Cost consequences analysis of physiotherapy in the management of hip or knee osteoarthritis

Abstract

Osteoarthritis (OA) is a major source of pain and morbidity, and is responsible for a substantial economic burden worldwide. International guidelines recommend conservative treatments such as exercise and physiotherapy as first-line interventions when managing patients with hip or knee OA; however, little is known about their value for money.

The objectives of this research were to: 1) assess the cost effectiveness of conservative treatments for OA by performing a systematic review of the literature; 2) develop and validate a questionnaire that collects data on health resource use and costs in patients with hip or knee OA; and 3) investigate the cost effectiveness of three physiotherapy programmes for the treatment of hip or knee OA.

The systematic review assessed the current evidence for the cost effectiveness of conservative interventions in the management of hip or knee OA. Of 11 studies included, five satisfied the criteria for high quality. The best value for money intervention appears to be group exercise led by a physiotherapist.

The Osteoarthritis Cost and Consequences Questionnaire was developed to collect OA-related health resource use and cost data and was validated against four administrative databases (n=50). Acceptable sensitivity (range 44%-100%) and specificity (range 59%-100%) levels were found for most health services. The numbers of visits ρc = 0.41 (95% CI: 0.19, 0.64) and medications ρc = 0.63 (95% CI:0.42, 0.78) and total cost estimate ρc = 0.997 (95% CI: 0.996, 0.999) derived from the questionnaire agreed with database records.

The economic evaluation was performed alongside a randomised controlled trial (n=206) investigating the effectiveness of three interventions relative to usual care. The analysis perspectives were from the New Zealand health system and society. As a cost consequences analysis, it included the quality-adjusted life year (QALY) as an economic endpoint, and disease-specific measures as clinical endpoints at one year. Willingness-to-pay thresholds of 1-3 × New Zealand’s GDP per capita were used to define value for money. Six sensitivity analyses were performed.

Each treatment gained incremental QALYs (each relative usual care); this was significant for exercise therapy, 0.026 (95% CI: 0.010, 0.042). From the New Zealand health system perspective costs were higher across all treatment groups. Exercise therapy was the only treatment to produce an incremental cost per QALY under 2 × GDP per capita (2009 New Zealand dollars) of $44 058 (95% CI: −70 885, 194 558). From the societal perspective, manual therapy was cost saving and best value for money. For the majority of scenarios considered, exercise therapy was more cost effective than usual care and combined therapy was only cost effective for participants who did not receive joint replacement surgery during the trial. Each respective therapy showed a higher probability of being cost effective relative to usual care when clinical versus economic outcomes were considered, and for participants not receiving joint replacement surgery during the trial.

The findings from this thesis contribute to current knowledge in multiple disciplines including the economic evaluation, health services research, OA, and physiotherapy literature. Conclusions from this body of research help fill gaps in the literature and answer calls from clinical guidelines to assess the cost effectiveness of complex physiotherapy programmes in treating patients with hip or knee OA.