Kent Robert Johnson

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BACKGROUND The duration and cost of cancer clinical trials could be reduced if a surrogate endpoint were used in place of survival. We did a meta-analysis to assess the extent to which two surrogates, tumour response and time to progression, are predictive of mortality in metastatic colorectal cancer and non-small-cell lung cancer. METHODS Summary data(More)
We evaluate measurement properties of common rheumatoid arthritis (RA) assessments. Included are a comprehensive literature review and new data on the reliability and smallest detectable difference (SDD) for different classes of these measures. We found that certain common measures such as joint counts, pain, and patient global all had poor reliability and(More)
Agreement on response criteria in rheumatoid arthritis (RA) has allowed better standardization and interpretation of clinical trial reports. With recent advances in therapy, the proportion of patients achieving a satisfactory state of minimal disease activity (MDA) is becoming a more important measure with which to compare different treatment strategies.(More)
OBJECTIVE There are clear advantages to using biomarkers and surrogate endpoints, but concerns about clinical and statistical validity and systematic methods to evaluate these aspects hinder their efficient application. Our objective was to review the literature on biomarkers and surrogates to develop a hierarchical schema that systematically evaluates and(More)
BACKGROUND In metastatic renal cell cancer (mRCC) trials, progression-free survival (PFS) is increasingly used instead of overall survival (OS) as the approval end point. Unlike other solid tumors, there is no published demonstration of what PFS is needed across and by treatment class in mRCC. We determine this and evaluate drug approval decisions in mRCC(More)
OBJECTIVE The OMERACT Drug Safety Working Group focuses on standardization of assessment and reporting of adverse events in clinical trials and longitudinal and observational studies in rheumatology. This group developed the Rheumatology Common Toxicity Criteria (RCTC) in 1999, building on the Oncology Common Toxicity Criteria. At OMERACT 8, a workshop(More)
The OMERACT 6 Minimal Clinically Important Difference/Low Disease Activity Workshop was organized with the aim of meeting the many challenges that exist in determining a low disease activity in rheumatoid arthritis (RA). This article presents an overview of that workshop, including results of the voting, a summary of associated discussions, recommendations,(More)
The MCID (minimal clinically important difference) module of OMERACT 5 developed a research agenda that led to the conclusion that a state of low disease activity for rheumatoid arthritis (RA) would need to be defined. To develop such a definition the various concepts and terminologies, the process for developing an operational definition, and the(More)
The reports of associations between albuminuria and estimated glomerular filtration rate and mortality are a major advance in understanding the progression of renal disease and its sequelae. These findings reinforce the importance of population risk profiling. However, application is limited by validity concerns due to substantial unexplained heterogeneity(More)