Skip to main content Accessibility help

Analysis of Agreement between Expired-Air Carbon Monoxide Monitors

  • Joshua L. Karelitz (a1), Valerie C. Michael (a1) and Kenneth A. Perkins (a1)


Introduction: The current study examined the level of agreement in expired-air carbon monoxide (CO) values, focusing especially on those confirming abstinence, between the two most commonly used CO monitors, the Vitalograph BreathCO and the Bedfont piCO+ Smokerlyzer.

Methods: Expired-air samples were collected via both monitors from adult dependent smokers (44 M, 34 F) participating in studies using CO values to confirm abstinence durations of: 24 hours, 12 hours, or no abstinence. All met DSM-IV nicotine dependence criteria and had a mean (SD) Fagerström Test of Cigarette Dependence score of 5.1 (1.8). Paired data collected across multiple visits were analyzed by regression-based Bland–Altman method of Limits of Agreement (LoA).

Findings: Analysis indicated a lack of agreement in CO measurement between monitors. Overall, the Bedfont monitor gave mean (±SEM) readings 3.83 (±0.23) ppm higher than the Vitalograph monitor. Mean differences between monitors were larger for those ad lib smoking (5.65 ± 0.38 ppm) than those abstaining 12–24 hours (1.71 ± 0.13 ppm). Yet, there also was not consistent agreement in classification of 24-hour abstinence between monitors.

Conclusions: Systematic differences in CO readings demonstrate these two very common monitors may not result in interchangeable values, and reported outcomes in smoking research based on CO values may depend on the monitor used.


Corresponding author

Address for correspondence: Joshua. L. Karelitz, University of Pittsburgh School of Medicine, 3811 O’Hara Street, Pittsburgh, PA 15213. Email:


Hide All
Addicott, M. A., Baranger, D. A., Kozink, R. V., Smoski, M. J., Dichter, G. S., & McClernon, F. J. (2012). Smoking withdrawal is associated with increases in brain activation during decision making and reward anticipation: A preliminary study. Psychopharmacology, 219 (2), 563573. doi:10.1007/s00213-011-2404-3.
Altman, D. G. (1993). Construction of age-related reference centiles using absolute residuals. Statistics in Medicine, 12 (10), 917924. doi:10.1002/sim.4780121003.
American Psychiatric Association (1994). Diagnostic and statistical manual of mental disorders (4th ed.). Washington, DC: Author.
Benowitz, N. L., Jacob, P., Hall, S., Tsoh, J., Ahijevych, K., & Jarvis, M. J. et al. (2002). Biochemical verification of tobacco use and cessation. Nicotine and Tobacco Research, 4 (2), 149159. doi:10.1080/14622200210123581.
Bland, J. M., & Altman, D. (1986). Statistical methods for assessing agreement between two methods of clinical measurement. The Lancet, 327 (8476), 307310. doi:10.1016/S0140-6736(86)90837-8.
Bland, J. M., & Altman, D. G. (1995). Comparing methods of measurement: Why plotting difference against standard method is misleading. The Lancet, 346 (8982), 10851087. doi:10.1016/S0140-6736(95)91748-9.
Bland, J. M., & Altman, D. G. (1999). Measuring agreement in method comparison studies. Statistical Methods in Medical Research, 8 (2), 135160. doi:10.1177/096228029900800204.
Bland, J. M., & Altman, D. G. (2003). Applying the right statistics: Analyses of measurement studies. Ultrasound in Obstetrics and Gynecology, 22 (1), 8593. doi:10.1002/uog.122.
Brown, R., & Richmond, S. (2005). An update on the analysis of agreement for orthodontic indices. The European Journal of Orthodontics, 27 (3), 286291. doi:10.1093/ejo/cjh078.
CoVita (2010). piCO+ Smokerlyzer operating manual. Retrieved from
Cropsey, K. L., Trent, L. R., Clark, C. B., Stevens, E. N., Lahti, A. C., & Hendricks, P. S. (2014). How low should you go? Determining the optimal cutoff for exhaled carbon monoxide to confirm smoking abstinence when using cotinine as reference. Nicotine & Tobacco Research, 16 (10), 13481355. doi:10.1093/ntr/ntu085.
Dallery, J., & Raiff, B. R. (2007). Delay discounting predicts cigarette smoking in a laboratory model of abstinence reinforcement. Psychopharmacology, 190 (4), 485496. doi:10.1007/s00213-006-0627-5.
Emery, R. L., & Levine, M. D. (2015). Optimal carbon monoxide criteria to confirm smoking status among postpartum women. Nicotine & Tobacco Research. Advance online publication. doi:10.1093/ntr/ntv196.
Erb, P., Raiff, B. R., Meredith, S. E., & Dallery, J. (2015). The accuracy of a lower-cost breath carbon monoxide meter in distinguishing smokers from non-smokers. Journal of Smoking Cessation, 10 (01), 5964. doi:10.1017/jsc.2013.37.
European Respiratory Society (n.d.). Exhaled CO measurement. Retrieved January 6, 2015, from
Fagerström, K. (2012). Determinants of tobacco use and renaming the FTND to the Fagerström test for cigarette dependence. Nicotine and Tobacco Research, 14 (1), 7578. doi:10.1093/ntr/ntr137.
Froeliger, B., Modlin, L., Wang, L., Kozink, R. V., & McClernon, F. J. (2012). Nicotine withdrawal modulates frontal brain function during an affective Stroop task. Psychopharmacology, 220 (4), 707718. doi:10.1007/s00213-011-2522-y.
Hanneman, S. K. (2008). Design, analysis and interpretation of method-comparison studies. AACN Advanced Critical Care, 19 (2), 223. doi:10.1097/01.AACN.0000318125.41512.a3.
Heatherton, T. F., Kozlowski, L. T., Frecker, R. C., & Fagerström, K. O. (1991). The Fagerström test for nicotine dependence: A revision of the Fagerström tolerance questionnaire. British Journal of Addiction, 86 (9), 11191127. doi:10.1111/j.1360-0443.1991.tb01879.x.
Jarvis, M. J., Belcher, M., Vesey, C., & Hutchison, D. C. (1986). Low cost carbon monoxide monitors in smoking assessment. Thorax, 41 (11), 886.
Javors, M. A., Hatch, J. P., & Lamb, R. J. (2005). Cut-off levels for breath carbon monoxide as a marker for cigarette smoking. Addiction, 100 (2), 159167. doi:10.1111/j.1360-0443.2004.00957.x.
Lamb, R. J., Morral, A. R., Galbicka, G., Kirby, K. C., & Iguchi, M. Y. (2005). Shaping reduced smoking in smokers without cessation plans. Experimental and Clinical Psychopharmacology, 13 (2), 83. doi:10.1037/1064-1297.13.2.83.
Ludbrook, J. (2002). Statistical techniques for comparing measurers and methods of measurement: A critical review. Clinical and Experimental Pharmacology and Physiology, 29 (7), 527536. doi:10.1046/j.1440-1681.2002.03686.x.
Mantha, S., Roizen, M. F., Fleisher, L. A., Thisted, R., & Foss, J. (2000). Comparing methods of clinical measurement: Reporting standards for Bland and Altman analysis. Anesthesia & Analgesia, 90 (3), 593602. doi:10.1097/00000539-200003000-00018.
McNeill, A. D., Owen, L. A., Belcher, M., Sutherland, G., & Fleming, S. (1990). Abstinence from smoking and expired-air carbon monoxide levels: Lactose intolerance as a possible source of error. American Journal of Public Health, 80 (9), 11141115. doi:10.2105/AJPH.80.9.1114.
Middleton, E. T., & Morice, A. H. (2000). Breath carbon monoxide as an indication of smoking habit. CHEST Journal, 117 (3), 758763. doi:10.1378/chest.117.3.758.
Morimatsu, H., Takahashi, T., Matsusaki, T., Hayashi, M., Matsumi, J., & Shimizu, H. et al. (2010). An increase in exhaled CO concentration in systemic inflammation/sepsis. Journal of Breath Research, 4 (4), 047103. doi:10.1088/1752-7155/4/4/047103.
Moscato, U., Poscia, A., Gargaruti, R., Capelli, G., & Cavaliere, F. (2014). Normal values of exhaled carbon monoxide in healthy subjects: Comparison between two methods of assessment. BMC Pulmonary Medicine, 14 (1), 204. doi:10.1186/1471-2466-14-204.
Perkins, K. A., Jao, N. C., & Karelitz, J. L. (2013a). Consistency of daily cigarette smoking amount in dependent adults. Psychology of Addictive Behaviors, 27 (3), 723. doi:10.1037/a0030287.
Perkins, K. A., Karelitz, J. L., Conklin, C. A., Sayette, M. A., & Giedgowd, G. E. (2010). Acute negative affect relief from smoking depends on the affect situation and measure but not on nicotine. Biological Psychiatry, 67 (8), 707714. doi:10.1016/j.biopsych.2009.12.017.
Perkins, K. A., Karelitz, J. L., & Jao, N. C. (2013b). Optimal carbon monoxide criteria to confirm 24-hr smoking abstinence. Nicotine and Tobacco Research, 15 (5), 978982. doi:10.1093/ntr/nts205.
Perkins, K. A., Karelitz, J. L., & Michael, V. C. (2015). Reinforcement enhancing effects of acute nicotine via electronic cigarettes. Drug and Alcohol Dependence, 153, 104108. doi:10.1016/j.drugalcdep.2015.05.041.
Perkins, K. A., Karelitz, J. L., Michael, V. C., Fromuth, M., Conklin, C. A., & Chengappa, K.R. et al. (2016). Initial evaluation of fenofibrate for efficacy in aiding smoking abstinence. Nicotine & Tobacco Research. 18 (1), 7478. doi:10.1093/ntr/ntv085.
Raiff, B. R., Faix, C., Turturici, M., & Dallery, J. (2010). Breath carbon monoxide output is affected by speed of emptying the lungs: Implications for laboratory and smoking cessation research. Nicotine and Tobacco Research, 12 (8), 834838. doi:10.1093/ntr/ntq090.
VanderVeen, J. W., Cohen, L. M., Cukrowicz, K. C., & Trotter, D. R. (2008). The role of impulsivity on smoking maintenance. Nicotine & Tobacco Research, 10 (8), 13971404.
Vitalograph (n.d.). Vitalograph BreathCO quick start user training manual. Retrieved from
West, R. J. (1984). The effect of duration of breath-holding on expired air carbon monoxide concentration in cigarette smokers. Addictive Behaviors, 9 (3), 307309. doi:10.1016/0306-4603(84)90026-1.


Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed