I think you need to think about number needed to harm for each patient you see.
A number needed to harm of 2000 suggests that for every negative PECARN test on 2000 children with minor cHI not given a CT, 1 will have clinically significant ICH (not death or permanent disability - just admission or operation).
If you believe the increased risk of lifetime cancer increases 1:1000 per CT then of 2000 children scanned 2 will develop cancer. Ergo, you cause more harm harm than good.
(not to mention sedation risk, time in hospital catching disease, and what you could be doing better with the money spent on doing 1999 unnecessary CTs).
One of the problems of not using NNH or NNT type assessments is that we tend to overestimate prevalence of disease and are poor at calculating risk in our head.
The way your statement reads it suggests that your CT scan pick up rate of clinically important ICH in children with minor closed head injuries (that are PECARN negative) is more than than 3% (and up to 10%).
This does not sound likely and would not be consistent with the published evidence.
I think this young man should not have had a CT early in his presentation and given been advice to return for assessment if symptoms persist or worsen.
At the six week mark with these symptoms imaging is required but would be much more consistent with concussion and rarely late SDH.
I would have arranged an urgent MRI given the fact that he had no obviously clinical signs of impending dangerously raised ICP.
It is likely he has had this for many weeks and another day is unlikely to change things and if he clinically worsened a CT could be done then.
An MRI has the additional benefit of identifying subtle changes associated with concussion (whatever those are).
If I couldn't get access to MRI (probably with 2 days) then I would explain risk of CT to child and family and if they considered the risk of CT insignificant and they wanted it sooner then I would CT.
[my current risk statement is that a CT head is the same overall radiation as two trips from Australia to Europe and back, and younger children have higher risk]
PS Is anyone routinely using retinal venous pulsation examination in these children?
On 06/11/2012, at 9:24 AM, Jay Fisher wrote:
> Chris - Thank you for your thoughts but I respectfully disagree - I
> apologize in advance for the rant but I am just not an EBMer on this
> topic. It probably goes back to the fact that in the mid-80s I used to have
> to ask the *radiologist's *permission to get Head CTs on my head injured
> patients. Oy - gives me an ICH just thinking about it.
> Simply put, the calculation of the number needed to harm in a study
> population is not my concern when I am sitting in front of a patient
> deciding whether to image or not. I am concerned with having a false
> negative clinical assessment. I am concerned with harming 3-10% of patients
> with real injury by not obtaining the study.
> It really exemplifies how ridiculously confounded we are when trying to
> predict low frequency events. The PECARN study was awesome - but I
> personally don't think it was a rousing endorsement for the universal
> application of the instrument given the false negative rate.
> It doesn't minimize the importance of the research, and I do recognize that
> we should be parsimonious with radiation exposure. But the number of false
> negative clinical assessments in patients with the real disease is just too
> high for my liking.
> Jay Fisher
> Children's Hospital of Nevada
> On Mon, Nov 5, 2012 at 12:46 PM, Chris Pruitt, M.D <[log in to unmask]>wrote:
>> For the >2 year old group in the PECARN study, you're correct about the
>> sensitivity of the rule, but sensitivity is not the best approximation of
>> bedside utility (or harm) for a test (because of the low prevalence of
>> ciTBI, and how prevalence goes hand-in-hand with predictive values, etc.).
>> Number needed to harm is probably the most helpful way to think about it --
>> how many patients with no risk factors according to the rule would be
>> harmed if the rule were strictly applied? For their population, this was
>> approximately 2,000.
>> Chris Pruitt
>> From: Pediatric Emergency Medicine Discussion List [
>> [log in to unmask]] on behalf of Jay Fisher [[log in to unmask]]
>> Sent: Monday, November 05, 2012 9:13
>> To: [log in to unmask]
>> Subject: Re: Teenager with two days of headache
>> I am surprised by everyone's surprise.
>> We see patients with a normal neuro exam and positive head CTs with a low
>> but steady frequency.
>> We had a school age girl with just headache with a spontaneous ICH a few
>> years ago and a walking, talking teenager with an operable EDH just last
>> year. He had fallen off a bike with a brief LOC two days prior.
>> All the head injury/ CT research demonstrates that our standard decision
>> rules will miss ICH at a steady clip.
>> Even the PECARN data had a sensitivity of 96.8% for clinically important
>> ICH. That means one in thirty important injury gets missed. The confidence
>> interval (which is what you should really be looking at) went as low as
>> That means the best research ever on this topic says our decision rule,
>> within statistical confidence, could miss as many as 1 in 10 clinically
>> important ICH.
>> My experience is consistent with this.
>> Jay Fisher MD
>> Peds EM
>> Children's Hospital of NV
>> For more information, send mail to [log in to unmask] with the
>> message: info PED-EM-L
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Dr David Herd
Mater Children's Emergency
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