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Health Journalism Glossary

Medical Studies Glossary

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  • A priori – This term describes knowledge or assumptions made based only on what one already knows before collecting data. It’s typically used…
  • Absolute risk – The chance that something will happen within a given amount of time, stated in raw numbers. In medical studies, it’s…
  • Active vs. passive surveillance – Surveillance is the process or system for tracking cases of risk factors, medical conditions, disease cases, adverse events, etc. It’s…
  • Acute vs. chronic conditions – In the simplest terms, acute conditions are short-term while chronic conditions are long-term. However, these two ways of categorizing an…
  • Adverse event vs. side effect – Any incident that occurs following a drug, vaccine, surgery, procedure or other medical intervention. If the adverse effect was actually…
  • Attributable risk – Attributable risk is a way of measuring prevalence of a disease or condition and refers to how many cases in…
  • Attrition – Attrition is the loss of participants in a study over time. All studies have individuals who may drop out for…
  • Attrition bias – Attrition bias is the potential skewing of data/results that arises due to the attrition, or dropout rate, in a study.…
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  • Background rate – The background rate of a particular condition refers to how often it typically occurs in a particular population or in…
  • Baseline – The measurements/assessments taken at the beginning of a study before any interventions have begun represent the baseline. Outcomes assessed during…
  • Basic science – Also called basic, fundamental, or bench research, basic science involves pre-clinical research (research not performed in humans) that focuses on…
  • Bias – Biases are systematic errors in the design or reporting of medical studies that produce a false pattern of differences between…
  • Bidirectional – When two things are associated, such as a condition and an outcome, researchers often seek to find out whether one…
  • Bioavailability – Bioavailability refers to quantifying the ability of the human body to extract from a substance the nutrients or other chemicals…
  • Bioequivalence – Two different pharmaceutical products are bioequivalent if they contain the same chemical compounds in the same proportions (ideally) and are…
  • Blinding (or masking) – Blinding, also called masking, refers to concealing from participants and/or study teams who are and are not receiving an intervention…
  • Bonferroni correction – A Bonferroni correction is a calculation intended to reduce the likelihood of a false positive in study results by accounting…
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  • Case control study – This type of retrospective study design identifies a group of individuals who have already experienced a particular outcome or who…
  • Case fatality rate vs. infection fatality rate – These are two ways of measuring the fatality rate (or risk or ratio) of a particular disease. The case fatality…
  • Case study – A qualitative, descriptive study that focuses on an individual patient (a case series includes multiple individuals) and a particular condition,…
  • Clinical significance – Statistical significance measures how likely it is that a research finding occurred due to a real effect versus chance, but…
  • Comorbidity – A comorbidity refers to having two or more conditions or diseases at the same time in a person, such as…
  • Composite endpoint – When researchers measure a combination of possible clinical events in a clinical trial, they have created a composite endpoint. Composite…
  • Confidence interval – Confidence intervals are one way that researchers report statistical significance in a study. The other is the p-value. Deeper dive…
  • Conflict of interest – A set of circumstances that creates a real or perceived risk that professional judgment or actions concerning a primary interest…
  • Confounding – In observational studies, confounding variables are factors that confuse or obscure the association between a primary exposure of interest and…
  • Confounding by indication – One of the ways results can be skewed in an observational/epidemiological study is through confounding, when a factor affects both…
  • Congenital – A congenital disease, defect, abnormality, difference or other condition is one that has been present since birth. What’s important to…
  • Context – Context refers to the background information about a condition, treatment, and/or scientific question, and what the research to date has…
  • Convenience sample – A method of including participants (or data) that are convenient to reach but not randomly selected. It’s a type of…
  • Correlation vs. causation – Correlation is a relationship between two variables, and causation occurs when one of those variables has an effect on the…
  • Covariate – A covariate is a variable particular to each participant in a study (or each subject being studied, if it’s not…
  • Cross-sectional study – A kind of observational study that lacks temporality, or a relationship with time. Cross-sectional studies gather data about their participants…
  • Crossover trial – In a crossover trial, both groups are exposed to the intervention and to the placebo at different times, or both…
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  • Data and Safety Monitoring Board – Clinical trials are expected to be overseen by a Data and Safety Monitoring Board (also called Data and Safety Monitoring…
  • De novo – The term “de novo” means “of new” in Latin, but it’s used most often in research to refer to the…
  • Diagnostic test – A diagnostic test is a medical test or intervention used to establish whether a particular condition is or is not…
  • Diagnostic trial – A diagnostic clinical trial aims to identify better ways of diagnosing a condition, such as testing a new procedure, screening…
  • Disease elimination vs. eradication – Elimination of a disease occurs when the disease is no longer endemic to a particular geographical region. That is, the…
  • Dose response – “Dose response” refers to the relationship between the amount of a substance or exposure and the extent or magnitude of…
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  • Effect size – Journalists covering medical research write about effect size all the time but may not recognize that’s the name for it.…
  • Effect vs. association – An association is a statistical link or pattern between two variables, but an effect can only result if one is…
  • Effectiveness vs. efficacy – At first glance, it would seem the only difference between “effectiveness” and “efficacy” is a handful of letters. But these…
  • Embargo – A press embargo means that a journal article, research study content, announcement or other news item cannot be publicized in…
  • Endemic – Endemic refers to an organism (or phenomenon) naturally occurring in a particular geographic region without having been artificially introduced. Deeper…
  • Endpoint – The endpoint of a study is an objective outcome the researchers measure when the study concludes to determine the level…
  • Epidemiology – Epidemiology is the study of disease behavior, particularly at the population level. Epidemiology includes study of both chronic and acute…
  • Epigenetics – Epigenetics refers to the study of how changes to genes during a person’s lifetime can then be passed on in…
  • Equipoise – Equipoise is a philosophical concept that is important for reporters to understand because it underlies the bioethical justification for any…
  • Eradication – While elimination of a disease occurs when the disease is no longer endemic to a particular geographical region, eradication refers…
  • Etiology – Etiology refers to the cause of a disease or condition; most often etiology refers specifically to the biological mechanisms underpinning…
  • Exclusion criteria – These are demographic, health-related or other personal/individual factors that exclude a person from participating in a clinical study. They could…
  • Exposure – Though a common word in everyday language, exposure must be very precise in medical research, such that even entire papers…
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  • False balance (false equivalence) – This lapse in responsible reporting refers to using outliers’ voices to state opinions that contradict the facts—or the currently accepted…
  • Forest plot – A forest plot is a graphic representation of data from a meta-analysis in which the researchers need to show the…
  • Formulary – A formulary can refer to an insurance formulary or a hospital formulary. A formulary in insurance terms is the list…
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  • Gene expression – While most people understand that genes contain the DNA “instructions” for how any organism is put together and operates, those…
  • Generalizability – Generalizability refers to the extent to which findings in a particular study can be applied or extended to populations beyond…
  • Genotype – An organism’s genotype is the specific genetic material that gives rise to that organism’s characteristics. It usually refers to the…
  • Gray literature – In medical research, gray literature refers to studies that have been conducted but have not been published in a peer-reviewed…
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  • Hazard ratio – Hazard ratios, which are often abbreviated HR, are one way researchers report the relative effect of a drug, treatment, or…
  • Head-to-head trial – In a head-to-head clinical trial, researchers are not comparing an intervention against a placebo or sham control but instead are…
  • Healthy user effect – This kind of bias may be at work in studies that find an unexpected benefit associated with treatment. It refers…
  • Hill Criteria for Evaluating Observational Studies – If there’s one phrase that most reporters who cover medical studies can repeat in their sleep, it’s the caution that…
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  • ICD-9, ICD-10 and ICD-11 – The International Classification of Diseases, Ninth Revision, Tenth Revision, and Eleventh Revision, are the systems used to assign diagnoses of…
  • Idiopathic – Idiopathic describes a condition or symptom that occurs without a known cause or explanation. It’s typically used to describe conditions…
  • Impact factor – In the world of research publishing, a loose hierarchy of journals exists both overall and within individual fields. In science…
  • Imputation – In biostatistics, the results of calculations are only as good as the data used to generate them. If too much…
  • In vitro vs. in vivo (and in silico) – Experimental research involving new drugs, environmental exposures, or other chemicals or interventions will occur in one of three environments: in…
  • Inclusion criteria – These are the factors that participants in a clinical trial or other medical study must have in order to enroll…
  • Indication – This is the reason a drug, therapy, surgery or other intervention is recommended or prescribed by a doctor. A sign,…
  • Infection fatality rate – This is one of two ways of measuring the fatality rate (or risk or ratio) of a particular disease. The…
  • Informed consent – Informed consent is required for receiving any type of medical intervention, including drugs, surgeries or therapies, and for involvement in…
  • Ingelfinger rule – This refers to the New England Journal of Medicine submission policy outlined in 1969 by then-editor Franz J. Ingelfinger. He…
  • Institutional Review Boards – An institutional review board (IRB) is an administrative body that is charged with protecting the rights, privacy, and welfare of…
  • Intent-to-treat population – In a randomized, controlled trial, the intent-to-treat (ITT) population represents all the study subjects who were randomized to the different…
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  • Kaplan-Meier curves – These graphs plot the proportion of individuals surviving without an event over the study period. Time is typically depicted on…
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  • Lead time bias – Lead time bias is a common phenomenon to watch out for in screening studies, though it can be relevant in…
  • Longitudinal study – A kind of observational study that follows study participants over time. These studies take repeated measurements of the variables of…
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  • Mean – The average of numbers, calculated by adding all the numbers together and dividing the sum by the number of items.…
  • Median – The middle number (midpoint) in a series of numbers. If the median age of breast cancer diagnosis is 62, that…
  • Meta-analysis – A meta-analysis is a statistical technique for combining the results from independent studies that have all looked at the same…
  • Minimally clinically important difference (MCID) – Also called “minimally important difference” or in a slightly different form, “minimally clinically important improvement.” This term refers to the…
  • Monotherapy – Monotherapy means a person is taking only one medication to treat a particular condition. It generally refers only to the…
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  • Natural history study – These medical papers aim to explain the etiology, or origin, of a condition, its natural course and progression, and the…
  • Naturalistic study – Instead of creating an intervention or designing an observational study in which there is interaction with the participants (surveys, measurements,…
  • Negative predictive value – This is a measure of accuracy for screening tests that refers to true negatives — the probability that subjects with…
  • Nocebo effect – The opposite of the placebo effect, a nocebo effect describes side effects or increased symptoms, rather than symptom improvement, that…
  • Non-inferiority – Non-inferiority refers to a characteristic of a drug indicating that it works at least as well as another drug, often…
  • Number needed to harm – This number is similar to the number needed to treat (NNT) in the opposite direction: It is the number of…
  • Number needed to treat – The number needed to treat, or NNT, is a way to sum up treatment effect, and unlike some statistical concepts,…
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  • Objective – An objective is the reason for doing a study, what the researchers want to accomplish. The objective could be to…
  • Objective vs. outcome vs. endpoint – These three terms are often confused, particularly outcome and endpoint, which are sometimes synonyms and other times separated by a…
  • Observational study – In observational studies, researchers look for differences between exposed and unexposed groups, after people have already made their own lifestyle…
  • Off-label – When a clinician prescribes a drug for any purpose or to a population other than what the U.S. Food and…
  • Open label studies – In an open label study, both the study participants/patients and the researchers/providers know what drug or treatment the participants are…
  • Outcome – An outcome is any measure of the patient’s health, such as a score on a pain or disease severity scale,…
  • Overall survival – Overall survival refers to how long a person lives from the time they were diagnosed with a condition until the…
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  • P-hacking – P-hacking is data diving, data fishing, data mining, or any other term (dredging, snooping, etc.) that describes manipulating or rearranging…
  • Pathogenesis – In the simplest terms, pathogenesis describes how a disease begins and develops. In medical studies, researchers may discuss pathogenesis in…
  • Per-protocol population – The per-protocol population is the group of subjects in a randomized-controlled trial that most closely stuck to their treatment regimens.…
  • PET scan – Positron emission tomography, a type of medical imaging test that uses a radioactive dye that doctors can see moving through…
  • Pharmacotherapy – Use of medications to treat a condition is pharmacotherapy. Two types of pharmacotherapy are polypharmacy — use of more than…
  • Phases of Clinical Testing – New drugs and devices typically go through four, and sometimes five, phases of clinical testing. Three of these happen before…
  • Phenotype – This term refers to the physical or otherwise observable characteristics of an organism or some aspect of an organism, such…
  • Placebo effect – A placebo is a “fake” medicine or treatment intended to substitute for the real one, most commonly used for the…
  • Polypharmacy – Polypharmacy refers to the use of multiple drugs, whether to treat a single condition or to treat multiple conditions (related…
  • Positive predictive value – This is a measure of accuracy for screening tests that refers to true positives — the probability that subjects with…
  • Post hoc analysis – A post hoc analysis refers to analyzing data for reasons that differ from the reason the data was originally collected.…
  • Practice guideline – Practice guidelines are developed by a panel of experts, frequently convened as a group within a professional medical society, that…
  • Pragmatic study – Pragmatic trials have a different purpose than explanatory trials, which typically include the usual randomized controlled trials, epidemiological studies and…
  • Preprint – A preprint is a full draft of a research study shared online before it goes through the peer review process.…
  • Prevalence – Prevalence is one of two key epidemiological terms that refers to the total existing cases of a disease, injury, or…
  • Priming – This phenomenon is particularly important for psychology, sociology and other social science studies, though it can also sometimes be relevant…
  • Principal investigator – Think of a principal investigator (PI) of a clinical trial as similar to the producer of a film. The PI,…
  • Progression-free survival – Progression-free survival is an endpoint used in cancer studies. It measures how much time passes (usually measured in months) from…
  • Prospective study – A prospective study follows people forward in time. The advantage of prospective research is that researchers can pose a question…
  • Publication bias – Publication bias refers to differences between studies that get published in medical journals and those that do not. A 1991…
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  • Quality of life trial – Instead of testing how well a particular intervention treats a disease or its symptoms, a trial focused on quality of…
  • Quality-adjusted life-year – A quality-adjusted life-year, abbreviated as QALY, is a mathematically derived measurement intended to capture both quality and quantity of life.…
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  • Randomization – Trials that compare an intervention to two groups usually require randomization, where participants enrolled in the trial are randomly assigned…
  • Randomized controlled trial – A randomized controlled trial, or RCT, is a specific kind of scientific experiment in which researchers screen and recruit people,…
  • Recall bias – This type of bias refers to a research participant’s difficulty in accurately remembering information they are asked for in a…
  • Relative risk – Relative risk, usually abbreviated RR, is a comparison of risk levels between two groups in a study, usually the treatment…
  • Reporting Biases – According to the Cochrane Collaboration, reporting biases arise when the dissemination of information is skewed by the “nature and direction”…
  • Retrospective study – Retrospective studies are observational studies that look back in time. In retrospective studies, researchers start with a population that’s already…
  • Reverse causality – Also called reverse causation, reverse causality becomes a possibility when the “effect” of something could actually be its cause. For…
  • Risk – The word “risk” often connotes danger: The risk of getting cancer. But in medicine, risk is a ratio that’s used…
  • Risk ratio – A commonly used effect size used to quantify research findings is a risk ratio, another word for relative risk. The…
  • Risk-adjusted mortality rate – In the plainest terms, a risk-adjusted mortality rate means that a mortality rate has been statistically adjusted to account for…
  • Route of exposure – In talking about exposure to drugs, supplements, environmental contaminants, etc., it’s important not only to consider the dosage/concentration and duration…
  • Run-in period/phase – A run-in phase or run-in period describes the period before the trial starts when all possible study participants are given…
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  • Safety signal – A safety signal is any trend, pattern, set of symptoms or other indicator that a drug or intervention may have…
  • Scoping review – Scoping reviews are not brand new, but for reasons that are unclear, they seem to be becoming more common. Reporters…
  • Screening – Screening is a medical intervention or strategy that looks for the possible presence of a condition that has not yet…
  • Secondary endpoint – In addition to the primary endpoint reported in a study, researchers may measure and report secondary endpoints as well. These…
  • Selection bias – This bias is present in many studies and can sometimes completely invalidate the findings if the authors do not adequately…
  • Self-controlled case series – In a “controlled” study, the participants receiving an intervention are compared to a control group of participants who don’t receive…
  • Sensitivity – A way of measuring the accuracy of a screening, diagnostic, monitoring or other test in terms of how many people…
  • Sensitivity analysis – Any time researchers calculate results in an observational study, they have to make certain assumptions about what does and does…
  • Sequelae – This is a fancy word for all the effects or complications, typically long-term, that occur as a result of a…
  • Sex vs. gender – Two of the most commonly confused concepts in everyday language are sex and gender. Most often, the confusion is a…
  • Side effect – A side effect is a health symptom or condition that occurs as a result of a drug, vaccine, surgery, procedure…
  • Social desirability bias – Social desirability bias is a type of bias that can commonly occur with any type of self-reported data. It refers…
  • Specificity – A measure of a screening, diagnostic, monitoring or other lab test’s accuracy in terms of the true negative rate —…
  • Statistical significance – Statistical significance is a test that researchers apply to their results to find out if their results represent real effects…
  • Stratification – Used in the context of clinical trials, stratification refers to dividing up study participants and/or outcomes into subgroups (also called…
  • Superiority trial – Superiority trials are similar to non-inferiority trials, but instead of trying to show that one drug is no less safe…
  • Surrogate endpoints – Clinical trials often rely on surrogate endpoints to determine whether treatments work. In medicine, surrogates are biomarkers (i.e. blood pressure,…
  • Surveillance – Surveillance refers to how researchers and public health officials identify, locate, count, and track a particular disease or other condition.…
  • Surveillance bias (Detection bias) – Surveillance bias, also called detection bias, is a type of selection bias that results when one population is more likely…
  • Survival analysis – Survival analysis is a statistical calculation assessing the duration of time that passes before death occurs. While survival is one…
  • Systematic review – A systematic review is a type of study that comprehensively review all other relevant studies on a specific research question…
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  • Table 1 – In nearly every clinical trial or observational study, the researchers provide the baseline characteristics of the study participants in Table…
  • The Belmont Report – The Belmont Report lays out the ethical principles that should guide how medical/biological/behavioral research is carried out in humans.
  • Translational research – In translational or applied scientific studies, researchers use a body of scientific knowledge to solve a practical problem. For example,…
  • Treatment Emergent Adverse Event (TEAE) – A category of adverse events that can particularly occur with cancer or autoimmune condition treatments during a clinical trial is…
  • Treatment-naïve – Being treatment-naive means that an individual has not yet received any treatment for a particular condition. A treatment-naive person who…
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  • Washout period – A washout period can describe two scenarios: a) the run-in period before a study begins during which researchers are waiting…

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