The accuracy of urinary cotinine immunoassay test strip as an add-on test to self-reported smoking before major elective surgery.

ABSTRACT

INTRODUCTION: Smoking is a preventable cause of perioperative complications. An accurate and rapid classification of smoking status is essential as up to 35% of smokers deny smoking before surgery. We compared the diagnostic performance of a preoperative urinary cotinine immunoassay test strip (NicAlert®) as an add-on test to patient's self-reported smoking status. METHODS: Four hundred and sixty-five patients undergoing major elective surgery self-reported their smoking history and provided a sample for measuring urinary cotinine concentration by liquid chromatography tandem mass spectrometry (reference standard) and NicAlert®. Using the "either test positive" rule, the gain in diagnostic performance for NicAlert® add-on test was assessed using relative positive and negative likelihood ratios (LRs) and area under the receiver operating characteristic curve (AUROC) with 95% CIs. RESULTS: Of the 60 patients with a positive reference standard (adjusted cotinine ≥ 50 ng/ml), 10 (16.7%) denied current cigarette smoking. The NicAlert® add-on test had better test performance measures (sensitivity = 95.0%, specificity = 94.8%) than self-reported smoking history alone (sensitivity = 83.3%, specificity = 95.0%). The relative positive and negative LRs were 1.09 (95% CI = 0.95-1.24) and 0.30 (95% CI = 0.12-0.78), respectively. The AUROC for the NicAlert® add-on test (0.90; 95% CI = 0.84-0.96) was significantly higher than for the self-reported smoking history alone (0.78; 95% CI = 0.69-0.88) (p = .006). CONCLUSION: The NicAlert® add-on test strategy had excellent diagnostic test performance for identifying current smokers who are expected to have a high risk of perioperative complications.