Agreement between exhaled breath carbon monoxide threshold levels and self-reported cigarette smoking in a sample of male adolescents in Jordan

Evaluating the impact of varying expired carbon monoxide thresholds on smoking relapse identification: insights from the E3 trial on e-cigarette efficacy for smoking cessation

OBJECTIVES

Expired carbon monoxide (ECO) is often used in smoking cessation trials to biochemically validate self-reported smoking status. The optimal ECO threshold to distinguish individuals who smoke from those who do not is debated.

DESIGN

The data from the 'Evaluating the Efficacy of E-Cigarette use for Smoking Cessation (E3) Trial' were used; the E3 trial was a randomised controlled trial that examined e-cigarettes efficacy for smoking cessation.

SETTINGS

Participants were recruited from 17 Canadian sites across 4 provinces.

PARTICIPANTS

This substudy included data from participants who returned for at least one of the clinical visits at week 4 (291), 12 (257) or 24 (218) and provided both self-reported smoking status and ECO measures. Analyses were based on 766 paired measures (ie, self-reported smoking status with corresponding ECO).

RESULTS

The ability of ECO measurements to discriminate between adults who reported smoking and those who reported abstinence varied with the threshold used. ECO thresholds of 6, 7, 8 and 9 parts per million (ppm) yielded the greatest area under the receiver operating characteristic curve (0.84). These thresholds produced sensitivities of 84%, 82%, 78% and 76% and specificities of 84%, 87%, 90% and 91%, respectively. However, at a threshold of 6 ppm, intersecting sensitivity (84%) and specificity (84%) were maximised with respect to each other. Biochemical validation had the highest agreement with self-report at an ECO threshold of 6 ppm (κ=0.57; 95% CI, 0.51 to 0.64).

CONCLUSION

The classification of participants' smoking status depends on the ECO threshold used for biochemical validation. We recommend that future smoking cessation trial investigators analyse and report the impact that varying ECO thresholds has on trial results.

TRIAL REGISTRATION NUMBER

NCT02417467.

Examining the effect of exercise on the relationship between affect and cravings among smokers engaged in cessation treatment

Cigarette smoking is associated with multiple adverse health outcomes. When smokers attempt to quit smoking, one of the leading predictors of relapse are cravings. Recent research shows a relationship between positive and negative affect, exercise, and cravings, but the exact nature of this relationship has yet to be understood. This study explored the relationships between positive and negative affect and cravings in a sample of participants with elevated levels of depressive symptoms (N = 202; 68.8% female; mean age = 46.1 years) who were enrolled in a smoking cessation trial to test the efficacy of a 12-week exercise intervention relative to a health education control on smoking outcomes. Data on affect and craving were gathered before weekly study intervention sessions, and data on cravings were gathered again after each session. The results showed that negative affect had a significant and positive association with cravings before an exercise or health education session. After the session, positive and negative affect were not significant predictors of changes in cravings from pre-session. However, regardless of level of positive or negative affect participants in the exercise condition showed greater reductions in craving pre- to post-class than those in the control condition. These findings suggest that negative affect is associated with cravings, but cravings can be mitigated by exercise.

Ga-68 EDTA aerosols in evaluation of inhaled-particle deposition and clearance of obstructive pulmonary diseases: A pilot prospective study compared with Galligas

PURPOSE

68-gallium (Ga-68) ethylenediaminetetraacetic acid (EDTA) aerosols and Galligas were compared in evaluation of inhaled-particle deposition and clearance in volunteers with or without obstructive pulmonary diseases.

METHODS

Nonsmoking healthy volunteers, healthy smokers, asthma patients and patients with chronic obstructive pulmonary disease (COPD) were recruited to undergo the dynamic lung ventilation positron emission tomography/computerized tomography (PET/CT) scans within two consecutive days. The inhaled particles were Ga-68-labelled carbon nanoparticles (Galligas, 30-60 nm in size) and Ga-68-labelled EDTA aerosols (1-2 μm in size), respectively. The volunteers' lung function parameters were measured for comparison.

RESULTS

Central deposition and inhomogeneity of both tracers were negatively correlated with lung function parameters, including the ratio of forced expiratory volume at 1 second to forced vital capacity (FEV₁ /FVC). The central or hilum deposition of Galligas, but not 68-gallium (Ga-68) EDTA, was negatively correlated with the maximal expiratory flow at 25%, 50% and 75% of the forced vital capacity. Compared with Galligas, Ga-68 EDTA aerosols were more concentrated in the central region in all groups except for the healthy nonsmokers. Ventilation inhomogeneity was more evident when using Ga-68 EDTA aerosols, especially in patients with COPD and asthma patients. In the healthy smokers, the central region accumulated more Ga-68 EDTA at 30 minutes after inhalation than immediately after inhalation. Ga-68 EDTA cleared faster in lungs than Galligas.

CONCLUSIONS

Both Galligas and Ga-68 EDTA aerosols can be used for PET/CT lung ventilation scan. However, Ga-68 EDTA aerosols showed more advantages in diagnosis and evaluation of obstructive airway diseases by revealing the inhaled-particle deposition and clearance.

Can Exhaled Carbon Monoxide Be Used as a Marker of Exposure? A Cross-Sectional Study in Young Adults

Carbon monoxide (CO) poisoning is a major public health issue worldwide. People are exposed to CO in their daily lives, with one of the common sources of CO being cigarette smoking. Inhalation of CO leads to elevated carboxyhaemoglobin (COHb) levels in the blood and also in exhaled CO concentration. Several factors have been shown to affect COHb concentration and COHb half-life. However, factors affecting exhaled CO concentration and exhaled CO half-life are not well understood. The present study aimed to investigate the potential factors related to baseline exhaled CO concentration and exhaled CO half-life among smokers. A cross-sectional study was conducted between 26 January and 30 June 2019, and young adults were recruited into the study. A total of 74 participants (mean age: 27.1 years, 71.6% males and 28.4% females) attended the study. They were invited to complete a questionnaire, including demographic, physiological, and behavioural factors. Then, exhaled CO measurements were taken. These measurements were taken before and after smoking a single cigarette for smokers and only once for non-smokers. The average baseline exhaled CO concentration was 6.9 ± 4.9 ppm for smokers and 1.9 ± 0.5 ppm for non-smokers. The mean of exhaled CO half-life was around 273.3 min (4.6 h) for smokers. No difference was seen in exhaled CO half-life between light smokers and heavy smokers in the smoking group. Gender and cigarettes smoked weekly affected baseline exhaled CO in smokers. Even though height seemed to positively associate with exhaled CO half-life, the relationship disappeared when adjusting by gender and weight. Therefore, exhaled CO could be used as a marker of CO exposure, but we cannot ignore the factors mentioned in the study. For future study, considering factors related to smoking habits and smoking style are recommended as these may affect total inhaled CO.

Breath analysis using a spirometer and volatile organic compound sensor on driving simulator

In this study the correlation between the condition of drivers and their expiration was evaluated by analyzing the exhalation of car drivers in a simulation setting using a spirometer and a volatile organic compound (VOC) gas sensor. Participants wore exhalation masks and their expiration was monitored for fluctuations in breath measurements, including VOC concentration, oxygen intake, carbon dioxide excretion, and respiration rate. Participants used a driving simulator on four different courses of varying difficulty for approximately five min each, with the mean and standard deviation (SD) being calculated for each parameter during the cruising section of the course. After driving each course, participants assessed the 'enjoyment' and 'difficulty' of their experience. It was verified whether the state of the participants during driving can be determined from exhalation by comparing the questionnaire results. The mean and SD of all exhalation parameters were analyzed using box-and-whisker plots and any statistical significance between these parameters and driver experience was tested using the analysis of variance. There was no significant difference in the correlation between the questionnaire result of 'difficulty' and each exhalation parameter. By contrast, the low assessment group of 'enjoyment' showed large SDs in all parameters from both the VOC gas sensor and spirometer.

The Effect of a "Class Smoke Free Pledge" on Breath Carbon Monoxide in Arabic Male Adolescents

Introduction

Arabic male adolescents have a high smoking prevalence. Introduction of "Class smoke-free" pledges have been successful amongst European adolescents but have not been evaluated using objective valid measures. We tested the impact of adding a smoke free pledge strategy to a proven peer-led asthma and smoking prevention program on breath carbon monoxide level (BCO) in male high-school students in Jordan.

Methods

We enrolled male students from four high-schools in Irbid, Jordan. Schools were randomly assigned to receive either TAJ (Triple A in Jordan, n = 218) or TAJ-Plus (with added class smoke-free pledge, n = 215). We hypothesized that students receiving TAJ-Plus would have greater reduction in BCO levels than those only receiving the TAJ intervention. Asthma and smoking status were assessed by self-administered questionnaires. Smoking outcomes were collected using a BCO Monitor.

Results

Both groups had significant reductions in BCO levels post-intervention (p < .0001), however, decreases were greater in TAJ-Plus group (3.9 ± 0.2 vs. 4.8 ± 0.2, p < .0001). Intervention effects on BCO over time did not vary by smoking status (p = .085), asthma status (p = .602), or a combination of the two (p = .702).

Conclusions

An added smoke-free pledge strategy to a proven peer-led asthma education program appears to be a promising approach to motivate adolescents to abstain from smoking in Jordan. Future research is required to determine if these results can be extended to Jordanian adolescent females.

Implications

A commitment by students via a "class smoke-free" pledge can be an added incentive to motivate adolescents in Arabic-speaking countries to abstain from smoking. Social influence approaches in schools can be useful in countering the aggressive tobacco marketing campaigns targeting Jordanian and other Arabic-speaking youth. The combination of "class smoke-free" pledges and an evidence-based peer-led asthma and smoking education can be implemented in schools to influence adolescents with asthma to abstain from smoking.

Factors associated with different smoking statuses among Malaysian adolescent smokers: a cross-sectional study

BACKGROUND

This study focused on the associations between socioeconomic status (SES) and adolescent smoking among secondary school students (13 to 17 years) in the Federal Territory of Kuala Lumpur, Malaysia. Our objective was to evaluate the relationships between adolescent demographics, socioeconomic status and smoking status.

METHODS

The survey data were based on baseline findings from a cross-sectional study (N = 422 adolescents). Chi-square test was used to assess the relationship between demographic characteristics, socioeconomic status (household monthly income and daily allowance) and adolescent smoking status. Exhaled carbon monoxide (CO) reading and the Hooked on Nicotine Checklist (HONC) were used to evaluate adolescent smoking status. A Multivariate Multinomial Logistic Regression (MMLR) was employed to test selected demographic and socioeconomic predictors of smoking status.

RESULTS

Of the 422 adolescents (M age = 15.58, SD = 1.24), more than half of the participants initiated smoking between 13 to 17 years old (59.0%). A total of 308 (73.0%) were electronic cigarette users, with more than 50% comprising of single users. The mean CO reading was 2.14 ppm with 78.0% of adolescents scoring more than 0 on the Hooked on Nicotine Checklist (HONC). Males and participants aged 15 and 16 years were at increased risks of sole CC smoking. Meanwhile, males, those who are not hooked on smoking and with a non-smoker CO reading were at increased risks of sole EC smoking. Finally, Bumiputeras were at less risk of EC smoking.

CONCLUSIONS

Demographic variables such as age, gender and ethnicity predicted smoking status predicted smoking risk, but not socioeconomic factors. The findings allow policy makers to target specific high-risk demographic groups when designing smoking cessation programs for adolescents.

Air pollution may affect the assessment of smoking habits by exhaled carbon monoxide measurements

BACKGROUND

While European air quality policies reduce ambient carbon monoxide (CO) concentrations in general, there are still areas affected by high environmental CO exposure from transportation, industry and burning low-quality fossil fuels. We investigated, how these CO amounts might influence exhaled CO measurements used to monitor the smoking status of healthy subjects.

METHODS

A cross-sectional study of healthy adults living in areas of high air pollution (N = 742) and low air pollution (N = 197) in Poland. They completed a survey regarding their smoking habits and underwent necessary body measurements including exhaled CO concentration levels.

RESULTS

Ambient CO levels were much higher in highly pollutes cities. Also exhaled CO levels in subjects from high pollution areas were significantly higher, independent of subject smoking status (8.25 ppm vs. 3.26 ppm). Smokers exhaled more CO than non-smokers. Although the duration of smoking did not affect the CO levels, they were proportional to the number of cigarettes smoked during the day, especially for higher amounts of cigarettes and in unpolluted areas. It was possible to differentiate active from passive smokers in all areas, but the difference for passive smokers vs. non-smokers was significant only in low pollution city inhabitants.

CONCLUSIONS

Exhaled CO levels were confirmed to be a good indicator of smoking status and smoking pattern in healthy subjects. However, high environmental CO levels both increase baseline exhaled CO concentrations in non-smokers affecting their discrimination from passive smokers, and obscure categorizing cigarette consumption in heavy smokers. These findings add important evidence on both understanding of exhaled CO monitoring results and a significance of environmental CO exposure in areas with high pollution.

Pilot investigation: randomized-controlled analog trial for alcohol and tobacco smoking co-addiction using contingency management

Contingency management (CM) is associated with decreases in off-target drug and alcohol use during primary target treatment. The primary hypothesis for this trial was that targeting alcohol use or tobacco smoking would yield increased abstinence in the opposite, nontargeted drug. We used a 2 [CM vs. noncontingent control (NC) for alcohol]×2 (CM vs. NC for smoking tobacco) factorial design, with alcohol intake (through urinary ethyl glucuronide) and tobacco smoking (through urinary cotinine) as the primary outcomes. Thirty-four heavy-drinking smokers were randomized into one of four groups, wherein they received CM, or equivalent NC reinforcement, for alcohol abstinence, smoking abstinence, both drugs, or neither drug. The CM for alcohol and tobacco group had only two participants and therefore was not included in analysis. Compared with the NC for alcohol and tobacco smoking group, both the CM for the tobacco smoking group [odds ratio (OR)=12.03; 95% confidence interval (CI): 1.50-96.31] and the CM for the alcohol group (OR=37.55; 95% CI: 4.86-290.17) submitted significantly more tobacco-abstinent urinalyses. Similarly, compared with the NC for the alcohol and tobacco group, both the CM for smoking (OR=2.57; 95% CI: 1.00-6.60) and the CM for alcohol groups (OR=3.96; 95% CI: 1.47-10.62) submitted significantly more alcohol-abstinent urinalyses. These data indicate cross-over effects of CM on indirect treatment targets. Although this is a pilot investigation, it could help to inform the design of novel treatments for alcohol and tobacco co-addiction.

[Relationship between cigarette smoking and the carbon monoxide concentration in the exhaled breath with perioperative respiratory complications]

BACKGROUND

The purpose of the current study was to determine the effects of preoperative cigarette smoking and the carbon monoxide level in the exhaled breath on perioperative respiratory complications in patients undergoing elective laparoscopic cholecystectomies.

METHODS

One hundred and fifty two patients (smokers, Group S and non-smokers, Group NS), who underwent laparoscopic cholecystectomies under general anesthesia, were studied. Patients completed the Fagerstrom Test for Nicotine Dependence. The preoperative carbon monoxide level in the exhaled breath levels were determined using the piCO+Smokerlyzer 12h before surgery. Respiratory complications were recorded during induction of anesthesia, intraoperatively, during extubation, and in the recovery room.

RESULTS

Statistically significant increases were noted in group S with respect to the incidence of hypoxia during induction of anesthesia, intraoperative bronchospasm, bronchodilator treatment intraoperatively, and bronchospasm during extubation. The carbon monoxide level in the exhaled breath and the Fagerstrom Test for Nicotine Dependence, and number of cigarettes smoked 12h preoperatively were designated as covariates in the regression model. Logistic regression analysis of anesthetic induction showed that a 1 unit increase in the carbon monoxide level in the exhaled breath level was associated with a 1.16 fold increase in the risk of hypoxia (OR=1.16; 95% CI 1.01-1.34; p=0.038). Logistic regression analysis of the intraoperative course showed that a 1 unit increase in the number of cigarettes smoked 12h preoperatively was associated with a 1.16 fold increase in the risk of bronchospasm (OR=1.16; 95% CI 1.04-1.30; p=0.007). While in the recovery room, a 1 unit increase in the Fagerstrom Test for Nicotine Dependence score resulted in a 1.73 fold increase in the risk of bronchospasm (OR=1.73; 95% CI 1.04-2.88; p=0.036).

CONCLUSIONS

Cigarette smoking was shown to increase the incidence of intraoperative respiratory complications while under general anesthesia. Moreover, the estimated preoperative carbon monoxide level in the exhaled breath level may serve as an indicator of the potential risk of perioperative respiratory complications.

Salivary cotinine concentration and carbon monoxide levels in young adults smoking midwakh in comparison with cigarette smokers

Objectives

To estimate and compare the salivary cotinine levels using a semiquantitative method, called NicAlert, between three groups: non-smokers, daily smokers of cigarettes and daily smokers of midwakh, and to compare the carbon monoxide (CO) levels among these groups.

Materials and methods

A total of 159 adult male volunteers aged 20 and above were included, with 54 current cigarette smokers, 52 current midwakh smokers and 53 non-smokers. Estimate of breath carbon monoxide and salivary cotinine were collected, as well as sociodemographic characteristics and details of smoking habits and second-hand smoke exposure among participants. Institutional review board approval was obtained and data were analysed using SPSS V.21 with the Kruskal-Wallis test used to obtain differences in the distribution.

Results

There was no significant difference in the median breath CO and salivary cotinine levels between cigarette and midwakh smokers. Levels of breath CO were significantly higher in cigarette and midwakh smokers as compared with non-smokers (19.5, 17.5 and 6.0, respectively, p<0.05); the same relationship was observed for cotinine levels among cigarette and midwakh smokers as compared with non-smokers (4.0, 3.0 and 0.0, respectively, p≤0.05). Additionally, the values of both salivary cotinine and breath CO increased with the frequency of tobacco use.

Conclusion

These are the first data that we are aware of that demonstrate that in terms of at least two key biomarkers of tobacco use, there are comparable levels of exposure between cigarettes and midwakh users, demonstrating a need for intensified attention to the use of midwakh.

Chromatographic analysis of VOC patterns in exhaled breath from smokers and nonsmokers

Cigarette smoking harms nearly every organ of the body and causes many diseases. The analysis of exhaled breath for exogenous and endogenous volatile organic compounds (VOCs) can provide fundamental information on active smoking and insight into the health damage that smoke is creating. Various exhaled VOCs have been reported as typical of smoking habit and recent tobacco consumption, but to date, no eligible biomarkers have been identified. Aiming to identify such potential biomarkers, in this pilot study we analyzed the chemical patterns of exhaled breath from 26 volunteers divided into groups of nonsmokers and subgroups of smokers sampled at different periods of withdrawal from smoking. Solid-phase microextraction technique and gas chromatography/mass spectrometry methods were applied. Many breath VOCs were identified and quantified in very low concentrations (ppbv range), but only a few (toluene, pyridine, pyrrole, benzene, 2-butanone, 2-pentanone and 1-methyldecyclamine) were found to be statistically significant variables by Mann-Whitney test. In our analysis, we did not consider the predictive power of individual VOCs, as well as the criterion of uniqueness for biomarkers suggests, but we used the patterns of the only statistically significant compounds. Probit prediction model based on statistical relevant VOCs-patterns showed that assessment of smoking status is heavily time dependent. In a two-class classifier model, it is possible to predict with high specificity and sensitivity if a subject is a smoker who respected 1 hour of abstinence from smoking (short-term exposure to tobacco) or a smoker (labelled "blank smoker") after a night out of smoking (long-term exposure to tobacco). On the other side, in our study "blank smokers" are more like non-smokers so that the two classes cannot be well distinguished and the corresponding prediction results showed a good sensitivity but low selectivity.

Effects of exercise training intensity on cardiac autonomic regulation in habitual smokers

BACKGROUND

The sympathoexcitatory effects of cigarette smoking cause an autonomic imbalance that may lead to cardiovascular disease. Aerobic training improves autonomic function by developing cardiorespiratory fitness; however, it is still uncertain whether aerobic training ameliorates the compromised autonomic modulation in smokers. This study aimed to investigate the effects of 8 weeks' aerobic training at different exercise intensities on autonomic regulation in habitual smokers.

METHODS

Healthy males (n = 34) were randomly assigned to a moderate-intensity aerobic training (MAT, 60% of heart rate reserve [HRR]), a high-intensity training group (HAT, 75% HRR), or a control group (CG). Training groups performed 8 weeks' aerobic training on a treadmill (3 times/week), but all subjects continued to smoke cigarettes as usual. Heart rate variability was monitored to evaluate the effect of aerobic training on autonomic regulation.

RESULTS

Aerobic training improved autonomic balance despite the continued smoking. In the time domain, rMSSD and pNN50 were significantly increased in HAT than in CG. On spectral analysis, the absolute and normalized units of high frequency (HF) were significantly increased in HAT, whereas the LF/HF ratio and the normalized unit of LF were significantly decreased compared to that in CG. SD1 and the SD1/SD2 ratio of the Poincaré plot analysis were significantly increased compared to CG. Although MAT showed a similar tendency to HAT in nonlinear indexes, there were no significant differences compared to CG.

CONCLUSION

Aerobic training, particularly high-intensity training, increases the parasympathetic contribution to the sympathovagal system, leading to an improvement in autonomic balance despite continued cigarette smoking.

Influence of air pollution on exhaled carbon monoxide levels in smokers and non-smokers. A prospective cross-sectional study

BACKGROUND

The poor air quality and cigarette smoking are the most important reasons for increased carbon monoxide (CO) level in exhaled air. However, the influence of high air pollution concentration in big cities on the exhaled CO level has not been well studied yet.

OBJECTIVES

To evaluate the impact of smoking habit and air pollution in the place of living on the level of CO in exhaled air.

METHODS

Citizens from two large cities and one small town in Poland were asked to complete a survey disclosing their place of residence, education level, work status and smoking habits. Subsequently, the CO level in their exhaled air was measured. Air quality data, obtained from the Regional Inspectorates of Environmental Protection, revealed the differences in atmospheric CO concentration between locations.

RESULTS

1226 subjects were divided into 4 groups based on their declared smoking status and place of living. The average CO level in exhaled air was significantly higher in smokers than in non-smokers (p<0.0001) as well as in non-smokers from big cities than non-smokers from small ones (p<0.0001). Created model showed that non-smokers from big cities have odds ratio of 125.3 for exceeding CO cutoff level of 4ppm compared to non-smokers from small towns.

CONCLUSIONS

The average CO level in exhaled air is significantly higher in smokers than non-smokers. Among non-smokers, the average exhaled CO level is significantly higher in big city than small town citizens. These results suggest that permanent exposure to an increased concentration of air pollution and cigarette smoking affect the level of exhaled CO.

Feasibility of a Peer-Led Asthma and Smoking Prevention Project in Australian Schools with High Indigenous Youth

BACKGROUND

The high global burden of asthma and tobacco smoking among Indigenous people may potentially be reduced by appropriate interventions that target prevention of tobacco smoke uptake and improved asthma management. The latter includes targeted treatment based on airway inflammation. We undertook a feasibility study in two Darwin schools with a high proportion of Indigenous youth to determine the feasibility of an innovative, peer-led, school-based education program called the Asthma and Smoking Prevention Project (ASPP). A subset of children with reported persistent respiratory symptoms were also clinically evaluated to determine the lower airway inflammatory profile and optimize asthma management.

METHODS

The ASPP is founded on an evidence-based three-step program and targets improving asthma management and preventing the uptake of tobacco smoking. The program uses a student-centered approach in which senior students (peer leaders) deliver the ASPP to Grade 7 students using activities, videos, and games. Students completed questionnaires related to asthma and smoking at baseline and 3 months after program delivery. Students with respiratory symptoms at 3 months were invited for a comprehensive clinical evaluation and tests including sputum induction.

RESULTS

The ASPP was well received. Of the 203 students involved, 56 (28%) were Indigenous and 70% completed baseline and follow-up questionnaires. Self-reported asthma was high (19%), 10% of students reported smoking and 63% reported exposure to tobacco at home. Of the 22 students who were clinically evaluated, 41% were Indigenous. Clinically important airway inflammation was high; 23% had Fractional Exhaled Nitric Oxide Levels ≥35 ppb, 88% had airway neutrophilia (>15%), and 29% had airway eosinophilia (>2.5%). Optimization of medication and management was required in 59% of students.

CONCLUSION

Our study has demonstrated the implementation of the ASPP was well received by the schools as well as by the students. The high prevalence of clinically important airway inflammation and suboptimal asthma management highlights the need for a community-based study on persistent respiratory symptoms in adolescents to reduce the burden of chronic lung disease particularly for Indigenous Australians.

Should the threshold for expired-air carbon monoxide concentration as a means of verifying self-reported smoking abstinence be reduced in clinical treatment programmes? Evidence from a Malaysian smokers' clinic

BACKGROUND

It has been proposed that the expired-air carbon monoxide (CO) threshold for confirming smoking abstinence in clinical practice be reduced below 10 ppm. Optimal thresholds may vary across regions. Data are needed to assess the impact of such a change on claimed success.

METHODS

A total of 253 smokers who attended the Tanglin quit smoking clinic in Malaysia were followed-up 1, 3 and 6 months after the target quit date. All participants received a standard behavioural support programme and were prescribed either varenicline or nicotine replacement therapy. Expired-air CO was measured at every visit. Respondents' smoking status was assessed using a range of different CO thresholds (3, 5 and 10 ppm) and the impact on quit rates was calculated. Predictors of success as defined using the different thresholds were assessed.

RESULTS

The 6-month abstinence rates were: 1 month - 54.9% at 10 ppm, 54.9% at 5 ppm and 48.6% at 3 ppm; 3 months - 36.0% at 10 ppm, 35.2% at 5 ppm and 30.4% at 3 ppm; 6 months - 24.1% at 10 ppm, 24.1% at 5 ppm and 20.6% at 3 ppm. Older smokers were more likely to be recorded as abstinent at 6 months regardless of the threshold used.

CONCLUSIONS

Reducing the threshold for expired-air carbon monoxide concentrations to verify claimed smoking abstinence from 10 ppm to 5 ppm makes minimal difference to documented success rates in Malaysian smoker's clinic patients. Reducing to 3 ppm decreases success rates slightly. Predictors of success at stopping appear to be unaffected by the threshold used.