GCPS Primary Exam flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Sensitivity

Proportion of people with disease who test positive (TP/(TP+FN)). A highly sensitive test is useful for ruling out disease when negative.

Specificity

Proportion of people without disease who test negative (TN/(TN+FP)). A highly specific test is useful for ruling in disease when positive.

Number needed to treat

Inverse of absolute risk reduction: NNT = 1/ARR. It states how many patients must be treated for one additional favourable outcome.

Anion gap

Calculated as sodium minus (chloride plus bicarbonate). A raised gap indicates accumulation of unmeasured anions such as ketones, lactate or toxins.

Winter's formula

Expected PaCO2 in metabolic acidosis = 1.5 × bicarbonate + 8 ± 2. A measured PaCO2 outside this range indicates a second respiratory disorder.

Holliday–Segar maintenance

Paediatric hourly fluid maintenance: 100 mL/kg for the first 10 kg, 50 mL/kg for the next 10 kg, and 20 mL/kg for each kilogram thereafter.

APGAR score

Assessed at 1 and 5 minutes: appearance, pulse, grimace, activity and respiration, each scored 0–2. Total 0–10; 7–10 is generally reassuring.

Herd immunity threshold

Proportion of a population that must be immune to interrupt transmission, calculated as 1 − 1/R0. Higher R0 requires higher vaccine coverage.

Relative risk

Incidence of disease in the exposed group divided by incidence in the unexposed group. Used in cohort studies and randomised trials.

Odds ratio

Ratio of odds of exposure in cases to odds of exposure in controls. Approximates relative risk when the disease is rare.

Lead-time bias

Apparent survival gain from screening because diagnosis is made earlier, without any real extension of life. Screening trials need mortality endpoints.

Gray (Gy)

Unit of absorbed radiation dose equal to one joule per kilogram. Radiotherapy total doses are prescribed in gray and divided into fractions.

Therapeutic ratio

Balance between tumour cell kill and normal tissue damage. Fractionation and conformal techniques increase tumour dose while sparing normal tissue.

Tumour lysis syndrome

Metabolic emergency after rapid tumour breakdown: hyperkalaemia, hyperphosphataemia, hyperuricaemia and hypocalcaemia. Prevented with hydration and allopurinol.

Neutropenic sepsis

Fever with neutrophil count below 0.5 × 10⁹/L. Requires immediate empiric broad-spectrum antibiotics; do not wait for culture results.

Delirium versus dementia

Delirium is acute, fluctuating and marked by inattention; dementia is chronic and progressive. Delirium is a medical emergency needing a cause.

Serotonin syndrome

Caused by serotonergic excess: clonus, hyperreflexia, agitation and fever. Contrast with neuroleptic malignant syndrome, which shows rigidity and raised creatine kinase.

Schneiderian first-rank symptoms

Psychotic features including thought insertion, withdrawal or broadcasting, passivity phenomena and third-person auditory hallucinations, classically associated with schizophrenia.

ALARA principle

Radiation protection principle: dose as low as reasonably achievable. Every exposure must be justified and optimised for the clinical question.

Silhouette sign

Loss of the normal border between adjacent structures of similar density on chest radiography, used to localise an opacity to a specific lobe.

Minimum alveolar concentration

Alveolar concentration of volatile anaesthetic preventing movement to a standard stimulus in 50% of patients. Values are additive between agents.

Malignant hyperthermia

Pharmacogenetic reaction to volatile agents or succinylcholine: rising end-tidal CO2, rigidity and hyperthermia. Stop triggers and give dantrolene.

Local anaesthetic systemic toxicity

Neurological symptoms (tinnitus, perioral tingling, seizures) followed by arrhythmias and cardiac arrest. Intravenous lipid emulsion is the specific rescue.

Ludwig's angina

Rapidly spreading bilateral cellulitis of the submandibular and sublingual spaces. Threatens the airway and requires urgent antibiotics and surgical drainage.

Lens-shaped haematoma

Extradural haematoma: biconvex collection that does not cross sutures, typically from middle meningeal artery injury. Subdural is crescentic and crosses sutures.

Cushing's triad

Raised intracranial pressure signs: hypertension, bradycardia and irregular respiration. Indicates impending herniation and requires urgent decompression.

Cerebral perfusion pressure

Mean arterial pressure minus intracranial pressure. Normal ICP is 5–15 mmHg; falling perfusion pressure threatens cerebral ischaemia.

Naegele's rule

Estimated delivery date from the first day of the last menstrual period plus 280 days, or plus 9 months and 7 days.

Postpartum haemorrhage

Blood loss over 500 mL after vaginal delivery or 1000 mL after caesarean. Causes are the four T's: tone, trauma, tissue and thrombin.

Relative afferent pupillary defect

Asymmetric pupil constriction during the swinging flashlight test, indicating optic nerve or severe retinal disease on that side.

Compartment syndrome

Increased pressure within a closed fascial compartment causing pain out of proportion, pain on passive stretch and paraesthesia. Requires urgent fasciotomy.

Dix–Hallpike test

Positioning manoeuvre that provokes nystagmus and vertigo in benign paroxysmal positional vertigo; a positive test is treated with the Epley manoeuvre.