WACP Primary key terms

The proportion of people diagnosed with a specified disease who die from it within a defined period. It measures severity of disease rather than how common the disease is in the population.

The proportion of a defined population that develops a disease during a limited outbreak or after a specific exposure. Often expressed as a percentage and used to identify the source of an epidemic.

The number of new cases of a disease arising in a population at risk during a stated period, divided by the person-time at risk. It reflects how rapidly new disease is occurring.

The total number of existing cases of a disease in a population at a given point or over a period, divided by the population size. It reflects disease burden and is influenced by duration of illness.

Indirect protection of susceptible people in a population when a sufficient proportion is immune, so that transmission chains break. The threshold depends on how contagious the pathogen is.

The proportion of people who truly have a condition and are correctly identified as positive by a test. A highly sensitive test is useful for ruling out disease when negative.

The proportion of people who truly do not have a condition and are correctly identified as negative by a test. A highly specific test is useful for confirming disease when positive.

The proportion of people with a positive test result who actually have the condition. It depends on disease prevalence as well as on the test's sensitivity and specificity.

The systematic testing of apparently healthy people to detect unrecognised disease early, so that treatment can improve outcome. It requires a suitable test, an accepted treatment and adequate follow-up.

Apparent improvement in survival after screening that results only from earlier diagnosis, not from delayed death. It makes screened patients seem to live longer even when screening has no real benefit.

The ratio of the risk of an outcome in an exposed group to the risk in an unexposed group. A value above one suggests increased risk associated with the exposure.

The ratio of the odds of exposure among cases to the odds of exposure among controls. It approximates relative risk when the outcome is rare and is commonly used in case-control studies.

Distortion of the estimated effect of an exposure on an outcome by a third factor that is associated with both. It can create, exaggerate or hide a true association unless adjusted for.

An experiment in which participants are allocated by chance to intervention or comparison groups. Randomisation balances known and unknown confounders, giving the strongest evidence of causal effect.

The proportional reduction in disease risk among vaccinated people compared with unvaccinated people, usually calculated as one minus the risk ratio. It is expressed as a percentage.

A national or institutional list of medicines selected because they meet priority health needs and are safe, effective and cost-effective. It guides procurement, supply and prescribing in public health systems.

The socially recognised set of rights and obligations attached to being ill, such as exemption from normal duties and the duty to seek help. It shapes how illness is interpreted and managed in a community.

A behavioural framework explaining health action by perceived susceptibility, perceived severity, perceived benefits and barriers, and cues to action. It is used to design preventive and adherence interventions.

A socially devalued mark or attribute that discredits a person or group, leading to discrimination and exclusion. In health it commonly delays help-seeking and reduces treatment adherence.

The extent to which a person's behaviour, such as taking medicines or attending appointments, matches agreed recommendations from a health worker. It is negotiated rather than simply obeyed.

Choosing medicines that are appropriate to the patient's clinical need, at an adequate dose, for an adequate duration and at acceptable cost. It avoids unnecessary or harmful polypharmacy.

The use of multiple medicines at the same time, often five or more, which increases the risk of interactions and adverse effects. It is common in older adults with several chronic conditions.

A structured clinical interview that explores the patient's ideas, concerns and expectations alongside the biomedical problem, then negotiates a shared management plan. It improves satisfaction and adherence.

A clinical feature suggesting serious underlying disease that warrants urgent investigation or referral rather than routine management. Recognising red flags prevents dangerous delay in diagnosis.

A severe, rapidly developing systemic hypersensitivity reaction with airway, breathing or circulatory compromise. It is treated immediately with intramuscular adrenaline and supportive measures.

A spectrum of acute myocardial ischaemia including unstable angina and myocardial infarction with or without ST elevation. It presents with chest pain and requires urgent ECG and troponin testing.

A cardiac muscle protein released into blood when heart muscle is damaged. Its measurement is the preferred biomarker for diagnosing myocardial infarction, interpreted with clinical features and ECG.

A clinical syndrome in which the heart cannot deliver sufficient output for the body's needs, or can do so only at raised filling pressures. It causes breathlessness, fatigue and fluid retention.

The percentage of blood in the left ventricle that is pumped out with each contraction. It is measured by echocardiography and classifies heart failure as reduced or preserved.

A metabolic emergency of insulin deficiency causing hyperglycaemia, ketonaemia and metabolic acidosis. It presents with vomiting, abdominal pain, dehydration and deep breathing, and requires fluids and insulin.

Glycated haemoglobin reflecting average blood glucose over roughly the preceding two to three months. It is used to diagnose and monitor diabetes but is unreliable in haemoglobinopathies and pregnancy.

The difference between measured cations and anions in serum, calculated as sodium minus chloride and bicarbonate. It helps classify metabolic acidosis and identify unmeasured acids such as ketones or lactate.

A blood test measuring acidity, carbon dioxide and oxygen in arterial blood, giving information on ventilation and oxygenation. It helps classify respiratory and metabolic acid-base disorders.

A laboratory test quantifying red cells, white cells and platelets along with indices such as haemoglobin and mean cell volume. It is a first-line investigation for anaemia, infection and haematological disease.

A stained smear of blood examined under a microscope to assess cell shape, size and maturity. It is used to investigate anaemia, suspected leukaemia and blood-borne parasites such as malaria.

An immediate immunoglobulin E mediated allergic reaction in which mast cells release histamine and other mediators. Examples include urticaria, asthma and anaphylaxis.

Yellow discoloration of skin and eyes in a newborn caused by raised bilirubin. It is common and usually physiological, but very high levels can cause brain injury and need urgent treatment.

Permanent neurological damage from bilirubin deposition in the basal ganglia of a newborn with severe unconjugated hyperbilirubinaemia. It causes movement disorder, hearing loss and developmental delay.

Feeding an infant with human milk, ideally exclusively for the first six months. It provides nutrition, immune protection and bonding, and reduces diarrhoeal and respiratory illness.

A plotted reference of weight, length or head circumference against age used to detect faltering growth or obesity. Serial measurements are more informative than a single point.

A life-threatening state of nutritional deficiency identified by very low weight-for-height, mid-upper arm circumference or bilateral oedema. It requires careful therapeutic feeding and treatment of infection.

A skill such as sitting, walking or speaking that most children acquire within an expected age range. Delay in milestones prompts assessment for developmental or neurological disorder.

A mood disorder with persistent low mood or loss of interest plus symptoms such as disturbed sleep, fatigue and poor concentration for at least two weeks, causing functional impairment.

A structured inquiry into thoughts, plans, intent, means and protective factors in a person who may harm themselves. It guides immediate safety planning and level of care.

A nine-item self-report questionnaire scoring the frequency of depressive symptoms over two weeks. It supports detection and monitoring of depression but does not replace clinical assessment.

A mental state with loss of contact with reality, shown by hallucinations, delusions or disorganised thinking. It requires urgent assessment to exclude organic causes and to start treatment.

An acute, fluctuating disturbance of attention and awareness usually caused by physical illness, drugs or withdrawal. It is a medical emergency and is often mistaken for psychiatric illness.