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Mitoses per HPF Unit of measurement

(Dmytry Dymshyts) #1

Ingesting NAACCR to OMOP vocabulary,

I’ve noticed such a values:
“Mitotic count (per 10 HPF) greater than 20”
“0.9 mitosis per 10 HPF”
“0.9 mitosis per 40 HPF”
“11 or more mitoses per 50 HPF”
and others

We want to parse them as a combination of operator_concept_id, unit_concept_id and numeric_value itself.
So, I have doubts about units I can use in this case.
We have these source_units of measurement:
“mitoses per 10 HPF”
“mitoses per 40 HPF”
“mitoses per 50 HPF”

It’s pretty important to know mitoses number in those cancer specimen.
Pathologists have standardized techniques looking at 10, 40 or 50 high power fields to evaluate this.

We have UCUM concept with concept_name =‘per high power field’.
On the one hand ‘mitoses per 50 HPF’ value is equal to ‘per high power field’ value / 50,
on the other hand since “50” is more the way the evaluation was performed, then a denominator, I would create new concept for each of
“mitoses per 10 HPF”
“mitoses per 40 HPF”
“mitoses per 50 HPF”

Are you guys agree with that?
@Christian_Reich @rimma @mgurley

(Jeremy Warner) #2

Hi Dima,

These and similar “per HPF” type of data come from value sets which are typically created and updated by the College of American Pathologists’ Cancer Committee. Since not all HPF are created equal (40x and 100x and 150x are all high-powered fields, for example), they are inherently not truly a numeric measurement. I’m not sure if Rich Moldwin is on the OHDSI forum but he would be the one to chat with to learn more about the value sets, some of which might actually already be represented in SNOMED-CT.

(Christian Reich) #3


Yeah, it’s a little ugly. In principle, the mitotic rate is supposed to be normalized to square millimeter, but many pathologists still use HPFs and choose a different magnifications to get a good number of mitoses into the eyepiece. Since we haven’t started the conversion of units yet, we should support the HPFs. I think just @Dymshyts said.

No, we don’t have Rich signed up to the OHDSI Forum. Want to invite him, @Jeremy_Warner?

(Dmytry Dymshyts) #4

I though about this before posting the initial post but got totally confused.
I found that 1 HPF = 0.785 mm2
And there are not so many sources in the internet saying this.
On the other hand, in NAACCR data we have these:
“Stated as less than 1 mitosis per 50 HPF (40x fields)” =>Has synonym=> “Stated as less than 1 mitosis per 5 square mm”
“51 or more mitoses per 10 HPF (40x field)” =>Has synonym=> “51 or more mitoses per 2 square mm”
Means, 50 HPF = 5 mm3, while 10 HPF = 2 mm3 (not 1, which is weird).

(Christian Reich) #5

@Dymshyts: No over-engineering necessary. We are not converting kg, inches and stones, either. Or mg/dL to mmol/L. Or any of that. Not yet. We will. So, if they have a number of mitoses in 50xHPF - so be it. you provided the solution already.