| Summary: | Introduction
The mobile-phone-based Bedfont iCO TM Smokerlyzer ® is of unknown
validity and reproducibility compared to the widely-used piCO + Smokerlyzer ® .
We aimed to compare the validity and reproducibility of the iCO TM Smokerlyzer ®
with the piCO + Smokerlyzer ® among patients reducing or quitting tobacco
smoking.
Material and Methods
Methadone-maintained therapy (MMT) users from three centers in
Malaysia had their exhaled carbon monoxide (eCO) levels recorded via the piCO +
and iCO TM Smokerlyzers ® , their nicotine dependence assessed with the Malay
version of the Fagerström Test for Nicotine Dependence (FTND-M), and daily
tobacco intake measured via the Opiate Treatment Index (OTI) Tobacco Q-score.
Pearson partial correlations were used to compare the eCO results of both devices,
as well as the corresponding FTND-M scores.
Results
Among the 146 participants (mean age 47.9 years, 92.5% male, and 73.3%
Malay ethnic group) most (55.5%) were moderate smokers (6–19 cigarettes/
day). Mean eCO categories were significantly correlated between both devices
(r=0.861, p<0.001), and the first and second readings were significantly correlated
for each device (r=0.94 for the piCO + Smokerlyzer ® , p<0.001; r=0.91 for the
iCO TM Smokerlyzer ® , p<0.001). Exhaled CO correlated positively with FTND-M
scores for both devices. The post hoc analysis revealed a significantly lower iCOTM
Smokerlyzer ® reading of 0.82 (95% CI: 0.69–0.94, p<0.001) compared to that
of the piCO + Smokerlyzer ® , and a significant intercept of -0.34 (95% CI: -0.61
– -0.07, p=0.016) on linear regression analysis, suggesting that there may be a
calibration error in one or more of the iCO TM Smokerlyzer ® devices.
Conclusions
The iCO TM Smokerlyzer ® readings are highly reproducible compared
to those of the piCO + Smokerlyzer ® , but calibration guidelines are required
for the mobile-phone-based device. Further research is required to assess
interchangeability.
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