Development of an indicator of smoking status for people with multiple sclerosis in administrative data

Background Administrative data lack health behavior information. Methods We developed an administrative case definition for past or current ('ever smoking') in 1320 individuals with MS from Manitoba, Canada. Candidate indicators for 'ever smoked' included smoking cessation medications, and diagnosis codes for tobacco use and chronic obstructive pulmonary disease, using variable lookback periods. Results When compared to self-reported smoking status, the case definition incorporating all indicators over a lifetime lookback period had a sensitivity of 31.98%, and positive predictive value of 78.26%. Conclusion This smoking status definition could only partially control for confounding due to smoking because of the low sensitivity.