Response to Letter to the Editor

Abstract

Dr Chitsaz points out several concerns about our study. Most of the criticism stems from the lack of follow-up data on the complete cohort. They are correct in pointing out that the final sample in study II represents just 57% of the original 84 participants enrolled in study I. Follow-up information on deceased or lost to follow-up participants was, by definition, unavailable. As a consequence, we were unable to comment on the correlation of adherence rates in these participants between the 2 studies. We agree with Dr Chitsaz that it is likely that these individuals had more advanced disease. It is also reasonable to consider that survivor bias may have selected for a cohort with better outcomes in study II. Whether those who died or were lost to follow-up would have had poorer correlation of adherence rates between the 2 time points is purely speculative. With regard to the participants who switched to new regimens, 11 of the 12 switched from twice-daily to once-daily regimens. In contrast to the remainder of the cohort, adherence rates among these 12 increased, although not significantly, from study I to study II. It is likely that the lack of significant correlation in adherence rates in these participants was due to the change in the dosing schedule. Certainly, an idealized version of this study would have collected a complete complement of data on all participants. Nonetheless, the correlation of adherence rates between the 2 studies in the final cohort was noteworthy, particularly among the best adherers. The substantial lost to follow-up rate was acknowledged in the Discussion section, but we thank Dr Chitsaz for pointing out several potential biases that attrition from the study may have engendered.