Just a Simple Blood Test

Kira and the stressed out mother.

This is a story about the unquantifiable cost of asking the doctor a question and then “just checking.”  The most interesting part about it to me has been the reaction I’ve received when recounting the story to mothers.  Almost all of them think I’m wrong.  I’ll give it to you and let you decide.

Kira is my 18 month old niece.  She lives in metro Detroit and is the 3rd child of my sister-in-law and her engineer husband.  Both parents are intelligent, college educated and, after 2 already, experienced.  Kira went for her 15 month well child check and was indeed totally “well.”  Unfortunately for Stephanie, her mother, she mentioned to the doctor that Kira didn’t seem to have much hair on the top of her head.  The doctor, whom I’m sure was busy as is per-usual, quickly ascertained that it was “probably nothing” but decided to “check some blood work.”  “Just to be sure.”

In medicine we discuss a thing called “pre-test probability.”  It helps us decide how much we should believe the results of a test.  For example, if we had a test to decide if I was male or female (we do) and we gave it to me what would we do if it came back saying I was female?  We wouldn’t believe it!  Since before we ordered the test we were 99.99999% sure I was male, the odds that the test is wrong are much higher than the odds I’m actually female.  Good doctors can actually put these numbers together – the pre test probability and the specificity of the test (more on specificity later) to decide if a test is even worth ordering.  The problem with ordering a test with less than perfect specificity is that a certain amount the time the test is going to come back “abnormal” and then the trouble begins.  You see there is NOTHING WRONG with the person; they just have an “abnormal” test which is NORMAL FOR THEM!

Let’s take an aside to discuss tests as it’s important to understand that an abnormal test does not, in and of itself, make a person abnormal.  Most tests, especially blood tests, have a range of “normal values.”  Usually if you test 100 people the results will end up all over with most of the people near the average.  Makes sense right?  If the average height of the average American male is about 5ft9 ½ in then a lot of men will be about 5ft 9in – 5ft 10 in but there will also be plenty at  5ft 7in and 6 ft.  So how short or how tall makes you “abnormal?”  Well fortunately for most types of things the results fall into what’s called a Gaussian curve. It looks like a bell.


(from Wikimedia Commons)

The vertical lines define what’s called a “standard deviation.”  In most tests we define “normal” as values that fall within 2 standard deviations of the “mean” (the average).  If you add up the numbers in the graph, counting 2 bars to the left and 2 bars to the right, you see that 95.6% of  “normal” people have a “normal” test result.  Well here’s the problem:  4.4% of NORMAL people have an ABNORMAL test result!  Throw in a few errors at the lab, a delay in processing, a squirming kid messing up the blood draw and you quickly see that over 1 in 20 tests on NORMAL people will have an ABNORMAL result!  If that doesn’t sound too bad remember that when we doctors draw blood, we rarely get only ONE test.  In fact, it’s often a lot easier to order a “SMA 23” which has TWENTY-THREE tests instead of the 1 or 2 you really needed.  That way we don’t “miss anything” and we often make a bit more money for it too.

Let’s go back for a moment to my average American male again.  Let’s say you walk into my office and you happen to be 6ft 7” tall.  Are you abnormal?  Well if I plot you out on a growth chart you are!


What should I do??  Check you for growth hormone excess?  Check you for Marfan’s syndrome?  Check for a few other exotic things that make people tall?  How about if I ask you some questions first?  “How tall is your father?”  “6ft 5 in.”  “Your mother?”  “6ft 1in”  “Any health problems?”  “No, they are both very healthy.”  Well now it doesn’t take a plasma physicist to figure out that you probably just inherited a few tall genes and ate well when you were growing up.  Although my “pre-test probability” is not 100% it’s pretty high.  If you are otherwise healthy should I do any tests “just to be sure?”

NO, NO, NO and NO AGAIN!!!!!

Unfortunately many, if not most, of the lay public doesn’t agree with me.  But since you are reading this book, I hope to educate you enough so that you can educate your doctor next time he tries to order a test.  You may be thinking “well what can it hurt?”  “Why not just be sure?”  Here’s why: you could get hurt, both mentally and physically.  It might also take a big dent out of your bank account.  I’ll get back to my niece Kira for now and later recall a few theoretical and a few real scenarios later to exemplify my point.

So as you have already guessed, Kira’s bloodwork came back with “an abnormality.”  This generated a phone call to my sister-in-law which immediately raised her anxiety level 2 notches from baseline (which was already high).  They did say “it’s probably nothing” but “we should check it again to make sure.”  Somehow that wasn’t too reassuring to Stephanie.  In addition, it generated another visit to the doctor.  More on this later (the doctor’s incentives) but suffice it to say he’s gonna make a little more money off the deal now.

Kira goes back to the doctor; she’s still healthy as a horse other than the normal colds she catches from her 2 brothers and the lack of hair.  Did I mention that by now the whole rest of the family has weighed in with the comment “but Stephanie you didn’t have any hair on the top of your head either when you were a baby!”  But now it’s too late.  No one can seem to stop the downhill run of the blood test locomotive.  We’ve got an “abnormal” result and everyone’s worried (at least a little bit) that it might be leukemia.  The doctor can’t stop it – he might be negligent, miss something, and get sued!  The parents aren’t going to NOT do what the doctor suggests at this point so they go back to the office.  A day off of work, hauling 3 healthy kids into a doctor’s office filled with a bunch of sick kids just to have 3 nurses hold the toddler down and let the doctor stick a needle in the kid to get another blood sample.  Please don’t misunderstand me here – I’m not saying she’s going to have long term emotional trauma from a simple blood test – I’m just saying it wasn’t necessary.

So, the results come back – you guessed it – still a “bit” abnormal.  Well now the doctor is actually pretty reassured.  It didn’t get significantly worse in one month so that makes it even more likely that it’s nothing serious.  Somehow that’s not incredibly reassuring to Stephanie.  Her baby still has an ABNORMAL BLOOD TEST.  “Ok” says the doctor.  “Try not to worry about it and we’ll check it one more time at her 18 month (2 months from now) well child check.  So they go home to worry for another 2 months.

2 months later:  Kira still doesn’t have a whole lot of hair but she’s otherwise completely healthy.  The doctor’s exam is normal, she’s growing, and they do blood work         AGAIN.Guess what? Still “abnormal” Just a tiny little bit “abnormal” but now they’re stuck.  They get a referral to a Pediatric Hematologist.  I’ll cut to the chase here and say the Specialist was great.  They looked the kid over, repeated the test one last time and proclaimed her “cured” (or, more appropriately never sick).  They offered her parents one more test in a month but specifically stated it wasn’t necessary.

So let’s review all the commotion the one blood test “just to be sure” caused.

1) Worry for a day about the test results

2) Worry more when the test results are abnormal – this time worry for a          whole month.

3) Lose a day of work to take the kid to the doctor AGAIN

4) Lose either the money or the vacation day by missing work

5) Watch your baby get strapped down and poked again while you stand        by helpless

6) Worry for another 2 days while the test is in the lab

7) Get a call from the nurse with the results – want to speak with the doctor – worry more

8) Get reassured by the doctor but don’t feel very reassured – worry for 2 more months

9) Take the kid AGAIN to the doctor, watch her get poked AGAIN and worry for another day

10) Get the results-get referred to the specialist- worry for 2 weeks                    awaiting appointment

11) Both parents miss a day of work, go to the Hospital, get blood drawn            AGAIN poked AGAIN and worry for another day.

12) FINALLY feel reassured enough to stop the insanity – exhausted and          much poorer

13) Baby is fine – but she was always fine!

Has something like this happened to you or your family?  Let me know I’m collecting stories.

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