Impact of Initiating Tiotropium Alone Versus Initiating Tiotropium in Combination With Fluticasone Propionate/Salmeterol Xinafoate Combination (FSC) on Chronic Obstructive Pulmonary Disease-related Outcomes in Patients With Pre-existing Exacerbations

This was a retrospective cohort design using administrative claims data from Jan 1, 2003 through Sep 30, 2007, representing the years of available data, were used for this study. Managed care enrollees having at least one pharmacy claim for tiotropium (TIO) during the study period were identified as the target population. An index TIO prescription was defined as the first chronologically occurring pharmacy claim for TIO during the period Jan 1, 2004 to Aug 31, 2006, called the enrollment period. The date of the index TIO prescription was termed as the index Rx date, and the 1-year period before the index Rx date was termed as the pre-index period. The period after the index date was termed as the post-index date, and is further divided into a 30-day combination assessment period and a 1-year follow-up period. COPD clinical and economic outcomes were measured in a variable length follow up period.

The combination assessment period, defined as the 30-day period following the index Rx date, was used to categorize patients into 2 cohorts: TIO alone or TIO + FSC (fluticasone propionate/salmeterol xinofoate combination) depending on whether they use FSC in combination with TIO during this period. Combination therapy with TIO + FSC was defined as having an FSC claim on the same date as the TIO claim or a TIO and FSC pharmacy claim with overlapping days supply occurring within 30 days of index Rx date. Enrollees adding FSC for the first time after the 30-day combination assessment period were excluded from the sample, thus ensuring that the TIO-alone cohort is not using FSC. No outcomes were assessed in the 30-day combination assessment period. The 1-year period after the end of the 30-day combination assessment period was termed as the follow-up period and was used to assess all study outcomes. Enrollees were required to be continuously eligible in their health plans during the pre-index and post-index periods for a total of 25 months. An intent-to-treat approach was used for the analyses. Thus, patients identified to be in a drug therapy cohort were considered to be using that therapy during the entire follow-up period, regardless of therapy discontinuations.

Specifically the study hypothesis for the primary outcome being tested was:

Ho: There is no difference in risk of any COPD-related exacerbation between TIO+FSC and TIO cohorts Ha: There is a difference in risk of any COPD-related exacerbation between TIO+FSC and TIO cohorts

Hypothesis for the key secondary outcome of COPD-related costs that was tested was:

Ho: There is no difference in COPD-related costs between TIO+FSC and TIO cohorts Ha: There is a difference in COPD-related costs between TIO+FSC and TIO cohorts