Gone fishin … Why I don’t cast a wide net when ordering lab tests

“How do you know what blood tests to order for your patients?”

“Why don’t kids get many blood tests?”

“What screening blood tests DO kids get?”

A very #smartmomma asked me these questions recently, and I think they are good ones: so good that I became inspired to write my blog entry well before the 11^th hour (most unusual). More importantly, it has enabled me to pause and reflect upon an aspect of pediatric clinical practice that is part-uniformly standard and part-individual practitioner dependent.

I’m happy to report that as a general rule the large majority of children do NOT need blood tests.

Most kids are healthy, and so there’s really no need to send many blood tests JUST BECAUSE.  As a specialty, we do screen children for a few diseases as a uniform standard—we check a blood sample in the newborn period for some genetic diseases like PKU (phenylketonuria -25 cents-) and sickle cell disease, and at age 4 we check the blood for the hemoglobin level, which tells us if a patient is anemic (low blood) or not.

For children who live in very old houses that may have lead paint, it’s important to check a blood lead level between 12 and 24 months.  Thankfully though, homes that contain lead paint aren’t ALL that common anymore, so screening the home history first gives us a clue as to whether that blood test should be sent (although many pediatricians will send a lead level on everyone). Some children with family history of high cholesterol will get a fasting lipid profile somewhere between ages 9 and 11, but that’s pretty much it.  The tests that are sent are ones for which early intervention is possible and important.

Notice that there’s no mention in the paragraph above of checking electrolytes or white cell count or kidney or liver function or other random blood tests. Those tests should only be ordered if there’s a SPECIFIC need, and furthermore, if the results of those tests would indicate a certain and specific direction for treatment.  In other words, there’s no need to just go “fishing” for test results.  Lab studies of any kind really should be sent in order to answer a specific question and provide a distinct guide towards a care plan.

Every now and then a few of my patients’ parents will say: “well aren’t you going to send any tests?”

A great question for sure, and here’s where I think it’s important to understand this concept of only sending tests that are warranted, and whose results would direct the clinician towards or away from a certain treatment.  Casting a wide net of blood tests isn’t good medicine or smart resource management. And and I’m not even getting into the discussion of a painful needle stick for a child or the difficulty in actually obtaining a sample from those tiny veins!  In my practice I try to be cognizant of the rationale for which I send every test and I ask myself the following questions:

1. Is it necessary?
2. Is it feasible/possible?
3. Will my treatment change because of the result?

Here’s an example of my individual thought process as a clinician.

If a child comes to see me with a fever and an infection in the skin that is red and looks like a typical cellulitis, I’m not going to send a blood test to check the white blood cell count, which is typically elevated in the setting of infection.  Knowing what that number is will not affect my treatment of the child nor change my practice in any way, so why would I subject the child to a needlestick? Why would I subject the “system” to the cost of utilizing the human resources required to get the test, plus the cost to analyze it in the lab? Would it be NICE to know what that white blood count is?  Sure.  I’m interested.  But do I NEED to know what it is in this situation?  I don’t. So in the words of Yoda: send it I shall not.

I gave a lecture a few weeks ago to a group of doctors,

many of them from “the old guard” and much older than me, and none of them pediatric trained.When I spoke about a case of a child with a fever for whom casting that wide net of bloodwork didn’t happen, one physician was surprised and clearly uncomfortable that I had performed my medical decision-making without the aid of blood tests.  He was much more used to a medical practice climate where the critical appraisal of test ordering was much less of a “thing,” and it was in that moment that I realized how much medicine has changed in this regard.  I will say, however, that most pediatricians are fairly “minimalist” on the intervention spectrum. But every clinician is slightly different indeed.

I was and am honestly thankful to be in pediatrics, where I’m not bogged down by chasing lab values constantly.  I never want to get stuck treating “numbers.” Blood tests should be an adjunct to clinical practice, not the primary driver.  There are individual clinical scenarios where a large battery of tests are warranted, but as I reflect upon my term of clinical practice, those cases are relatively few and far between.

And so – my cellulitis patient mentioned above?

Got better with antibiotics and without a blood test.  The child with fever?  Same deal, but no antibiotics given.  I hope my friend who originally asked these blood test questions will be satisfied with my responses. I need to thank her, because she’s renewed my commitment to make sure that every test I order will have a rationale behind it.  I hope that a few people who have also asked: “are you going to order any tests?” will have read this too, and now they feel better able to process the answer if it happens to be –

“NO.”

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