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dc.contributor.authorBessing, Barnabasen_UK
dc.contributor.authorBauld, Lindaen_UK
dc.contributor.authorSinclair, Lesleyen_UK
dc.contributor.authorMackay, Daniel Fen_UK
dc.contributor.authorTappin, Daviden_UK
dc.contributor.authorSpence, Williamen_UK
dc.description.abstractBackground  The limited representativeness of trial samples may restrict external validity. The aim of this study was to ascertain the representativeness of the population enrolled in the Cessation in Pregnancy Incentives Trial (CPIT), a therapeutic exploratory study to examine the effectiveness of financial incentives for smoking cessation during pregnancy.  Methods  CPIT participants (n = 492) were compared with all self-reported smokers at maternity booking who did not participate in the trial (n = 1982). Both groups were drawn from the National Health Service (NHS) Greater Glasgow and Clyde area over a 1-year trial enrolment period. Variables used for comparison were age, area-based deprivation index, body mass index, gestation, and carbon monoxide (CO) breath test level. Chi-square and Mann-WhitneyUtests were used to compare groups.  Results  From January to December 2012, 2474/13,945 (17.7%) women, who booked for maternity care, self-reported as current smokers (at least one cigarette in the last week). Seven hundred and fifty-two were ineligible for trial participation because of a CO breath test level of less than 7 parts per million (ppm) used as a biochemical cut-off to corroborate self-report of current smoking. At telephone consent 301 could not be contacted, 11 had miscarried, 16 did not give consent and 3 opted out after randomisation, leaving 492 participants for analysis. There were no differences in demographic or clinical characteristics between trial participants, and self-reported smokers not enrolled in the trial in terms of CO breath test (as a measure of smoking level for those with a CO level of 7ppm or higher), material deprivation (using an area-based measure), maternal age and maternal body mass index. Gestation at booking was statistically significantly lower for participants.  Conclusions  To ensure that all trial participants were smokers, biochemical validation excluded self-reported smokers with a CO level of less than 7ppm from taking part in the trial, which excluded 30% of self-reported smokers who were ‘lighter’ smokers. The efficacy of financial incentives would not have been likely to decrease if ‘lighter’ smokers had been included in the trial population. Trial participants were slightly earlier in their pregnancy at maternity booking, but this difference would not clinically affect the provision of financial incentives if provided routinely. Overall, the trial population was representative of all self-reported smokers with regard to available routinely collected data. Appropriate comparison of trial and target populations, with detailed reporting of exclusion criteria would contribute to the understanding of the wider applicability of trial results.en_UK
dc.publisherBioMed Centralen_UK
dc.relationBessing B, Bauld L, Sinclair L, Mackay DF, Tappin D & Spence W (2016) Representativeness of the participants in the smoking Cessation in Pregnancy Incentives Trial (CPIT): A cross-sectional study. Trials, 17, Art. No.: 426.
dc.rights© The Author(s). 2016 This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.en_UK
dc.subjectClinical markersen_UK
dc.subjectCross-sectional studiesen_UK
dc.subjectData collectionen_UK
dc.subjectTreatment effectivenessen_UK
dc.titleRepresentativeness of the participants in the smoking Cessation in Pregnancy Incentives Trial (CPIT): A cross-sectional studyen_UK
dc.typeJournal Articleen_UK
dc.type.statusVoR - Version of Recorden_UK
dc.contributor.affiliationWorld Health Organizationen_UK
dc.contributor.affiliationInstitute for Social Marketingen_UK
dc.contributor.affiliationInstitute for Social Marketingen_UK
dc.contributor.affiliationUniversity of Glasgowen_UK
dc.contributor.affiliationInstitute for Social Marketingen_UK
dc.contributor.affiliationUniversity of Glasgowen_UK
rioxxterms.apcnot requireden_UK
rioxxterms.typeJournal Article/Reviewen_UK
local.rioxx.authorBessing, Barnabas|en_UK
local.rioxx.authorBauld, Linda|en_UK
local.rioxx.authorSinclair, Lesley|0000-0002-2210-8181en_UK
local.rioxx.authorMackay, Daniel F|en_UK
local.rioxx.authorTappin, David|en_UK
local.rioxx.authorSpence, William|en_UK
local.rioxx.projectInternal Project|University of Stirling|
local.rioxx.filenameparticipants in CPIT.pdfen_UK
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