Objective: Medical decision-making is often uncertain. The positive predictive value (PPV) and negative predictive value (NPV) are conditional probabilities characterizing diagnostic tests and assessing diagnostic interventions in clinical medicine and epidemiology. The PPV is the probability that a patient has a specified disease, given a positive test result for that disease. The NPV is the probability that a patient does not have the disease, given a negative test result for that disease. Both values depend on disease incidence or prevalence, which may be highly uncertain for unfamiliar diseases, epidemics, etc. Probability distributions for this uncertainty are usually unavailable. We develop a non-probabilistic method for interpreting PPV and NPV with uncertain prevalence.
Methods: Uncertainty in PPV and NPV is managed with the non-probabilistic concept of robustness in info-gap theory. Robustness of PPV or NPV estimates is the greatest uncertainty (in prevalence) at which the estimate’s error is acceptable.
Results: Four properties are demonstrated. Zeroing: best estimates of PPV or NPV have no robustness to uncertain prevalence; best estimates are unreliable for interpreting diagnostic tests. Trade-off: robustness increases as error increases; this trade-off identifies robustly reliable error in PPV or NPV. Preference reversal: sometimes sub-optimal PPV or NPV estimates are more robust to uncertain incidence or prevalence than optimal estimates, motivating reversal of preference from the putative optimum to the sub-optimal estimate. Trade-off between specificity and robustness to uncertainty: the robustness increases as test-specificity decreases. These four properties underlie the interpretation of PPV and NPV.
Conclusions: The PPV and NPV assess diagnostic tests, but are sensitive to lack of knowledge that generates non-probabilistic uncertain prevalence and must be supplemented with robustness analysis. When uncertainties abound, as with unfamiliar diseases, assessing robustness is critical to avoiding erroneous decisions.
At the time of writing, in July 2020, the COVID-19 pandemic has already inflicted dramatic international restrictions, including airports closing and limiting international travel. It has been suggested that re-opening of airports should involve and even rely on testing travelers for COVID-19. This paper discusses the methodology of estimating the detection and diagnostic accuracy of COVID-19 tests. It explains the clear distinction between the technical characteristics of the tests, the detection measures, and the diagnostic measures that have clinical and public health implications. It demonstrates the importance of the prevalence of COVID-19 in terms of determining the ability of a test to yield a diagnosis. We explain the methodology of evaluating diagnostic tests, using the predictive summary index (PSI), and the minimum number of tests that need to be performed in order to correctly diagnose one person, which is estimated by 1/PSI. In a population with low prevalence, even a high-sensitivity test may lead to a high percentage of false positive diagnoses, resulting in the need for multiple high-cost tests to achieve a correct diagnosis. Thus, basing a policy for opening airports on diagnostic testing, even with the best test for COVID-19, has some limits.
The outbreak of coronavirus disease 2019 (COVID-19) in Italy, the first Western country hit by the pandemic, seriously impacted the Italian healthcare system and social and economic environment. This perspective piece focuses on the main challenges faced by Italian hospital managements: hospital overcrowding; the need for urgent reorganization of the country’s healthcare systems; the lack of data regarding COVID-19 diagnostics, clinical course, and effective treatment; individual and collective consequences of the crisis; and the importance of disease containment measures and early treatment strategies.
Surprisingly, an utterly imaginative “portrait” has become synonymous with Maimonides forever. How and when did this particular portrait become associated with Maimonides? This and many other intriguing questions regarding this portrait are systematically addressed, and its origins, possible inspiration, and hidden objectives are revealed.
Moritz Schiff was one of the pioneers of modern experimental physiology. His involvement in the liberal movement forced him out of Germany, and, because of his adherence to proper physiological research, he had to flee Italy, his first refuge. The number and importance of his contributions are outstanding. The aim of this paper is to raise interest in his biography and to present a yet unreported field of research that is regarded as the root of functional imaging of the brain.
On May 28, 2014, colleagues from the Mayo Clinic visited Rambam Health Care Campus to gather and exchange ideas and knowledge. American and Israeli caregivers and scientists shared with each other the daily challenges of their practice in many and varied settings. This issue is dedicated to the presentations given and the collaborative efforts we are building as a result of that visit. We hope this issue will serve as an example of the fruitfulness of international collaboration to enhance and propagate medical knowledge worldwide.
I am pleased to announce that the winner of the 2018 Maimonides Best Published Original Research Prize is Dr. Louise Kezerle, the first author of the paper entitled, “A Population-based Study of Peripartum Cardiomyopathy in Southern Israel: Are Bedouin Women a New High-risk Group?” with co-authors Iftach M. Sagy, Leah Shalev, Offer Erez, and Leonid Barski.
The increasing medicinal use of cannabis during recent years has largely overlooked children and pregnant women due to litigious and ethical concerns. However, over the last few years medicine has observed increasing numbers of children treated with cannabis for autism spectrum disorder (ASD) and fetal alcohol spectrum disorder (FASD), and pregnant women treated for hyperemesis gravidarum (HG). This review provides an account of major findings discovered through this research. Specifically, cannabis may offer therapeutic advantages to behavioral symptoms of autism spectrum disorder and fetal alcohol spectrum disorder, and to the severe nausea and vomiting in hyperemesis gravidarum. The use of medical cannabis in children and pregnant women should be further discussed and researched in this patient population.
To the Editor,
We read with great interest the retrospective article of Tekin and Engin that investigated the prognostic significance of the ratio of mean platelet volume (MPV) to platelet count ratio (MPVPCR) in patients with Crimean-Congo hemorrhagic fever (CCHF). The authors found that MPVPCR was significantly lower in survivors than in non-survivors, and there-fore they suggested that this ratio could be used as a mortality marker. We think there are other factors that might have affected the results of this study.
