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Sample Size Calculations for Detecting Disease-Modifying Osteoarthritis Drug Effects on Knee Replacement Incidence in
Janina S Ried1, Klaus Flechsenhar1, Eckart Bartnik1
1Sanofi-Aventis Deutschland GmbH, Frankfurt am Main, Germany.
Objective:
To evaluate the extent to which the current designs of clinical trials in knee osteoarthritis (OA) permit detection of a therapeutic effect of disease-modifying OA drugs (DMOADs) on the incidence of knee replacement, and to provide estimates of the required sample sizes.
Methods:
We selected distinct subcohorts of the Osteoarthritis Initiative (OAI), based on available information on eligibility criteria for clinical knee OA trials (ClinicalTrials.gov) and additional subcohorts stratified for age, sex, and the severity of radiographic OA. The observed incidence of knee replacement in these OAI subcohorts was used to estimate the expected incidence of knee replacement in the control group of a clinical trial. Based on this estimate, the sample sizes required to detect hypothetical treatment effects on the incidence of knee replacement were calculated, assuming observation periods of 2, 5, or 7 years.
Results:
The cumulative knee replacement incidence rates in the OAI subcohorts ranged from 0.9% to 12.9%. The corresponding sample sizes required to detect 50% improvement by the DMOAD, with a power of 80% and 95% confidence, were 5,459 and 362, respectively. Including only women with advanced age and radiographic OA increased the incidence of knee replacement and decreased the required sample size.
Conclusion:
The sample sizes that are commonly used in clinical trials do not enable the effects of a DMOAD on incident knee replacement to be detected with sufficient power and confidence. The estimated incidence rates of knee replacement and the corresponding sample sizes are important for informing the design of trials for disease course-modifying effects as well as for socioeconomic evaluation of a DMOAD in terms of preventing knee replacement.
Insights
Current clinical trial designs for knee osteoarthritis (OA) often lack the necessary sample size to detect the effectiveness of disease-modifying OA drugs (DMOADs) in preventing knee replacement. Larger sample sizes are crucial for robust trial outcomes.
Area of Science:
- Orthopedics
- Rheumatology
- Clinical Pharmacology
Background:
- Knee osteoarthritis (OA) is a leading cause of disability, with knee replacement surgery being a common outcome.
- Disease-modifying osteoarthritis drugs (DMOADs) aim to alter the disease course, but their effect on preventing knee replacement is not well-established.
- Current clinical trial designs may be underpowered to detect significant effects of DMOADs on knee replacement incidence.
Purpose of the Study:
- To assess the adequacy of current clinical trial designs for detecting DMOAD efficacy on knee replacement incidence.
- To estimate the sample sizes required for future trials investigating DMOADs.
Main Methods:
- Utilized subcohorts from the Osteoarthritis Initiative (OAI) based on clinical trial eligibility criteria.
- Stratified OAI subcohorts by age, sex, and radiographic OA severity.
- Calculated required sample sizes to detect hypothetical DMOAD treatment effects on knee replacement incidence.
Main Results:
- Knee replacement incidence in OAI subcohorts varied from 0.9% to 12.9%.
- Sample sizes needed to detect a 50% DMOAD effect ranged from 362 to 5,459, depending on the observation period (2-7 years).
- Subcohorts of older women with severe radiographic OA showed higher incidence and required smaller sample sizes.
Conclusions:
- Commonly used sample sizes in knee OA trials are insufficient to reliably detect DMOAD effects on knee replacement incidence.
- Accurate incidence rates and sample size estimations are vital for designing effective DMOAD trials and evaluating their socioeconomic impact.
