Agreement between two methods of clinical measurement can be quantified using the differences between observations made using the two methods on the same subjects. The 95% limits of agreement, estimated by mean difference +/- 1.96 standard deviation of the differences, provide an interval within which 95% of differences between measurements by the two methods are expected to lie. We describe how graphical methods can be used to investigate the assumptions of the method and we also give confidence intervals. We extend the basic approach to data where there is a relationship between difference and magnitude, both with a simple logarithmic transformation approach and a new, more general, regression approach. We discuss the importance of the repeatability of each method separately and compare an estimate of this to the limits of agreement. We extend the limits of agreement approach to data with repeated measurements, proposing new estimates for equal numbers of replicates by each method on each subject, for unequal numbers of replicates, and for replicated data collected in pairs, where the underlying value of the quantity being measured is changing. Finally, we describe a nonparametric approach to comparing methods.

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Measuring agreement in method comparison studies

Radiomics, the high-throughput mining of quantitative image features from standard-of-care medical imaging that enables data to be extracted and applied within clinical-decision support systems to improve diagnostic, prognostic, and predictive accuracy, is gaining importance in cancer research. Radiomic analysis exploits sophisticated image analysis tools and the rapid development and validation of medical imaging data that uses image-based signatures for precision diagnosis and treatment, providing a powerful tool in modern medicine. Herein, we describe the process of radiomics, its pitfalls, challenges, opportunities, and its capacity to improve clinical decision making, emphasizing the utility for patients with cancer. Currently, the field of radiomics lacks standardized evaluation of both the scientific integrity and the clinical relevance of the numerous published radiomics investigations resulting from the rapid growth of this area. Rigorous evaluation criteria and reporting guidelines need to be established in order for radiomics to mature as a discipline. Herein, we provide guidance for investigations to meet this urgent need in the field of radiomics.

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Radiomics: the bridge between medical imaging and personalized medicine

Seventy-one "negative" randomized control trials were re-examined to determine if the investigators had studied large enough samples to give a high probability (greater than 0.90) of detecting a 25 per cent and 50 per cent therapeutic improvement in the response. Sixty-seven of the trials had a greater than 10 per cent risk of missing a true 25 per cent therapeutic improvement, and with the same risk, 50 of the trials could have missed a 50 per cent improvement. Estimates of 90 per cent confidence intervals for the true improvement in each trial showed that in 57 of these "negative" trials, a potential 25 per cent improvement was possible, and 34 of the trials showed a potential 50 per cent improvement. Many of the therapies labeled as "no different from control" in trials using inadequate samples have not received a fair test. Concern for the probability of missing an important therapeutic improvement because of small sample sizes deserves more attention in the planning of clinical trials.

The importance of beta, the type II error and sample size in the design and interpretation of the randomized control trial. Survey of 71 "negative" trials.

The purpose of evaluating public health surveillance systems is to ensure that problems of public health importance are being monitored efficiently and effectively. CDC's Guidelines for Evaluating Surveillance Systems are being updated to address the need for a) the integration of surveillance and health information systems, b) the establishment of data standards, c) the electronic exchange of health data, and d) changes in the objectives of public health surveillance to facilitate the response of public health to emerging health threats (e.g., new diseases). This report provides updated guidelines for evaluating surveillance systems based on CDC's Framework for Program Evaluation in Public Health, research and discussion of concerns related to public health surveillance systems, and comments received from the public health community. The guidelines in this report describe many tasks and related activities that can be applied to public health surveillance systems.

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Updated guidelines for evaluating public health surveillance systems: recommendations from the Guidelines Working Group.

Systems that extract structured information from natural language passages have been highly successful in specialized domains. The time is opportune for developing analogous applications for molecular biology and genomics. We present a system, GENIES, that extracts and structures information about cellular pathways from the biological literature in accordance with a knowledge model that we developed earlier. We implemented GENIES by modifying an existing medical natural language processing system, MedLEE, and performed a preliminary evaluation study. Our results demonstrate the value of the underlying techniques for the purpose of acquiring valuable knowledge from biological journals.

GENIES: a natural-language processing system for the extraction of molecular pathways from journal articles.

The Unified Medical Language System: an informatics research collaboration.

Not long ago medical research was mainly concerned with effects that were so large that statistics were of little relevance. In some cases this is still true, but more and more we are attempting to...

Statistics in medical research.

Studies in leukemia. VII. The induction of leukemia in Swiss mice by means of cell-free filtrates of leukemic mouse brain.

Computers are used to influence diagnostic and therapeutic decisions. The computer's information-handling capabilities allow it to serve as a reliable extension of the physician's memory and expander of the physician's information and synthesized knowledge resources. Computers have been used to facilitate decisions through organization of patient data, improved classification of patients, decision analysis in clinical settings, and simulation of expert clinical reasoning. Computer programs are more successful in narrow, constrained, single arenas of medicine with much underlying pathophysiologic understanding and where decisions are based largely on hard laboratory data. New models of synthetic reasoning that simulate expert clinical behavior show promise of supporting complicated decisions concerning problems of multiple diseases. All systems are confronted by problems of consensus and authority of the underlying information used.

Computer use in diagnosis, prognosis, and therapy.

FIVE CASES of hypernatremia (serum sodium levels above 150 mEq. per liter) associated with brain injury were reported by Allott 1 in 1939. Despite numerous subsequent reports, the frequency with which hypernatremia occurs has not been fully appreciated. Nor has our understanding of the mechanisms producing hypernatremia been greatly enhanced In the past four years we have encountered over 100 unequivocal instances of hypernatremia (hyperosmolarity) in acutely ill patients. It seems convenient to divide these cases into three general groups, to which we have arbitrarily given descriptive headings. These divisions are based in part on a concept of the mechanism producing the hypernatremia and in part on the clinical syndrome with which the hypernatremia is associated. Hypernatremia has been said to be the result of severe dehydration. In the experimental subject prolonged water deprivation will not produce significant hyperosmolarity. 2 It is necessary to add marked water loss to achieve

Harold M. Schoolman

Papers

The Unified Medical Language System: an informatics research collaboration.

Statistics in medical research.

Studies in leukemia. VII. The induction of leukemia in Swiss mice by means of cell-free filtrates of leukemic mouse brain.

Computer use in diagnosis, prognosis, and therapy.

Clinical syndromes associated with hypernatremia.