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Glossary of Medical Writing Terms

Welcome to our Medical Writing Glossary! From common acronyms to complex scientific terms, we're here to demystify the language of medical writing.




Adverse Drug Reaction. An undesired harmful effect resulting from a medication or other intervention such as surgery or a medical device.


Adverse Event. Any untoward medical occurrence in a patient administered a drug, not necessarily causally related.


Complete Response. The complete disappearance of all signs of a disease or condition as confirmed by medical assessment or diagnostic tests, indicating successful and comprehensive treatment.


Data and Safety Monitoring Board. An independent committee responsible for reviewing and evaluating the safety and efficacy data from a clinical trial to ensure participant safety and data integrity.


European Quality of Life Five Dimension. A standardised instrument used to measure health-related quality of life developed by the EuroQol Group, consisting of five dimensions: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression, each with three levels of severity, providing a descriptive profile and a single index value for health status assessment.


Health Economics and Outcomes Research. A field of study that assesses the value of healthcare interventions by analysing their economic impact, effectiveness, safety, and patient outcomes.


Health-Related Quality of Life. An individual's perceived physical, mental, emotional, and social wellbeing related to their health status, encompassing factors such as functional status, symptom burden, psychological wellbeing, and overall satisfaction with life, influenced by both disease and treatment effects


Intramuscular. Injection of medication into a muscle.


Institutional Review Board. A committee responsible for ensuring that research involving human subjects adheres to ethical standards and regulatory requirements.


Intravenous. Administration of medication or fluids directly into a vein.

NCT no.

The unique identification code given to each clinical study upon registration at The format is "NCT" followed by an 8-digit number.


Open Label Extension. Participants who completed the original trial continue receiving the investigational treatment with both the participant and researchers aware of the treatment being administered, aiming to gather long-term safety and efficacy data.


Over-The-Counter. Refers to medicines that can be bought without a prescription.


By mouth. Oral administration of medication


As needed. Medication taken only when needed for symptom relief.


Patient Reported Outcomes. Health outcomes directly reported by patients about their symptoms, quality of life, functional status, etc.


Quality-Adjusted Life-Year. A measure used in health economics to quantify the value of healthcare interventions by combining both the quantity and quality of life gained from a particular treatment or intervention.


Partial Response. A medical condition or treatment outcome where there is an improvement in symptoms or disease status, but it is not complete or total.


Randomised Controlled Trial. The most rigorous type of clinical research with randomly assigned groups.


Response Evaluation Criteria in Solid Tumors. Provides standardised guidelines for measuring tumour response to treatment in oncology trials, aiding in assessing treatment effectiveness and facilitating comparison across studies.


Serious Adverse Event. An adverse event that results in death, is life-threatening, requires hospitalisation or leads to disability.


Subcutaneous. The tissue layer located just beneath the skin. Medications administered SC are injected into this layer using a needle, allowing for the gradual absorption of the medication into the bloodstream.


Treatment-Emergent Adverse Event. An undesirable medical occurrence or side effect that arises during or after the administration of a treatment, such as a medication or medical intervention, that was not present prior to the treatment.


Treatment-Emergent Adverse Event. Any negative or undesirable medical occurrence experienced by a patient that is determined to be related to the treatment they are undergoing, such as a medication, therapy, or medical intervention.




Acute Lymphoblastic Leukaemia. A rapidly progressing cancer of the blood and bone marrow characterised by the overproduction of immature lymphocyte cells, primarily affecting children.


Acute Kidney Injury. A sudden and often reversible decline in kidney function caused by factors such as decreased blood flow, kidney tissue damage, or urinary tract obstruction, requiring prompt diagnosis and treatment to prevent complications and potential progression to CKD.


Age-Related Macular Degeneration. A progressive eye condition that primarily affects older adults and leads to deterioration of the macula, the central part of the retina responsible for sharp, central vision. This can result in blurred or distorted vision, making it difficult to perform tasks such as reading or recognising faces.


Acute Myeloid Leukaemia. A fast-growing cancer of the blood and bone marrow characterised by the rapid proliferation of abnormal myeloid cells.


Biochemical Recurrence. A rise in PSA levels after primary treatment of prostate cancer, indicating the potential presence of residual or recurrent cancer cells, even though there may be no visible evidence of disease on imaging studies.


Cerebral Adrenoleukodystrophy. A rare genetic disorder causing the accumulation of fatty acids in the brain, leading to progressive neurological degeneration.


Chronic Inflammatory Demyelinating Polyneuropathy. A rare autoimmune disorder characterised by progressive weakness and sensory disturbances due to inflammation and damage to the peripheral nerves' myelin sheath. Symptoms may include muscle weakness, numbness, tingling, and impaired coordination, and the condition typically presents gradually and worsens over time. Treatment often involves immunosuppressive therapy to reduce inflammation and manage symptoms.


Chronic Kidney Disease. A long-term condition where the kidneys gradually lose their function over time, leading to a buildup of waste and fluid in the body. CKD is typically characterised by reduced kidney function, indicated by a decreased glomerular filtration rate (GFR) or markers of kidney damage, and it can progress through stages of increasing severity. Common causes include diabetes, high blood pressure, and certain kidney diseases.


Chronic Lymphocytic Leukaemia. A slowly progressing cancer of the blood and bone marrow characterised by the overproduction of abnormal lymphocytes, primarily affecting older adults.


Chronic Myeloid Leukaemia. A cancer of the bone marrow marked by excessive production of immature myeloid cells, progressing through chronic, accelerated, and blast crisis phases if untreated.


Cytomegalovirus. A common virus belonging to the herpesvirus family. It can cause mild or no symptoms in healthy individuals but can lead to severe complications in people with weakened immune systems, such as newborns, transplant recipients, and those with HIV/AIDS.


Chronic Obstructive Pulmonary Disease. A chronic inflammatory lung disease that obstructs airflow from the lungs.


Complicated Intra-Abdominal Infections. Infections affecting organs or structures within the abdomen that require advanced medical intervention such as antibiotics and sometimes surgery due to their complexity or severity.


Complicated Skin and Soft Tissue Infections. Infections that involve deeper layers of the skin, such as cellulitis, necrotising fasciitis, and infected ulcers, and may extend to surrounding soft tissues. They often require more extensive medical intervention, such as antibiotics, surgical debridement, or drainage, due to their complexity or severity compared to uncomplicated skin and soft tissue infections.


Complicated Urinary Tract Infections. Infections of the urinary tract that involve additional complications, such as structural abnormalities, urinary tract obstruction, or antibiotic resistance, necessitating more complex medical management.


Diffuse Large B cell Lymphoma. An aggressive type of non-Hodgkin lymphoma characterised by rapidly growing masses of abnormal B-cells in lymph nodes or other organs.


Diabetes Mellitus. A group of diseases that result in too much sugar in the blood.


Diabetic Macular Oedema. A complication of diabetes that occurs when fluid accumulates in the macula, the central part of the retina responsible for sharp vision, leading to swelling and distortion of vision.


Dravet Syndrome. A rare and severe form of epilepsy that typically begins in infancy, characterised by prolonged and recurrent seizures, often triggered by fever or hot temperatures, along with developmental delays, cognitive impairment, and other neurological and behavioural issues.


Deep Vein Thrombosis. The formation of blood clots in the deep veins, typically in the legs, which can lead to serious complications such as pulmonary embolism.


End-Stage Renal Disease. The final stage of CKD where kidney function is severely impaired, usually less than 10-15% of normal. At this stage, the kidneys are no longer able to function well enough to meet the body's needs, requiring kidney replacement therapy such as dialysis or kidney transplantation for survival.


Follicular Lymphoma. A slow-growing type of non-Hodgkin lymphoma characterised by the abnormal proliferation of B-cells within lymph nodes, often forming small, rounded structures called follicles.


Guillain–Barré syndrome. A rare neurological disorder where the body's immune system mistakenly attacks the peripheral nervous system, leading to muscle weakness, paralysis, and potentially life-threatening complications.


Heart Failure. A medical condition characterised by the heart's inability to pump blood effectively, leading to symptoms such as shortness of breath, fatigue, and fluid retention, often resulting from underlying cardiovascular diseases or other health conditions


Human Papillomavirus. A group of viruses that infect the skin and mucous membranes of humans. Some types of HPV can cause warts, while others are sexually transmitted and can lead to various cancers, including cervical, anal, penile, and oropharyngeal cancers.


Localised prostate cancer. Cancerous growth confined within the prostate gland that has not spread to other parts of the body, typically presenting with a favourable prognosis.


Lennox-Gastaut Syndrome. A severe form of epilepsy that typically begins in childhood and is characterised by multiple types of seizures, including tonic (stiffening), atonic (drop attacks), and atypical absence seizures, along with intellectual disability and abnormal EEG patterns.


Mantle Cell Lymphoma. A subtype of non-Hodgkin lymphoma characterised by the abnormal proliferation of B-cells originating from the mantle zone of the lymph node, typically presenting as aggressive disease with a tendency to relapse.


Myocardial Infarction. Commonly known as a heart attack.


Metastatic Castration-Resistant Prostate Cancer. Prostate cancer that has spread to other parts of the body and is no longer responsive to hormone therapy.


Metastatic Hormone-Sensitive Prostate Cancer. Prostate cancer that has spread beyond the prostate gland to other parts of the body and continues to respond to hormone therapy. It is typically treated with hormone therapy along with other treatments such as chemotherapy or targeted therapy.


Mucopolysaccharidosis Type I. Also known as Hurler syndrome, this is a rare genetic disorder caused by the deficiency of the enzyme alpha-L-iduronidase, leading to the accumulation of complex sugars called glycosaminoglycans (GAGs) in various tissues and organs of the body. MPS I can result in a range of symptoms, including skeletal abnormalities, organ enlargement, developmental delays, and progressive neurological deterioration.


Multiple Sclerosis. A chronic neurological condition characterised by inflammation, demyelination, and scarring in the CNS. This can lead to a wide range of symptoms, including fatigue, impaired mobility, muscle weakness, numbness or tingling, and problems with coordination and vision. The severity and progression of MS can vary greatly among individuals.


Non-Metastatic Castration-Resistant Prostate Cancer. A stage of prostate cancer where the disease has become resistant to hormonal therapies but has not yet spread to other parts of the body, typically requiring close monitoring and potentially alternative treatments to delay or prevent the onset of metastasis.


Neuromyelitis Optica Spectrum Disorder. A rare autoimmune disease primarily affecting the optic nerves and spinal cord. It is characterised by recurrent episodes of optic neuritis and myelitis, leading to vision loss, weakness, sensory disturbances, and other neurological symptoms.


Non-Small Cell Lung Cancer. The most common type of lung cancer, comprising various subtypes such as adenocarcinoma, squamous cell carcinoma, and large cell carcinoma, with distinct characteristics and treatment approaches compared to small cell lung cancer (SCLC).


Paroxysmal Nocturnal Haemoglobinuria. A rare and acquired blood disorder characterised by the abnormal breakdown of red blood cells (haemolysis), leading to symptoms such as dark urine, fatigue, shortness of breath, abdominal pain, and blood clots. It is caused by a mutation in the PIG-A gene, resulting in the deficiency of certain proteins on the surface of blood cells, making them susceptible to destruction by the immune system.


Transfusion-Dependent Thalassemia. A severe form of thalassemia, a genetic blood disorder characterised by reduced production of haemoglobin. In TDT, the affected individual requires regular blood transfusions to maintain adequate haemoglobin levels and prevent complications associated with anaemia.


Transient Ischaemic Attack. Often called a mini-stroke.


Tuberous Sclerosis Complex. A rare genetic disorder characterised by the growth of benign tumours in various organs of the body, including the brain, kidneys, heart, lungs, skin, and eyes, often leading to seizures, developmental delays, intellectual disability, skin abnormalities, and other health problems.


Thrombotic Thrombocytopenic Purpura. A rare and serious blood disorder characterised by blood clots forming in small blood vessels throughout the body. This leads to a low platelet count (thrombocytopenia) and can cause symptoms such as bruising, purpura, neurological abnormalities, fever, and kidney problems. TTP is often caused by a deficiency in the enzyme ADAMTS13, which is responsible for breaking down large von Willebrand factor proteins.


Uncomplicated Urinary Tract Infections. Infections of the urinary tract typically limited to the bladder and not associated with any structural abnormalities or systemic illness.


Venous Thromboembolism. A medical condition encompassing deep vein thrombosis (DVT) and pulmonary embolism (PE), which involve the formation of blood clots in veins, often leading to serious health risks.




Angiotensin-Converting Enzyme Inhibitor. Lowers blood pressure by inhibiting a specific enzyme.


Angiotensin II Receptor Blocker. Another type of medication used to lower blood pressure.

GLP-1 agonists

Glucagon-Like Peptide-1 Receptor Agonists. Medications used to treat type 2 diabetes by stimulating insulin secretion and reducing glucose production.


Nonsteroidal Anti-inflammatory Drug. Pain reliever and anti-inflammatory medication.

SGLT-2 inhibitors

Sodium-Glucose Cotransporter-2 Inhibitors. Medications used to treat type 2 diabetes by blocking the reabsorption of glucose in the kidneys, leading to increased glucose excretion in the urine.


Selective Serotonin Reuptake Inhibitor. Antidepressant medication that increases serotonin levels in the brain.


Tumor Necrosis Factor-alpha. A protein involved in inflammation and the immune response.




Body Mass Index. A measure that uses height and weight to determine if a person’s weight is healthy.


Blood Pressure. The pressure of the blood in the circulatory system.


Blood Urea Nitrogen. The amount of urea nitrogen found in blood. The liver produces urea in the urea cycle as a waste product of the digestion of protein.


Complete Blood Count. Analyses blood cell levels to identify potential health issues.


Computed Tomography. Uses X-rays to create detailed cross-sectional images of the body.


Dual-Energy X-ray Absorptiometry. Measures bone density to diagnose osteoporosis.


Electrocardiogram. Records electrical activity of the heart to diagnose problems.


Electroencephalogram. Measures electrical activity of the brain to assess neurological function.


Lactate Dehydrogenase. LDH levels are important as they indicate tissue damage or disease, aiding in diagnosis and treatment monitoring for conditions like heart attacks, liver disease, muscle injury, and certain cancers.


Liver Function Tests. A group of blood tests that assess the health and function of the liver, including levels of enzymes, proteins, and bilirubin.


Magnetic Resonance Imaging. Creates detailed images of organs and tissues using magnetic fields.


Positron Emission Tomography. Measures metabolic activity in the body to diagnose diseases.




Association of the British Pharmaceutical Industry. The main trade body and advocacy organisation representing research-based pharmaceutical companies in the United Kingdom


Centers for Disease Control and Prevention. Tracks and prevents infectious diseases.


European Federation of Pharmaceutical Industries and Associations. A trade association representing the pharmaceutical industry in Europe, advocating for policies that support innovation, research, and patient access to medicines while promoting ethical business practices and regulatory compliance.


European Medicines Agency. It is an agency of the EU responsible for the evaluation, supervision, and regulation of medicinal products for human and veterinary use.


US Food and Drug Administration. Regulates drugs, medical devices, and food safety.


Medicines and Healthcare products Regulatory Agency. It is the regulatory body responsible for regulating medicines, medical devices, and blood components for transfusion in the UK.


Medical Research Council. A publicly funded organisation in the UK that supports and funds medical research, aiming to improve human health and advance medical knowledge through scientific research.


National Institute for Health and Care Excellence. It provides national guidance and advice to improve health and social care.


National Institutes of Health. Funds and conducts medical research.


Prescription Medicines Code of Practice Authority. The regulatory body responsible for overseeing the application of the ABPI Code of Practice for the Pharmaceutical Industry.


World Health Organization. Leads global health efforts and sets standards.



Analysis of Variance. Statistical test to compare means of multiple groups.


Absolute Risk Reduction. The difference in the risk of an outcome between two groups in a clinical trial.


Area Under the Curve. A measure of how much drug reaches a person’s bloodstream within a specific time period after a dose is administered.


Confidence Interval. The range of values likely to contain the true population parameter.


Intention-to-Treat. The principle that trial subjects are analysed based on their randomised group, regardless of adherence.


Least Squares. A method used in statistics to find the best-fitting line or curve through a set of data points by minimising the sum of the squares of the differences between the observed and predicted values, often used in regression analysis to estimate the parameters of a model.


Mixed-Effect Model for Repeated Measures. A statistical analysis technique that accounts for both within-subject correlations and between-subject variations, allowing for the examination of longitudinal or repeated measurements while accommodating individual differences and potential dependencies among observations.


Number Needed to Treat. The number of people who need to take a medication to prevent one event.

ROC curve

Receiver Operating Characteristic curve. A graphical plot that illustrates the performance of a binary classifier system across different discrimination thresholds by plotting the true positive rate (sensitivity) against the false positive rate (1-specificity), commonly used in diagnostic testing to evaluate the trade-off between sensitivity and specificity.


Relative Risk. Compares the risk of an event in one group to another.


Standard Deviation. A measure of how spread out a set of data is.


Standard Error. A measure of the variability or precision of a sample statistic, representing the standard deviation of the sampling distribution of that statistic.



Abbreviated Prescribing Information. A concise summary of key details about a medication, including its indications, dosage, contraindications, warnings, and adverse reactions, intended to provide essential prescribing guidance to HCPs.


High-Density Lipoprotein. Often referred to as ‘good’ cholesterol.


International Classification of Diseases, 10th Revision. Standardised codes for diagnoses.


Low-Density Lipoprotein. Often referred to as ‘bad’ cholesterol.

Last updated: February 2024.

For more plain-language descriptions of medical terms, visit the EMA Medical Terms Simplifier.
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