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• Response to Impact vs. Efficacy for Pregnant Smokers
  Paul Aveyard
  Published on: 18 January 2006
• Impact vs. Efficacy for Pregnant Smokers
  James O Prochaska
  Published on: 17 July 2003

• Published on: 18 January 2006

  Response to Impact vs. Efficacy for Pregnant Smokers

  • Paul Aveyard, Senior Lecturer
  • Other Contributors:
    • Terry Lawrence, KK Cheng

  Prochaska and Velicer have commented on this trial(1), and, having been alerted to this comment elsewhere, we feel we need to respond belatedly. They suggest the study had important flaws but do not name them. We drew attention to those flaws in the conduct of the study in the report. The major flaw was that midwives in the control arm were less enthused about the intervention and complied with the protocol less well,...

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  Prochaska and Velicer have commented on this trial(1), and, having been alerted to this comment elsewhere, we feel we need to respond belatedly. They suggest the study had important flaws but do not name them. We drew attention to those flaws in the conduct of the study in the report. The major flaw was that midwives in the control arm were less enthused about the intervention and complied with the protocol less well, which overstated the benefit of the intervention, which we addressed in the report. In retrospect, it might also have been better to have had two larger arms than three.

  In addition, they state that this is a population-based trial and this is partly true- we certainly intended that it should be so- but the trial fell short of this ideal. We asked midwives to recruit every smoker into the trial regardless of willingness to stop smoking, but, as is clear from Figure 1, only a minority of smokers were approached. Nearly all those who were approached agreed. This was a cluster-randomised trial because we thought it would be difficult for midwives to switch counselling styles between the TTM-based approach and their normal approach. However, we trained midwives to approach participants in all arms of the study in the same way. That is, we asked midwives not to say to women in the control arm- you will receive my usual care- while for the intervention arms, midwives were asked not to describe the specific intervention a woman was to receive. Rather, midwives were trained to present the possibility that a woman would potentially receive any of the interventions, when in reality she could only receive one. To have done otherwise would have risked biasing the trial. Thus, any differences in the rate at which midwives approached women to participate in the trial were nothing to do with the attractiveness of the intervention. They were to do with the enthusiasm of the midwife as we discussed in the trial report. This may sound subtle but it is important. If the NHS had chosen to implement the TTM-based intervention, then as every midwife has to raise smoking and record it on the maternity record, if her standard intervention was now the TTM-based one, then all women who admitted to smoking would receive this intervention. Differences in uptake in the ‘real world’ outside this trial would not occur. Consequently, the eight times the population impact figure of Prochaska and Velicer is wrong, as the main driver of it is the uptake rates which would not differ outside a trial, where recruitment meant lots of extra work for the midwife.

  Prochaska and Velicer state that we recommend programmes with no evidence. Actually, the last sentence of our report was ‘Smoking in pregnancy is currently a problem for which there is no good currently available solution.’ We still believe this is true at a population level, but it also reasonable to suggest that all midwives should discuss smoking, as this seems like an ethical imperative. It seems reasonable also for midwives to offer assistance to stop, mainly referral to a specialist who can give that help, and there is good evidence that this is effective(2). I am pleased to say that one local service manages to see around half of all pregnant smokers, of whom a third of these set a quit date and around a quarter of those sustain validated 4-week abstinence. This clearly shows the small population impact- around 4% of all pregnant smokers (see http://www.uknscc.org/2005_UKNSCC/presentations/carmel_ogorman.html), but this is better than the population impact of the TTM-based interventions in our trial (where the comparable figure is 2-3%).

  One way to better understand the population impacts of the TTM-based interventions in pregnancy is to see more trials with similar interventions. Prochaska, Velicer and colleagues completed such a trial before ours was completed and it is still not published. Understanding the efficacy of these interventions would be improved if it were.

  Reference List

  (1) Lawrence PT, Aveyard P, Evans O, Cheng KK. A cluster randomised controlled trial of smoking cessation in pregnant women comparing interventions based on the transtheoretical (stages of change) model to standard care. Tobacco Control 2003; 12:168-177.

  (2) Lumley J, Oliver S, Waters E. Interventions for promoting smoking cessation during pregnancy (Cochrane Review). In: The Cochrane Library, Issue 1, 2003.

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  Conflict of Interest:
  None declared.

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• Published on: 17 July 2003

  Impact vs. Efficacy for Pregnant Smokers

  • James O Prochaska, Director and Professor
  • Other Contributors:
    • Wayne F. VelicerI

  Lawrence et al. (2003) reported the results of their cluster RCT on smoking cessation in pregnant women comparing (1) standard care; (2) Transtheoretical Model (TTM) based manuals; and (3) TTM computer based tailored communications.1 In spite of serious flaws in this study, there were very important results that the authors overlooked. They do not seem to appreciate that this was a population-based trial where the goal...

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  Lawrence et al. (2003) reported the results of their cluster RCT on smoking cessation in pregnant women comparing (1) standard care; (2) Transtheoretical Model (TTM) based manuals; and (3) TTM computer based tailored communications.1 In spite of serious flaws in this study, there were very important results that the authors overlooked. They do not seem to appreciate that this was a population-based trial where the goal is to reduce the prevalence of smoking in an important population, pregnant women. Their analyses treat the project as if it was a traditional clinical trial where the goal is to assess only efficacy.

  The most important analysis for a population trial is to assess the relative impacts of alternative treatment programs.2,3 Impact equals reach (or recruitment rate) times efficacy. Historically cessation programs were assessed just on efficacy. If one treatment program had 30% point prevalence abstinence at long-term follow-up, it was judged to be 50% more efficacious than a program with only 20% abstinence or efficacy. But if the first treatment reached only 5% of a population of smokers it would have an impact of only 1.5% (30% x 5%). It could reduce the prevalence of smoking in a population by only 1.5%. If the second treatment could recruit 60% of a population it would have 12% impact, or 8 times more impact than the treatment with greater efficacy. From a public health policy perspective, preference would be given to programs with the most impact.

  What were the relative impacts of three programs compared in Lawrence et al.? From the data reported, recruitment rates were calculated for each of the three groups by dividing the number of pregnant smokers recruited by the number of eligible smokers available in each group (Figure 1). Efficacy was calculated by the self-report prevalence rates at 10 days post-natal corrected by the mis-reporting rates for each group (Tables 6 & 7 in (1)). Self-reported point prevalence measures are what are used in determining population prevalence rates of smoking and are the measures used in the United States for the Public Health Service sponsored Clinical Practice Guidelines for Treating Tobacco.4

  The impact of each of the three treatments is

  A. Standard Care Impact = (23.3% recruited x 4.7 point prevalence) = 1.1%. B. TTM Manual Impact = (39.5% recruited x 7.5% point prevalence) = 3%. C. TTM Computer-tailored Impact = (58.5% recruited x 15.3% point prevalence) = 9%.

  The TTM Computer-tailored system had 8.2 times greater impact on the prevalence of smoking compared to Standard Care. The evidence reported by Lawrence et al. indicates that compared to standard care the TTM expert system intervention recruited and retained more pregnant smokers, produced less misreporting, helped more smokers quit, and had much greater impact. Is there any program that has been found to have greater advantages with a population of pregnant smokers?

  The authors recommend policies that have no evidence. They recommend, for example, that midwives proactively recruit pregnant smokers to existing smoking cessation programs (an alternative not evaluated in their study). In a study in the US of a similar procedure, a major health care system in the U.S. had doctors, nurses, health educators and telephone counselors all work proactively to get smokers in primary care to sign up for cessation programs that were only reaching 1% of eligible smokers.5 This proactive recruitment protocol, one of the most intensive in the literature, was able to get 15% of smokers in the precontemplation stage to sign up. But only 3% showed up. With a combined group in the contemplation and preparation stages, they were able to get 65% to sign up. But only 15% showed up. It is almost certain that the alternative policy recommended by Lawrence et al would have much less impact than the computer-based program that they reported. Based on the evidence that they report, we would recommend (1) that impact be used as the primary outcome criteria and (2) that the programs that have evidence of having the highest relative impacts for pregnant women be adopted. James O. Prochaska, Ph.D. and Wayne F. Velicer, Ph.D. Cancer Prevention Research Center, University of Rhode Island

  Correspondence to: James O. Prochaska, Ph.D. Cancer Prevention Research Center, University of Rhode Island 2 Chafee Rhode Island Kingston, Rhode Island 02881 USA jop@uri.edu velicer@uri.edu References 1. Lawrence, T., Aveyard, P., Evans, O., & Chang, K.K. (2003). A cluster randomized controlled trial of smoking cessation in pregnant women comparing interventions based on the Tran theoretical (stages of change) model to standard care. Tobacco Control. 2. Velicer, W.F., & DiClemente, C. C. (1993). Understanding and intervening with the total population of smokers. Tobacco Control, 2, 95- 96. 3. Velicer, W.F., & Prochaska, J.O. (1999). An expert system intervention for smoking cessation. Patient Education and Counseling, 36, 119-129. 4. Fiore, M.C., Bailey, W.C., Cohen, S.J., et al. (2000). Treating Tobacco Use and Dependence. Clinical Practice Guideline. Rockville, MD: Department of Health and Human Services. Public Health Service. 5. Lichtenstein, E., & Hollis, J. (1992). Patient referral to smoking cessation programs: Who follows through? The Journal of Family Practice, 34, 739-794.

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  Conflict of Interest:
  None declared.

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