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Secondary PAH mapped to secondary PH, but not to PAH


I recently observed a shortcoming in the vocabulary hierarchy for Pulmonary Hypertension (PH). PH can be classified according to its underlying causes as follows (with ICD codes):

A. Pulmonary Arterial Hypertension (PAH): primary/idiopathic/heritable PAH (I27.0); secondary/associated forms of PAH (I27.21)
B. (other) secondary PH: PH due to left heart disease (I27.22); PH due to lung disease and/or hypoxemia (I27.23); Chronic Thromboembolic PH (I27.24); PH with unclear and/or multifactorial mechanisms (I27.28, I27.29)

It seems that I27.21 got mapped to an ancestor of Secondary PH (SNOMED Concept ID 4339214), but not to an ancestor of PAH (SNOMED Concept ID 4013643), which would be much more intuitive and correct. We missed quite a lot of PAH patients in a recent feasibility assessment – and stopped the study – because of that.

Is there a chance to update the vocabulary/vocabulary hierarchy to address the problem? This would be fantastic.

Thanks & all the best,


Hello, thank you for pointing this out! This part of hierarchy indeed seems weird. The issue will be fixed.

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Thank you, Tatiana!

Hello Eva,
writing to inform you that Secondary pulmonary hypertension, I27.21 is now a child of Pulmonary arterial hypertension. Hope this helps you in your work!

We are pleased to inform you that the issue has been successfully corrected during the February 2024 Release. Thank you very much for your contribution!