract

Objectives

This study examined the comparability of venous and capillary blood samples with regard to routine chemistry analytes.

Methods

Venous and capillary blood samples were collected from adult patients to assess comparability of alanine transaminase, albumin, alkaline phosphatase, apolipoprotein B, aspartate aminotransferase, total bilirubin, calcium, chloride, creatin kinase, creatinine, C-reactive protein, ferritin, folic acid, free T4, gamma glutamyltransferase, glucose, high density lipoprotein cholesterol, iron, lipase, lipoprotein a, magnesium, phosphate, postassium, prostate specific antigen, sodium, total cholesterol, total protein, transferrin, triglycerides, thyroid stimulating hormone, urate, urea, vitamin B12 and 25-hydroxyvitamin-D3. Furthermore, hemolysis-icterus-lipemia Index (HIL-Index) was measured for all samples. All measurements were performed using the Siemens Atellica® CH or IH Analyzer. Deming regression analysis and mean relative differences between venous and capillary measurements of each analyte were contrasted with the desirable total allowable error (TEa) and Clinical Laboratory Improvement Amendments (CLIA) 2024 proposed acceptance limits for proficiency testing.

Results

Deming regression and mean relative differences demonstrated excellent comparability between venous and capillary samples for most measured analytes.

Conclusions

Capillary and venous samples showed comparable results for almost all studied chemistry analytes. Of the 33 studied analytes for which TEa criteria where available, 30 met TEa criteria. CLIA 2024 criteria where available for 29 of the studied analytes of which only glucose did not meet the criteria. In conclusion, capillary blood draw is a suitable alternative for venous blood sampling for measuring most of the investigated analytes. This benefits patients with fear of needles and might pave the way for remote self-sampling.

Keywords: chemistry analytes; capillary sampling; finger stick; comparability; remote blood sample collection; alternative blood sampling

Open access here:

degruyter.com/document/doi/...

[tattybogle]

fT4 is on the list ..... or am i being thick ?

[helvella Administrator in reply to tattybogle]

No - that's my role.

I split my reading across the day and made a mistake.

[TSH110 in reply to helvella]

but no FT3 ☹️

[TSH110 in reply to tattybogle]

But FT3 is the most important one and it’s not there! Can we assume it’s accurate if the others are? I assume not.

[helvella Administrator in reply to TSH110]

Seems likely but I don't think it safe to assume anything!

[TSH110 in reply to helvella]

My thoughts too it's a real shame they didn’t test it

[helvella Administrator in reply to TSH110]

How about emailing them? I feel it is often worth pointing things out or asking why not. The worst that can happen is you don't get a reply.

[TSH110 in reply to helvella]

Good idea - we should all email them about it so they know in no uncertain terms it’s a big omission that’s really let us down

[TSH110 in reply to helvella]

Ok I’ve done it and emailed them about their omission of free t3 and asked them address it in any future reach of a similar nature.

If I hear back I’ll let you know what they have to say.

[TSH110 in reply to helvella]

The response was fast and looks like it could well be included in future studies, More likely with more requests for it perhaps? :

Dear [TSH110],

I can understand your disappointment. Validating capillary blood draw for various analytes is an ongoing process. Unfortunately it is not possible to measure every analyte in a small (capillary) sample volume. For future capillary studies we are thinking about validating a larger endocrine analyte panel.

Met vriendelijke groet,

Wouter Tiel Groenestege

Clinical chemist, PhD, MEd | Division Laboratories, Pharmacy and Biomedical Genetics, Central Diagnostic Laboratory, Staff Clinical diagnostics

University Medical Center Utrecht | Room number G03.548 | Internal mail no G03.550 | P.O. Box 85500 | 3508 GA UTRECHT

[e-mail]

M: [phone] | umcutrecht.nl/ | Workdays: Absent on Tuesday

[TSH110 in reply to helvella]

Have now responded to thank them for their speedy response and to say I hoped they would to not only think about it but actually do it and I’m looking forward to reading the results in a scientific paper in due course. I included a link to explain the situation for us (a lot better than I can explain ) and said I hoped they would take the time to have a look at it, as it was well written and referenced. A Tania special,

Can’t do much more.

[TSH110]

useful to know. I’ve had problems with foliate and one other with the finger prick test

[helvella Administrator in reply to TSH110]

For folate, I don't think it is the draw that is the problem - more the time and possible damage between the draw and the analysis.

[TSH110 in reply to helvella]

Yeah they said the cells had exploded or similar I did struggle to get the sample out which would not have helped. Even with the downward plank method they were no good either.

but my venous draws with NHS have read it ok Perhaps they are better transported by the nhs rather than via the mail system?

[TiggerMe Ambassador in reply to TSH110]

Squeezing the finger is often where the damage occurs

[TSH110 in reply to TiggerMe]

Yes I had to do a lot of that - my blood clots almost immediately and it’s like trying to get it from a stone not a finger 🤣🤣🤣

helvella

[Hectorsmum2 in reply to TSH110]

I take an asprin about an hour before I do mine or I would never get the blood out..

[TSH110 in reply to Hectorsmum2]

Oh that’s an interesting solution to it thanks for the tip

[helvella Administrator in reply to Hectorsmum2]

It might be an idea to read this post I've just made!

Variable effects of nonsteroidal antiinflammatory agents on thyroid test results

healthunlocked.com/thyroidu...

I wouldn't want you to get a misleading result.

[BB001]

For TSH, fT4 and fT3, I've done both: 1) NHS GP and MonitorMyHealth fingerprick, 2)NHS GP and medichecks fingerprick.

Both private companies gave virtually the same result as NHS GP. For those of you who are wondering, when it is really important to know the result of my latest change in my T3 dosing, I also use a private company in case the NHS lab doesn't do the fT3 and fT4 tests (despite my GP requesting them).

[Zephyrbear in reply to BB001]

I always do a private Medichecks test whenever I have an NHS one done. Thankfully my daughter is a qualified midwife and can do a venous draw for me on the same morning as my NHS one, just a couple of hours earlier. Quite reassuring how one matches the other reasonably well.

[Judithdalston in reply to Zephyrbear]

The health assistant, or whoever, at my Gps just fills my extra ‘private’ phial(s) from the same needle in my arm…takes a few extra seconds. No problem, though sometime asked ‘why?’ Generally check what the Gp has asked to be tested, normally just TSH, so easy to say want FT4/3, vit/mins etc as not done by NHS. Nice to see tiny difference in NHS and private lab. results from same blood draw not one an hour apart: my local NHS rounds up/ down TSH to for eg 0.03, Medichecks gives 0.029

[Zephyrbear in reply to Judithdalston]

Some of them around here can be a bit funny about it, so it’s easier to do it the way I do for me.

[Insomania]

I get different results on ferritin with TDL and nhs, I tend to do my tests on same day or week.

I consider the nhs one more accurate on ferritin because it’s venous draw by a blood nurse rather than me squeezing my finger.

[Jo5454 in reply to Insomania]

Yes I'm beginning to wonder about ferritin on pinprick tests? My NHS mid June was 37, I then had 3 fingerprick tests 3 consecutive wks, results were 85, 110, 65 & couplevwks layer, NHS one read 35. No signs of infection to cause the rise?

Now had another pinprick to try an iron profile. Ferritin was 85 which again I find hard to believe after barely taking iron, it takes many months normally. Another NHS one due in 3 wks, so will see!

Thyroid ones have on the whole given similar results in the past to NHS. Vit d, spot on.

[Pollypet]

Thank you - I often wondered whether or not there was much of a difference.

[LindyMc]

Interesting. The first time I used the private one I did n=1 test. It was done on the same day as the one from the surgery. In those day the surgery one was fasted for a full lipid panel and the private one is always fasted. The results were spot on.

[Buttercupsareyellow]

I found it interesting that in the summary you have posted the one unreliable one was glucose (which did not meet the criteria). This raises the question for me about diabetics who have to rely on finger prick blood testing to manage their glucose levels (and ergo insulin levels) which the medical profession universally seems to accept - whilst many medics are potentially wary of them being used for other monitoring…… interesting when they are always the ones that say we should go with the data….🤔

[Judithdalston in reply to Buttercupsareyellow]

Most insulin dependent diabetics in Uk use continuous glucose sensors now, which actually monitor not through blood but interstitial spaces, and now and again test they are being accurate with a traditional finger prick blood draw. They will not be the same figure , not recording the same thing in the same time, and for long term monitoring a venous blood draw gives the HbA1c. I’ m one of those diabetics who had done finger prick blood tests for decades but when it came to trying to fill a tiny phial had 10 digits punctured, lots of mess, and phial not filled up to line… never again!

[Buttercupsareyellow in reply to Judithdalston]

Sounds painful! I must admit I know very little about diabetic regimes. Every day is a school day - thank you for sharing, really informative and interesting to learn about 😊

[Judithdalston in reply to Buttercupsareyellow]

Lots of Big Pharma money in blood glucose testing so they make sure tests are accurate , even if like continuous glucose monitors aren’t even testing blood…they are rolling the technology out beyond type2 ( hardly touched in UK yet) to the healthy now in the US …same technology different marketing. No doubt will soon be here and adverts will appear making the healthy worried about their BG unnecessarily!

[tattybogle]

i tested using fingerprick (MMH ~nhs) and venous (GP)

same day , 45 minutes apart (both fasting)

GP ~ 11am.................... TSH 2.65 [0.57 - 3.6] ............. fT4 15.7 [7.9 - 14] ........128%

MMH ~ 11.45am........... TSH 2.9 [0.27 - 4.2] ............. fT4 22.1 [12 - 22] ........101%

it's hard to know what to make of that , as it's quite possible it 'really was' a little bit different since it was 45 mins later and i'd had a walk .... but i think it's likely that in this case the main difference is due to the different testing machines /ranges used , rather than the different method of drawing blood or transporting it.

Trying to compare results done with a narrow range those with a wider range is like comparing apples to pears.

[7.9-14] is a very narrow range of 6.1 so %'s will appear exaggerated in results that are over range when compared to %'s from a wider range (12-22 is a range of 10... nearly double ..)

[BB001 in reply to tattybogle]

Do they use the same Assay? This could explain the difference.

[tattybogle in reply to BB001]

they are different assay machines , you can tell by the very big difference in fT4 range .

7-14 is probaby a Beckman - Coulter platform,

don't know whose the 12-22 is,