Economic impact of tobramycin in patients with cystic fibrosis in a managed care population

Debra A. Wertz, Chun Lan Chang, Judith J. Stephenson, Jie Zhang, Robert J. Kuhn

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


Objective: Guidelines recommend chronic use of tobramycin solution for inhalation (TSI) for cystic fibrosis (CF) patients with moderate-to-severe lung disease and persistent airway Pseudomonas aeruginosa. This study evaluated the economic impact of TSI in managed care CF patients. Methods: Patients (064 years) with a2 CF medical claims between 01/01/0403/31/09 were identified. For TSI users, the index date was the first TSI claim in the period; for non-users, a pseudo-index date was determined and randomly assigned by simulating the distribution of index dates of TSI users. Maximum sample size was obtained for patients with a3 months pre- and a12 months post-index eligibility. Users were categorized by number of TSI prescriptions filled during 12-month post-index period as low (1 fill), medium (23 fills) and high adherence (a4 fills). Differences in per member per month (PMPM) costs pre-index to post-index were analyzed using paired t-tests. Results: A total of 388 TSI users (mean age 19 years, 48% female) and 444 non-users (mean age 30 years, 54% female) met study criteria. In users, total and CF-related PMPM costs decreased $959 (17%) and $113 (3%), respectively, after starting TSI. Among TSI users, CF-related inpatient PMPM costs decreased by $1171 (49%; p=0.01), while CF-related prescription PMPM costs increased by $992 (p<0.01). CF-related inpatient PMPM costs decreased by $381 (38%; p=0.16) for low and $1425 (50%; p=0.21) for medium users and decreased by $1829 (51%; p=0.02) for high users. Limitations: Limitations include use of administrative claims data, small sample size due to disease rarity, random assignment of pseudo-index date to non-users and differences in baseline characteristics between TSI users and non-users. Conclusion: All-cause and CF-related PMPM medical costs significantly decreased after TSI initiation. Among TSI users, total healthcare costs decreased, although not significantly, due to PMPM increases in prescription costs. A trend towards greater decrease in inpatient PMPM costs was observed with increasing TSI adherence.

Original languageEnglish
Pages (from-to)759-768
Number of pages10
JournalJournal of Medical Economics
Issue number6
StatePublished - Dec 2011

Bibliographical note

Funding Information:
JZ is a full-time employee of Novartis. RJK received consulting fees from Novartis Pharmaceuticals Corporation for research design, and data interpretation. DW and JS are employees of HealthCore Inc., which received funding from Novartis Pharmaceuticals Corporation for research and consulting services associated with this manuscript. CLC was an employee of HealthCore Inc. at the time this study was conducted.


  • Cost
  • Cystic fibrosis
  • Expenditures
  • Outcomes
  • Tobramycin

ASJC Scopus subject areas

  • Health Policy


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