Clinical research in the context of Level of evidence

Neurology (from Greek: νεῦρον (neûron), "string, nerve" and the suffix -logia, "study of") is the branch of medicine dealing with the diagnosis and treatment of all categories of conditions and disease involving the nervous system, which comprises the brain, the spinal cord and the peripheral nerves. Neurological practice relies heavily on the field of neuroscience, the scientific study of the nervous system, using various techniques of neurotherapy.

A neurologist is a physician specializing in neurology and trained to investigate, diagnose and treat neurological disorders. Neurologists diagnose and treat myriad neurologic conditions, including stroke, epilepsy, movement disorders such as Parkinson's disease, brain infections, autoimmune neurologic disorders such as multiple sclerosis, sleep disorders, brain injury, headache disorders like migraine, tumors of the brain and dementias such as Alzheimer's disease. Neurologists may also have roles in clinical research, clinical trials, and basic or translational research. Neurology is a nonsurgical specialty, its corresponding surgical specialty is neurosurgery.

Medical research (or biomedical research), also known as health research, refers to the process of using scientific methods with the aim to produce knowledge about human diseases, the prevention and treatment of illness, and the promotion of health.

Medical research encompasses a wide array of research, extending from "basic research" (also called bench science or bench research), – involving fundamental scientific principles that may apply to a preclinical understanding – to clinical research, which involves studies of people who may be subjects in clinical trials. Within this spectrum is applied research, or translational research, conducted to expand knowledge in the field of medicine.

Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and determinants of health and disease conditions in a defined population, and application of this knowledge to prevent diseases.

It is a cornerstone of public health, and shapes policy decisions and evidence-based practice by identifying risk factors for disease and targets for preventive healthcare. Epidemiologists help with study design, collection, and statistical analysis of data, amend interpretation and dissemination of results (including peer review and occasional systematic review). Epidemiology has helped develop methodology used in clinical research, public health studies, and, to a lesser extent, basic research in the biological sciences.

Evolutionary linguistics or Darwinian linguistics is a sociobiological approach to the study of language. Evolutionary linguists consider linguistics as a subfield of sociobiology and evolutionary psychology. The approach is also closely linked with evolutionary anthropology, cognitive linguistics and biolinguistics. Studying languages as the products of nature, it is interested in the biological origin and development of language. Evolutionary linguistics is contrasted with humanistic approaches, especially structural linguistics.

A main challenge in this research is the lack of empirical data: there are no archaeological traces of early human language. Computational biological modelling and clinical research with artificial languages have been employed to fill in gaps of knowledge. Although biology is understood to shape the brain, which processes language, there is no clear link between biology and specific human language structures or linguistic universals.

Experimental data in science and engineering is data produced by a measurement, test method, experimental design or quasi-experimental design. In clinical research any data produced are the result of a clinical trial. Experimental data may be qualitative or quantitative, each being appropriate for different investigations.

Generally speaking, qualitative data are considered more descriptive and can be subjective in comparison to having a continuous measurement scale that produces numbers. Whereas quantitative data are gathered in a manner that is normally experimentally repeatable, qualitative information is usually more closely related to phenomenal meaning and is, therefore, subject to interpretation by individual observers.

Random assignment or random placement is an experimental technique for assigning human participants or animal subjects to different groups in an experiment (e.g., a treatment group versus a control group) using randomization, such as by a chance procedure (e.g., flipping a coin) or a random number generator. This ensures that each participant or subject has an equal chance of being placed in any group. Random assignment of participants helps to ensure that any differences between and within the groups are not systematic at the outset of the experiment. Thus, any differences between groups recorded at the end of the experiment can be more confidently attributed to the experimental procedures or treatment.

Random assignment, blinding, and controlling are key aspects of the design of experiments because they help ensure that the results are not spurious or deceptive via confounding. This is why randomized controlled trials are vital in clinical research, especially ones that can be double-blinded and placebo-controlled.

The International Classification of Headache Disorders (ICHD) is a detailed hierarchical classification of all headache-related disorders published by the International Headache Society. It is considered the official classification of headaches by the World Health Organization, and, in 1992, was incorporated into the 10th edition of their International Classification of Diseases (ICD-10). Each class of headache contains explicit diagnostic criteria—meaning that the criteria include quantities rather than vague terms like several or usually—that are based on clinical and laboratory observations.

The ICHD was first published in 1988 (now known as the ICHD-1). A second version, the ICHD-2, was published in 2004. The most current version, ICHD-3, was published in 2018.

A hierarchy of evidence, comprising levels of evidence (LOEs), that is, evidence levels (ELs), is a heuristic used to rank the relative strength of results obtained from experimental research, especially medical research. There is broad agreement on the relative strength of large-scale, epidemiological studies. More than 80 different hierarchies have been proposed for assessing medical evidence. The design of the study (such as a case report for an individual patient or a blinded randomized controlled trial) and the endpoints measured (such as survival or quality of life) affect the strength of the evidence. In clinical research, the best evidence for treatment efficacy is mainly from meta-analyses of randomized controlled trials (RCTs) and the least relevant evidence is expert opinion, including consensus of such. Systematic reviews of completed, high-quality randomized controlled trials – such as those published by the Cochrane Collaboration – rank the same as systematic review of completed high-quality observational studies in regard to the study of side effects. Evidence hierarchies are often applied in evidence-based practices and are integral to evidence-based medicine (EBM).

Oncology, from Ancient Greek ὄγκος (ónkos), meaning "tumor, bulk", and λόγος (lógos), meaning "study", is a branch of medicine that deals with the study, treatment, diagnosis, and prevention of cancer. A medical professional who practices oncology is an oncologist.

Oncology is focused on the diagnosis of cancer in a person, therapy (e.g., surgery, chemotherapy, radiotherapy and other modalities), monitoring of people after treatment, palliative care for people with advanced-stage cancers, ethical questions surrounding cancer care, screening of people who may have cancer, and the study of cancer treatments through clinical research.

A medical writer, also referred to as medical communicator, is a person who applies the principles of clinical research in developing clinical trial documents that effectively and clearly describe research results, product use, and other medical information.Medical writing is a form of technical writing closely associated with scientific technical writing. A medical writer is often required by regulation or organization to follow the five modules of the Common Technical Document (CTD). The CTD format is most commonly used to write white papers. Medical writers ensure these documents comply with regulatory, journal, or other guidelines in terms of content, format, and structure.

Medical writing as a function became established in the pharmaceutical, medical device industry and Contract Research Organizations (CROs) because the industry recognized that it requires special skill to produce well-structured documents that present information clearly and concisely. All new drugs go through the increasingly complex process of clinical trials and regulatory procedures that lead to market approval. This demand for the clear articulation of medical science, drives the demand for well written, standards-compliant documents that medical professionals can easily and quickly read and understand. Similarly, medical institutions engage in translational research, and some medical writers have experience offering writing support to the principal investigators for grant applications and specialized publications.

An honest broker is an entity that keeps sets of private information but distributes parts of those sets to other entities who should not have access to the entire set. Honest brokers often work in clinical research with biological specimens; in that case, donors of specimens allow researchers to do research on those specimens, but typically want their specimen de-identified by having protected health information separated from it. The honest broker would keep both the specimen and associated protected health information, but only allow researchers to have access to the specimen without the protected health information.

In drug development and production, good clinical practice (GCP) is an international quality standard, which governments can then transpose into regulations for clinical trials involving human subjects. GCP follows the International Council for Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH), and enforces tight guidelines on ethical aspects of clinical research.

High standards are required in terms of comprehensive documentation for the clinical protocol, record keeping, training, and facilities, including computers and software. Quality assurance and inspections ensure that these standards are achieved. GCP aims to ensure that the studies are scientifically authentic and that the clinical properties of the investigational product are properly documented.

A fad diet is a diet that is popular, generally only for a short time, similar to fads in fashion, without being a standard scientific dietary recommendation. They often make unreasonable claims for fast weight loss or health improvements, and as such are often considered a type of pseudoscientific diet. Fad diets are usually not supported by clinical research and their health recommendations are not peer-reviewed, thus they often make unsubstantiated statements about health and disease.

Generally, fad diets promise an assortment of desired changes requiring little effort, thus attracting the interest of consumers uneducated about whole-diet, whole-lifestyle changes necessary for sustainable health benefits. Fad diets are often promoted with exaggerated claims, such as rapid weight loss of more than 1 kg/week, improving health by "detoxification", or even more dangerous claims achieved through highly restrictive and nutritionally unbalanced food choices leading to malnutrition or even eating non-food items such as cotton wool. Highly restrictive fad diets should be avoided. At best, fad diets may offer novel and engaging ways to reduce caloric intake, but at worst they may be unsustainable, medically unsuitable to the individual, or even dangerous. Dietitian advice should be preferred before attempting any diet.