The false economy of increased waiting times for hip and knee arthroplasty : a cost consequence analysis

Abstract

Aims: Cost per quality-adjusted life-year (QALY) can be used to estimate the financial consequences of delayed surgery. QALYs are determined by health-related quality of life (HRQoL) and the duration of the time spent in that state. Total hip arthroplasty (THA) and total knee arthroplasty (TKA) are cost-effective procedures, but it is not known whether prolonged waiting times have an impact on costs and QALYs associated with them. The aim of this study was to investigate how the time waiting for surgery can influence the overall cost and gains in QALYs over a ten-year period following THA or TKA.

Methods: Public data sources, including the National Joint Registry (NJR), NHS Digital patient-reported outcome measures (PROMs) and previously published studies were used to model HRQoL gains following THA and TKA. Using EuroQol five-dimension questionnaire (EQ-5D) index scores, the net QALY was simulated for waiting times of three months, one year and three years. Expected EQ-5D scores up to ten years postoperatively were plotted for THA and TKA. The trjectories of QALYs were modelled using probabilistic sensitivity analysis. Shortfalls in QALYs were calculated as the area under the curve (AUC).

Results: When the costs of additional prescriptions and unscheduled care were included, the excess cost incurred per patient by waiting three years compared to three months was £1,756 (£796 with disutility) for THA, and £2,116 (£1,068 with disutility) for TKA. Waiting one year resulted in a ten-year shortfall of QALYs of 9% for both THA and TKA, increasing to 45.5% (THA) and 57.1% (TKA) after a three-year wait. Three-year waits increased the cost/QALY by 2.00 to 2.44 times for THA (1.14 to 1.23 for one year) and 2.45 to 2.93 times (1.10 to 1.19 for one year) for TKA. If improvements in EQ-5D (as opposed to absolute values) were equal between the waiting times, waiting three years for TKA resulted in a net loss of QALYs over ten years.

Conclusion: This analysis suggests that waiting beyond three months for THA/TKA resulted in excess costs and diminished HRQoL. Increasing waiting times in the NHS, thus, appear to be a false economy.