Assessment of smoking status in patients undergoing foot and ankle surgery

A. Swann, A. Goldberg, N. Cullen, D. Singh

Introduction: Wound healing and poor bone healing are complications seen in patients who smoke and some surgeons prefer not to operate on smokers. However, self reporting of smoking by patients may be biased. This study compares self-reporting of smoking habits and cotinine levels in the urine of our patients.

Method: 77 patients admitted for an osteotomy or arthrodesis procedure between September 2013 and May 2014 agreed to participate in this study. A questionnaire was completed and a urine sample was obtained and tested for cotinine, a metabolite of nicotine, by 2 techniques: a dipstick, the COT One Step Cotinine Test, yielding a positive result when the cotinine in the urine exceeds 200 ng/mL and the Concateno laboratory assay test, providing a mean value to give a qualitative reading whereby the cut off for non-smokers is 500ng/ml.

Results: Questionnaire results showed that 12 participants were active smokers, 35 classed themselves as ex-smokers and 30 were non-smokers. A dipstick result was negative in all the non-smokers, in 31/35 (89%) of the ex-smokers and in 4/12 (25%) of the current smokers. The dipstick test was positive in 4 self-reporting ex-smokers and only 8 of the 12 current smokers. The laboratory assay gave readings from 21 to 45,657 with higher readings being from heavier smokers. It correctly gave a value < 500 for all self-reporting non-smokers but 3 of the 35 self-reporting ex-smokers had a value between 500-5000ng/ml.

Conclusion: Whilst the majority of our patients had matching self-reporting smoking status and urine cotinine levels, 10% of self-reported ex-smokers had a high level of urine cotinine due to the test limitations or reporting bias by our patients. The £1.50 COT dipstick test is a cheap and easy way to correctly confirm a non-smoker compared to the Concateno laboratory assay which costs £7 excluding portering costs.