Using z-scores to Interpret Pulmonary Function Test (PFT) Data

The 2022 European Respiratory Society/American Thoracic Society (ATS/ERS) PFT interpretation standards recommended that z-score be used to grade PFT results. This video will provide a concise definition of z-scores, and guidance on how z-scores are used to determine whether or not a measured PFT value should be categorized as normal or abnormal.

[@caileymiller3591]

Thank you!

[@maherahmed1977]

Thank you, well done!

[@pjsmdpete]

Thanks for the outstanding review. I am the medical director of a PFT lab in Baltimore. We are moving to z-scores (rather than percent predicted) in our interpretations for the reasons so elegantly discussed in your video. I am recommending this video to any of our staff that would like to delve more deeply into the basic statistical rationale for using z-scores in interpreting presence and severity of PFT abnormalities.

[@jeffreyhaynes2572]

Thank you Dr. Sloane, I'm pleased that so many are finding this video useful.

[@dr.swadeshmohanty1925]

Sir, kindly make videos on impulse oscillometry and CPET

[@drsakshi]

excellent

[@lancelothert]

Great video Jeff! Curious - When you went over the z-scores for spirometry, the abnormal values for FEV1 showed a z-score of -2.29 (mild), and a z-score for the FEV1/FVC ratio of -3.59 (moderate). Using the new recommendations, would you call this mild airflow obstruction based on the z-score for FEV1?

[@jeffreyhaynes2572]

Good question, obstruction on spirometry is defined by the FEV1/FVC ratio, so that's how I would quantify the level of obstruction. You can certainly have a normal FEV1 and a low FEV1/FVC, and you wouldn't classify such a spirometry result as normal.