Dr. Give: Help me understand anemia testing

[AnnE-girl]

Baby Boy had his twelve month checkup yesterday, which included testing for anemia since he is breastfed (and on solids now too, of course). The finger prick test was an 8.something, when it should have been an 11, so he had to have an arm blood draw to better know how much iron to supplement. The nurse called with the results this afternoon and he is fine after all. The more thorough test had his levels at 11.something, so within the range of normal. I understand that the small amount of blood for the finger prick serves as more of a screening, but I'm not clear on how the results could be so different. I was flustered on the phone because he had just gone down for a nap when the phone rang and I was half listening for him to wake up crying. The terms I'm using for my google search aren't coming up with any helpful explanations, so I thought I'd try the Hive. :-)

[hornblower]

They're probably looking at hemoglobin in the fingerstick. 

In a venous draw, they can look also at ferritin, hematocrit, serum iron etc. 

This little booklet from WIC explains those fingerstick machines & they give that result of 11+ as being the target  

Bottom line, sounds like he's fine & you needn't worry. Breastfeeding of course can safely continue for 2 years and beyond. :)

 

 

oops forgot the link http://itcaonline.com/wp-content/uploads/2011/10/Unit-3-Hemoglobin-Testing.pdf

 

Edited November 23, 2016 by hornblower

[AnnE-girl]

Thanks! I nurse my babies well into toddlerhood. Dd started negotiating that she would stop nursing if we had another baby when she was three and a half. She stopped on her own shortly after that. But, the doctor did mention that breastfed babies tend to be more susceptible to low iron since human milk doesn't have the large amounts of iron that formula has. She didn't say anything about the iron in my milk being more easily absorbed, but at least she didn't start pushing weaning when I said I nurse for years. :-)

[Lawana]

Did they have to squeeze his finger really hard to get the blood for the first test, or clean with alcohol and prick while still wet? It's possible for interstitial fluid or alcohol to dilute the blood, resulting in a lower reading, though that seems like a very large discrepancy to be be explained by either of those.

[AnnE-girl]

Did they have to squeeze his finger really hard to get the blood for the first test, or clean with alcohol and prick while still wet? It's possible for interstitial fluid or alcohol to dilute the blood, resulting in a lower reading, though that seems like a very large discrepancy to be be explained by either of those.

I'm not sure about the alcohol swab, but he was a good bleeder, so the nurse didn't really squeeze his finger.

[tm919]

There was a study done on this recently. The fingerprick thing is accurate when they average many drops (9?)... not so much if they did 1 or 2 drops. A lot of the low-cost screeners (this, the dried blood spot thing) have important limitations that vary from measurement to measurement.

Edited November 23, 2016 by tm919

[ktgrok]

I've had that happen...super super low on the finger prick (like...oh crap, you might need a transfusion type low) and then had it be significantly higher when doing an actual blood draw. The finger prick just isn't as accurate. No worries, mama!

[redheadmom]

As PP mentioned, they can look at much more with a larger sample from a blood draw vs a fewe drops. However, we had the opposite happen. At 12 months dd was a 14+ when they checked her iron level. I had to remind the pediatrician that I have to take iron supplements regularly. Apparently a lot of that passes through breastmilk.