Patients with PAH are confronted with a growing number of therapeutic options, each of which is associated with its own unique delivery system. Because little to no comparative effectiveness data exists, patient preferences can often be the driving factor behind choice of therapy. Thus, treatment satisfaction is likely to be highly relevant in the management of PAH. In this study, we evaluated the psychometric characteristics of a relatively new treatment satisfaction measure, the TSQM, assessed among patients participating in a 12 week open-label study of inhaled PAH therapy. We found that transitioning from inhaled iloprost to inhaled treprostinil was associated with significant improvements in treatment satisfaction as measured by the TSQM. Domains of treatment satisfaction impacted included global satisfaction, effectiveness, and convenience, but not side effects. Overall, the TSQM showed high internal consistency, good convergent validity, and evidence of responsiveness to change over 12 weeks. Increases in treatment satisfaction were significantly associated with improvement in QoL independent of subject characteristics.
Little is known about the determinants of treatment satisfaction in PAH. In a previous pilot study, we evaluated changes in treatment satisfaction using the TSQM among 10 patients with PAH transitioning from continuous intravenous epoprostenol to intravenous treprostinil . In that study, a significant impact was observed in all domains of the TSQM at 8 weeks. Changes in treatment satisfaction were accompanied by improvement in QoL scores and a decrease in total time spent on drug preparation activities. Based on these favorable results, we utilized a similar approach in designing the current study of inhaled prostacyclin among a substantially larger population of patients with PAH [17, 18]. Our findings support the reliability, validity, and responsiveness of the TSQM in PAH, while providing additional insights regarding its relationship with other health status measures.
In the case of inhaled prostacyclins, we found that global satisfaction with treatment appears to be most strongly associated with effectiveness of the medication as perceived by the patient. Significant correlations between change in treatment satisfaction and change in 6MWD further corroborate this finding. Nonetheless, convenience also appears to play a major role. Among the 4 treatment satisfaction domains, convenience appeared the most responsive to transition from inhaled iloprost to inhaled treprostinil. Parallel improvements in medication administration time were also observed, however, these changes did not correlate significantly with change in treatment satisfaction. One potential explanation for the lack of association is that additional factors (other than time spent administering medication) may have a significant impact on convenience. For example, particular features associated with the delivery device, such as ease of operation, need for cleaning/maintenance, and portability may be equally, or even more, important. Another explanation is that our study may not be adequately powered to detect weaker associations, although trends in the anticipated direction of effect were observed. In addition to convenience, side effects can also have a significant impact on treatment satisfaction as indicated by significant correlations with adverse events at week 12. In this study, however, we could not evaluate impact of changes in adverse events since they were not collected at baseline for iloprost. In spite of this, the lack of any change in the side effects domain of the TSQM suggests that treprostinil and iloprost may have similar side effect profiles.
Several limitations should be considered in the interpretation of our data. Most importantly, although the study was conducted in a prospective fashion, the relationships evaluated in our analysis utilized measures assessed concurrently. Consequently, causality cannot be inferred. Based on our findings, it is possible that improvement in 6MWD and reduction in medication administration time could have lead to the observed increase treatment satisfaction, but this remains speculative. Moreover, it is difficult to determine whether increased treatment satisfaction resulted in improved QoL, or vice versa. Cross-lagged panel models have been developed to address such temporal associations, but are require substantially more data. As previously mentioned, our small sample size also limits our ability to detect what may be modest, albeit meaningful relationships. Ideally, a varied range of responses is required in order to fully evaluate the responsiveness of an instrument. In the case of our results, our ability to demonstrate the responsiveness of the TSQM may have been limited by the fact that nearly all patients reported improvements in treatment satisfaction. Similar side effect profiles between the two inhaled prostacyclins may have also precluded our ability to assess responsiveness in this regard. Finally, our results are also vulnerable to potential selection bias insofar as patients who are currently dissatisfied with their current treatment (iloprost) may be more likely to have enrolled into the trial. Exclusion of patients with missing data for treatment satisfaction could have also introduced bias if the patients excluded were systematically different (e.g., more likely or less likely to be satisfied) than those included.
In summary, changes in treatment satisfaction in patients transitioning from inhaled iloprost to inhaled treprostinil were associated with increased exercise capacity and improved QoL. The TSQM demonstrates reasonable performance characteristics in patients with PAH and may be a useful tool for comparing satisfaction with PAH therapies, in particular, those requiring different delivery routes or dosing regimens.