Table 1.
Comparison of the design of 2 randomised controlled trials for vasculitis: MYPAN versus MYCYC.
Fig 1.
Range of prior opinions elicited before introduction of the MYCYC data.
Fig 1A) Comparison of Expert A’s prior densities for pC and pM. Expert A thought the most likely value of pC is 0.65 and was 75% confident that pC exceeds 0.45. Expert A was optimistic about the relative efficacy of MMF stating that the chance that MMF is superior to CYC is 63% while the chance it is inferior to CYC is 5%. Fig 1B) Comparison of Expert B’s prior densities for pC and pM. Expert B thought the most likely value of pC is 0.8 and was 75% confident that pC exceeds 0.55. Expert B was more sceptical about the benefits of MMF, stating that the chance that MMF is superior to CYC is 10% while the chance it is inferior to CYC is 50%. Given each expert’s prior opinion about pC and the relative efficacies of MMF and CYC, a consistent prior for pM is derived.
Fig 2.
Flow diagram illustrating the sequence of activities undertaken during the MYPAN prior elicitation meeting and the time allocated to each activity.
Fig 3.
Expert prior opinion before introduction of the MYCYC data regarding 6-month remission rates using treatment with CYC or MMF for children with PAN.
Reprinted from [7] under a CC BY license, with permission from the authors, original copyright 2014. Prior opinion was that the most likely value for pC was 0.7; 90% and 50% credibility intervals were (0.30, 0.91) and (0.50, 0.78), respectively. The effective sample size was 5 patients on CYC. The prior for pM is derived from those for pC and θ. It had mode = 0.65; 90% and 50% credibility intervals were (0.21, 0.90) and (0.41, 0.74), respectively.
Fig 4.
Influence of the MYCYC trial results on expert prior opinion regarding 6-month remission rates using treatment with CYC or MMF for children with PAN. Reprinted from [7] under a CC BY license, with permission from the authors, original copyright 2014.
Fig 4A): Influence of MYCYC results on prior opinion for pC. The modified prior distribution for pC after considering the MYCYC results had mode = 0.74; 90% and 50% credibility intervals were (0.51, 0.86) and (0.63, 0.78), respectively. This level of certainty is equivalent to what would be obtained from a clinical trial involving 17 patients treated with CYC (effective sample size). Fig 4B): Influence of MYCYC results on prior opinion for pM. The modified prior for pM after considering the MYCYC results had mode = 0.71; 90% and 50% credibility intervals were (0.45, 0.85) and (0.59, 0.76), respectively. Fig 4C): Comparison of the final expert prior opinions for pC and pM incorporating the MYCYC data.
Fig 5.
Posterior densities for pC and pM based on the prior of Fig 4 following observation of 20 patients treated on each study arm, with 14/20 successes on CYC and 14/20 successes on MMF (Hypothetical Scenario 1), or with 14/20 successes on CYC and 7/20 successes on MMF (Hypothetical Scenario 2). Fig 5A) and 5C) are reprinted from [7] under a CC BY license, with permission from the authors, original copyright 2014.
Fig 5A): Prior and posterior densities for pC in Hypothetical Scenario 1. Fig 5B): Prior and posterior densities for pM in Hypothetical Scenario 1. Fig 5C): Prior and posterior densities for pC in Hypothetical Scenario 2. Fig 5D): Prior and posterior densities for pM in Hypothetical Scenario 2.