This trial used a 2��2 factorial design (with randomization to Src Bosutinib NRT or placebo). As with all NARS trials, smoking reduction was the primary outcome. The secondary outcome was 2-month prolonged abstinence between months 2 and 4. If participants in the short reduction arm followed the program instructions and succeeded in stopping smoking, they would be counted as successes. However, those following the 6- to 9-month instructions, while not precluded from stopping smoking, were not instructed to do so until 6�C9 months. Thus, the prolonged abstinence measure is biased in this trial toward the 4-week reduction. Point prevalence abstinence would be biased in a similar direction. In our review (Wang et al., 2008), we extracted 7-day point prevalence at 12 months from this study.
By 12 months, relapse eroded more quitters from the 4-week reduction than from the 6- to 9-month reduction because the former had been abstinent longer; thus, assessing the outcome with point prevalence was biased in favor of the 6- to 9-month reduction. It is not possible to use a cessation measure tied to real time to measure the relative success of these two approaches to reducing and then stopping. Floating prolonged abstinence: a solution The key concept behind floating prolonged abstinence is that a person is counted as a success if that abstinence begins some time during the treatment phase of a study and is maintained for 6 months. This approach is true to the spirit of the SRNT procedures (Hughes et al., 2003) but adapts it to these kinds of trials. Consider the hypothetical trial and participants illustrated in Figure 1.
This trial is typical of NARS trials, with a treatment period of 12 months and last follow-up at 15 months. Participant 1 is a straightforward case. She maintained abstinence for two periods of 2 months and so failed to Batimastat maintain 6 months of abstinence. Participant 2 is straightforward because he ended the trial abstinent, having been abstinent for 6 months. Participant 3 would count as a treatment failure in a conventional assessment because he ended as a smoker. However, with our proposed outcome, he is a success because he succeeded in achieving 7 months of prolonged abstinence. Figure 1. Possible outcomes from a prolonged treatment trial. s, Smoking; Q, quit. Participant 4 is typical of people in an aid-to-cessation trial. He started abstinence early in treatment and relapsed after 5 months. In aid-to-cessation trials, resumed smoking would normally mean the participant, if he quit again, would use either no treatment or treatment obtained elsewhere but not the treatment to which he was randomized initially. (This is one reason why point prevalence abstinence can give misleading information.