GCPS Primary Exam key terms

The proportion of people who truly have a disease and are correctly identified by a test as positive. It measures how well a test detects disease and is calculated as true positives divided by all people with the disease.

The proportion of people without the disease who are correctly identified by a test as negative. High specificity means few false positives, so a positive result strongly supports the diagnosis when the test is used in the right population.

The probability that a person with a positive test result actually has the disease. Unlike sensitivity, it depends heavily on disease prevalence, so the same test performs differently in high-risk and low-risk populations.

The number of patients who must receive a treatment for one additional patient to benefit. It is the reciprocal of the absolute risk reduction, and a smaller value indicates a more effective intervention.

The arithmetic difference in event rates between a control group and a treated group, expressed as a percentage or proportion. It reflects the true clinical benefit better than relative risk reduction, which can appear large when baseline risk is low.

A range of values within which the true population estimate is likely to lie, usually stated at 95 percent confidence. A narrow interval implies a precise estimate, while an interval crossing no effect suggests the finding may be due to chance.

A measure of association comparing the odds of exposure among cases with the odds of exposure among controls. It is commonly used in case-control studies and approximates the risk ratio when the disease is rare.

An apparent improvement in survival that occurs only because screening detects disease earlier, lengthening the time a person is known to have the disease without actually postponing death. It explains why survival statistics can mislead in screening programmes.

The study of what the body does to a drug, covering absorption, distribution, metabolism and excretion. These processes determine the concentration of drug at its site of action over time and guide dosing intervals and route selection.

The apparent volume into which a drug would need to spread to produce its observed plasma concentration, calculated as dose divided by plasma concentration. A large value suggests extensive tissue uptake rather than confinement to blood.

The volume of plasma from which a drug is completely removed per unit time. It determines the maintenance dose needed to achieve a steady-state concentration and is influenced by hepatic and renal function.

The time required for the plasma concentration of a drug to fall by half. It guides dosing frequency and predicts how long a drug persists after stopping, with roughly four to five half-lives needed to reach steady state or elimination.

The breakdown of an orally administered drug in the gut wall or liver before it reaches the systemic circulation. Drugs with extensive first-pass metabolism have low oral bioavailability and may require higher oral doses or an alternative route.

The fraction of an administered dose of drug that reaches the systemic circulation unchanged. Intravenous administration is defined as complete, while oral bioavailability is reduced by incomplete absorption and first-pass metabolism.

The ratio between the dose that produces toxicity and the dose that produces the desired effect. A narrow index, as with digoxin or warfarin, means small dose changes or interactions can cause harm, so monitoring is required.

The physiological adjustment of carbon dioxide or bicarbonate to limit the pH change caused by a primary respiratory or metabolic disorder. Respiratory compensation is rapid, whereas renal compensation develops over hours to days and is limited in magnitude.

The difference between measured cations and measured anions in serum, calculated as sodium minus chloride minus bicarbonate. An elevated gap suggests accumulation of unmeasured acids such as ketones, lactate or toxins, and helps classify metabolic acidosis.

The difference between measured serum osmolality and calculated osmolality derived from sodium, glucose and urea. A raised gap indicates the presence of unmeasured osmotically active substances such as ethanol, methanol or ethylene glycol.

A metabolic emergency caused by rapid breakdown of malignant cells, typically after chemotherapy for high-grade lymphoma or leukaemia. It produces hyperkalaemia, hyperphosphataemia, hyperuricaemia and hypocalcaemia, risking acute kidney injury and arrhythmia.

Fever in a patient with a low neutrophil count, usually after cytotoxic chemotherapy, and a medical emergency requiring prompt empirical antibiotics. Signs of infection may be muted because inflammation is impaired, so fever alone may be the only clue.

An abnormally low number of circulating neutrophils, commonly defined as fewer than 1.5 times ten to the power nine per litre, with severe neutropenia below 0.5. It markedly increases susceptibility to bacterial and fungal infection.

Systematic assessment of the extent of a cancer, including tumour size, nodal involvement and distant spread. Stage guides prognosis and treatment choice, and is usually expressed using the TNM system or a numbered grouping.

A scored assessment of consciousness based on eye opening, verbal response and motor response, giving a total from three to fifteen. It is used to grade head injury severity and to detect deterioration in neurological status.

An increase in pressure within the rigid skull, producing headache, vomiting, papilloedema and declining consciousness. It can cause brain herniation and requires urgent measures to reduce volume, such as hyperventilation, osmotic therapy or surgery.

The combination of hypertension with widened pulse pressure, bradycardia and irregular respiration. It signals raised intracranial pressure and impending brainstem herniation, and is a late and ominous finding.

A pregnancy disorder defined by new hypertension with proteinuria or other organ dysfunction after twenty weeks of gestation. It can progress to seizures, liver and kidney injury, and placental insufficiency, and delivery remains the definitive treatment.

The occurrence of generalised seizures in a woman with pre-eclampsia, without another identifiable cause. It is an obstetric emergency managed with magnesium sulphate, blood pressure control and timely delivery.

A severe variant of pre-eclampsia characterised by haemolysis, elevated liver enzymes and low platelets. It causes right upper quadrant pain, malaise and bleeding risk, and may occur with only mildly raised blood pressure.

Excessive bleeding after childbirth, conventionally more than 500 millilitres after vaginal birth or 1000 millilitres after caesarean, or any bleeding causing haemodynamic compromise. Uterine atony is the commonest cause, followed by retained tissue, trauma and clotting disorders.

Raised pressure within a closed fascial compartment that compromises tissue perfusion, causing severe pain out of proportion to injury, pain on passive stretch and later paraesthesia. It is a surgical emergency requiring fasciotomy to prevent muscle and nerve death.

A fracture in which bone communicates with the external environment through a wound in the skin. It carries a high risk of infection and requires early antibiotics, wound cover, tetanus prophylaxis and prompt surgical debridement and stabilisation.

Repeated checking of pulses, capillary refill, colour, warmth, sensation and motor function in a limb after injury or surgery. Deterioration may indicate compartment syndrome, arterial injury or nerve damage and must be acted on urgently.

A technique for emergency tracheal intubation that minimises the interval between loss of protective airway reflexes and securing the airway, reducing aspiration risk. It typically uses a pre-calculated induction dose of an anaesthetic agent with a neuromuscular blocker and avoids bag-mask ventilation.

A rare inherited reaction to volatile anaesthetics and depolarising muscle relaxants, producing rapidly rising temperature, muscle rigidity and hypercapnia. It is treated by stopping the trigger agent and giving dantrolene with supportive cooling and correction of metabolic derangement.

Preoperative evaluation of a patient's anatomy to predict difficulty with mask ventilation or intubation. Features include mouth opening, Mallampati class, thyromental distance, neck mobility and previous airway problems.

A potentially fatal toxidrome caused by excess serotonergic activity, often from combining serotonergic drugs. Features include agitation, tremor, clonus, hyperreflexia, sweating and hyperthermia, and treatment involves stopping the offending agent and supportive care.

A rare idiosyncratic reaction to dopamine-blocking antipsychotics causing rigidity, high fever, altered consciousness and autonomic instability with raised creatine kinase. Management requires stopping the drug, cooling, supportive care and sometimes dantrolene or bromocriptine.

An acute, fluctuating disturbance of attention and awareness, often triggered by infection, drugs, pain or metabolic derangement. It is common in older hospitalised patients and is managed by treating the cause and reducing environmental and sensory stressors.