ADOPTING THE PHASE-OF-CARE APPROACH TO ESTIMATE COSTS OF A SECONDARY DIAGNOSIS OF CLOSTRIDIUM DIFFICILE

Tuesday, October 21, 2014
Poster Board # PS3-36

Candidate for the Lee B. Lusted Student Prize Competition

Natasha Nanwa, MSc1, Jeffrey Kwong, MD, MSc2, Murray D. Krahn, MD, MSc3, Nick Daneman, MD, MSc4, Hong Lu, MSc, PhD2, Anand Govindarajan, MD, MSc5, Laura Rosella, MPH, PhD6, Suzanne Cadarette, MSc, PhD1 and Beate Sander, PhD7, (1)Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, ON, Canada, (2)Institute for Clinical Evaluative Sciences, Toronto, ON, Canada, (3)Toronto Health Economics and Technology Assessment (THETA) Collaborative, University of Toronto, Toronto, ON, Canada, (4)Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, ON, Canada, (5)Mount Sinai Hospital, Toronto, ON, Canada, (6)Ontario Agency for Health Protection and Promotion, Toronto, ON, Canada, (7)University of Toronto, Toronto, ON, Canada
Purpose: Our objective was to estimate phase-of-care-specific costs associated with a secondary diagnosis of Clostridium difficile (CD) from a healthcare payer perspective. 

Method: We conducted a retrospective incidence-based cost of illness (COI) analysis using health administrative data covering the population of Ontario (~13 million), Canada. We identified incident subjects with a secondary diagnosis of CD using the ICD-10-CA code A04.7 (enterocolitis due to CD). The phase-of-care approach was adopted, where each subject’s observation time was organized into phases: phase 1 (acute infection), phase 2 (continuing care), and phase 3 (final). We determined phase length by graphing costs and soliciting expert opinion. We matched infected subjects to uninfected subjects. Hard-match variables included age, sex, admission date, primary diagnosis, and the logit of the propensity score. Propensity score variables included income quintile, rurality, co-morbidities, institution, healthcare use, and antibiotic exposure. We standardized costs by estimating 30-day costs per phase (2012 Canadian dollars).

Result: From January 2003 to December 2010, we identified 21,771 subjects (mean=2,721/year), where 53% were female, and the mean age was 72 years (range=0-107). The lengths of phase 1 and 3 were 6 and 3 months, respectively. The length of phase 2 varied between 1 and 104 months. Mean 30-day phase 1, 2, and 3 costs per infected subject were $11,769 (range=$387-$201,236, n=10,251), $2,277 (range=$0-$137,320, n=8,454), and $18,918 (range=$0-$259,429, n=10,282), respectively. Mean 30-day phase 1, 2, and 3 costs per uninfected subject were $4,709 (range=$30-$98,365, n=10,251), $705 (range=$0-$33,483, n=8,454), and $9,962 (range=$0-$192,422, n=10,282), respectively. Attributable 30-day mean phase 1, 2, and 3 costs per subject were $7,060 (95%CI: $6,813-$7,295, n=10,251), $1,572 (95%CI:$1,471-$1,672, n=8,454), and $8,956 (95%CI:$8,557-$9,372, n=10,282), respectively. Greater attributable phase 1 and 3 costs were found in: males; those who died within one year of their admission date; those aged 19-64 years; those diagnosed in 2009; and those who underwent a colectomy procedure. Sensitivity analysis found costs to be sensitive to phase length.

Conclusion: A secondary diagnosis of CD significantly increases costs. The phase-of-care approach can be adopted to calculate the costs of CD. Decision makers and researchers can use these results to assess CD mitigation strategies such as vaccination and antibiotic stewardship programs.

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