Total pack year calculation

[DrMuir]

Recommend caution in total pack year calculation based upon last observation since a typical person who smoked 1 pk/day for 10 years from age 20 then 2 pk/day for 10 years then 1 pk/day for 5 years then stopped 5 years ago (or 16 years ago) but currently nonsmoker would have hit a total of 35 pk years at age 61 but if based upon most recent calculation would be incorrect.
Clinicians usually capture current ppd but determine total risk as a ballpark score calculated from each range.
Thank you. PMuir MD