Stroke and transient ischaemic attack in over 16s: diagnosis and initial management

Summary of a study, which may be published alone or as an introduction to a full scientific paper. Algorithm (in guidelines) A flow chart of the clinical decision pathway described in the guideline, where decision points are represented with boxes, linked with arrows. Allocation concealment The process used to prevent advance knowledge of group assignment in an RCT. The allocation process should be impervious to any influence by the individual making the allocation, by being administered by someone who is not responsible for recruiting participants. Applicability How well the results of a study or NICE evidence review can answer a clinical question or be applied to the population being considered. Arm (of a clinical study) Subsection of individuals within a study who receive one particular intervention, for example placebo arm. Association Statistical relationship between 2 or more events, characteristics or other variables. The relationship may or may not be causal. Base case analysis In an economic evaluation, this is the main analysis based on the most plausible estimate of each input. In contrast, see Sensitivity analysis. Baseline The initial set of measurements at the beginning of a study (after runin period where applicable), with which subsequent results are compared. Bayesian analysis A method of statistics, where a statistic is estimated by combining established information or belief (the ‘prior’) with new evidence (the ‘likelihood’) to give a revised estimate (the ‘posterior’). Before-and-after study A study that investigates the effects of an intervention by measuring Stroke and transient ischaemic attack in over 16s: methodology FINAL (May 2019) Glossary Stroke and transient ischaemic attack in over 16s: methodology FINAL (May 2019) 35 Term Definition particular characteristics of a population both before and after taking the intervention, and assessing any change that occurs. Bias Influences on a study that can make the results look better or worse than they really are. (Bias can even make it look as if a treatment works when it does not.) Bias can occur by chance, deliberately or as a result of systematic errors in the design and execution of a study. It can also occur at different stages in the research process, for example, during the collection, analysis, interpretation, publication or review of research data. For examples see selection bias, performance bias, information bias, confounding factor, and publication bias. Blinding A way to prevent researchers, doctors and patients in a clinical trial from knowing which study group each patient is in so they cannot influence the results. The best way to do this is by sorting patients into study groups randomly. The purpose of ‘blinding’ or ‘masking’ is to protect against bias. A single-blinded study is one in which patients do not know which study group they are in (for example whether they are taking the experimental drug or a placebo). A double-blinded study is one in which neither patients nor the researchers and doctors know which study group the patients are in. A triple blind study is one in which neither the patients, clinicians or the people carrying out the statistical analysis know which treatment patients received. Carer (caregiver) Someone who looks after family, partners or friends in need of help because they are ill, frail or have a disability. Case–control study A study to find out the cause(s) of a disease or condition. This is done by comparing a group of patients who have the disease or condition (cases) with a group of people who do not have it (controls) but who are otherwise as similar as possible (in characteristics thought to be unrelated to the causes of the disease or condition). This means the researcher can look for aspects of their lives that differ to see if they may cause the condition. For example, a group of people with lung cancer might be compared with a group of people the same age that do not have lung cancer. The researcher could compare how long both groups had been exposed to tobacco smoke. Such studies are retrospective because they look back in time from the outcome to the possible causes of a disease or condition. Case series Report of a number of cases of a given disease, usually covering the course of the disease and the response to treatment. There is no comparison (control) group of patients. Clinical efficacy The extent to which an intervention is active when studied under controlled research conditions. Clinical effectiveness How well a specific test or treatment works when used in the ‘real world’ (for example, when used by a doctor with a patient at home), rather than in a carefully controlled clinical trial. Trials that assess clinical effectiveness are sometimes called management trials. Clinical effectiveness is not the same as efficacy. Clinician A healthcare professional who provides patient care. For example, a doctor, nurse or physiotherapist. Cochrane Review The Cochrane Library consists of a regularly updated collection of evidence-based medicine databases including the Cochrane Database of Systematic Reviews (reviews of randomised controlled trials prepared by the Cochrane Collaboration). Cohort study A study with 2 or more groups of people – cohorts – with similar characteristics. One group receives a treatment, is exposed to a risk Stroke and transient ischaemic attack in over 16s: methodology FINAL (May 2019) Glossary Stroke and transient ischaemic attack in over 16s: methodology FINAL (May 2019) 36 Term Definition factor or has a particular symptom and the other group does not. The study follows their progress over time and records what happens. See also observational study. Common odds ratio Cumulative odds ratio as calculated by logistic regression (shift analysis). This provides a treatment effect in the form of a common estimate of the odds ratio for improvement over considered cutpoints. This analysis relies on the assumption of an odds ratio behind any cut-off point. Comorbidity A disease or condition that someone has in addition to the health problem being studied or treated. Comparability Similarity of the groups in characteristics likely to affect the study results (such as health status or age). Concordance This is a recent term whose meaning has changed. It was initially applied to the consultation process in which doctor and patient agree therapeutic decisions that incorporate their respective views, but now includes patient support in medicine taking as well as prescribing communication. Concordance reflects social values but does not address medicine-taking and may not lead to improved adherence. Confidence interval (CI) There is always some uncertainty in research. This is because a small group of patients is studied to predict the effects of a treatment on the wider population. The confidence interval is a way of expressing how certain we are about the findings from a study, using statistics. It gives a range of results that is likely to include the ‘true’ value for the population. The CI is usually stated as ‘95% CI’, which means that the range of values has a 95 in a 100 chance of including the ‘true’ value. For example, a study may state that “based on our sample findings, we are 95% certain that the ‘true’ population blood pressure is not higher than 150 and not lower than 110”. In such a case the 95% CI would be 110 to 150. A wide confidence interval indicates a lack of certainty about the true effect of the test or treatment – often because a small group of patients has been studied. A narrow confidence interval indicates a more precise estimate (for example, if a large number of patients have been studied). Confounding factor Something that influences a study and can result in misleading findings if it is not understood or appropriately dealt with. For example, a study of heart disease may look at a group of people that exercises regularly and a group that does not exercise. If the ages of the people in the 2 groups are different, then any difference in heart disease rates between the 2 groups could be because of age rather than exercise. Therefore age is a confounding factor. Consensus methods Techniques used to reach agreement on a particular issue. Consensus methods may be used to develop NICE guidance if there is not enough good quality research evidence to give a clear answer to a question. Formal consensus methods include Delphi and nominal group techniques. Control group A group of people in a study who do not receive the treatment or test being studied. Instead, they may receive the standard treatment (sometimes called ‘usual care’) or a dummy treatment (placebo). The results for the control group are compared with those for a group receiving the treatment being tested. The aim is to check for any differences. Ideally, the people in the control group should be as similar as possible to those in the treatment group, to make it as easy as possible to detect any effects due to the treatment. Cost–benefit analysis Cost–benefit analysis is one of the tools used to carry out an Stroke and transient ischaemic attack in over 16s: methodology FINAL (May 2019) Glossary Stroke and transient ischaemic attack in over 16s: methodology FINAL (May 2019) 37 Term Definition (CBA) economic evaluation. The costs and benefits are measured using the same monetary units (for example, pounds sterling) to see whether the benefits exceed the costs. Cost–consequences analysis (CCA) Cost–consequences analysis is one of the tools used to carry out an economic evaluation. This compares the costs (such as treatment and hospital care) and the consequences (such as health outcomes) of a test or treatment with a suitable alternative. Unlike cost–benefit analysis or cost-effectiveness analysis, it does not attempt to summarise outcomes in a single measure (like the quality-adjusted life year) or in financial terms. Instead, outcomes are shown in their natural units (some of which may b