GCPS Primary Exam cheat sheet

Sensitivity = TP/(TP+FN); specificity = TN/(TN+FP); positive predictive value depends on prevalence, so a sensitive test is best for ruling out disease (SnNout) and a specific test for ruling in (SpPin).

Number needed to treat = 1/absolute risk reduction; number needed to harm = 1/absolute risk increase.

Cardiovascular risk tools (e.g., Framingham, SCORE2, QRISK) estimate 10-year events; statin benefit thresholds are set by 10-year risk, not LDL alone.

Spirometry: FEV1/FVC below 0.70 after bronchodilator supports persistent airflow obstruction; severity is graded by FEV1 percent predicted.

Screening principles (Wilson–Jungner): important disease, accepted treatment, detectable latent stage, suitable test, agreed policy on whom to treat, cost-effective.

Normal adult haemoglobin: men ~13–17 g/dL, women ~12–15 g/dL; anaemia is defined against age- and sex-specific lower limits.

Immunisation schedules are age-banded; live vaccines are contraindicated in significant immunosuppression and in pregnancy.

Antenatal folic acid 400 micrograms daily from preconception reduces neural tube defects; 5 mg is used for prior affected pregnancy or diabetes.

Anion gap = Na − (Cl + HCO3); normal 8–12 mmol/L; raised gap suggests ketoacidosis, lactate, urate, toxins (methanol, ethylene glycol, salicylate) or renal failure.

Winter's formula: expected PaCO2 = 1.5 × HCO3 + 8 ± 2; PaCO2 above the range indicates additional respiratory acidosis.

Serum osmolal gap = measured osmolality − calculated (2Na + glucose + urea); gap >10 suggests an unmeasured osmole.

Corrected calcium (mg/dL) = measured Ca + 0.8 × (4.0 − albumin g/dL).

Acute kidney injury is staged by KDIGO criteria using creatinine rise and urine output; fractional excretion of urea helps in diuretic use.

Troponin rise and fall with ischaemic symptoms or ECG change defines myocardial infarction; type 2 is supply–demand mismatch.

HbA1c reflects ~3 months of glycaemia; it is unreliable in haemoglobinopathies, recent transfusion, pregnancy and iron deficiency.

Hyperkalaemia ECG sequence: peaked T waves, PR prolongation, widened QRS, sine wave; calcium gluconate stabilises the myocardium first.

Pre-analytical error accounts for most laboratory mistakes: haemolysis, delayed processing, wrong tube, underfilled citrate tube (9:1 blood:citrate).

Reference intervals are usually mean ± 2 SD covering ~95% of a healthy population; a result outside the interval is not automatically disease.

Analytical imprecision is expressed as coefficient of variation; sigma metrics relate allowable total error to assay CV and bias.

Tumour markers (CEA, CA-125, AFP, PSA) are for monitoring and follow-up, not stand-alone diagnosis; AFP also rises in hepatocellular carcinoma.

Blood cultures: two to three sets from separate sites before antibiotics; each set includes one aerobic and one anaerobic bottle.

Gram stain classification depends on peptidoglycan thickness; culture requires correct media and atmosphere (e.g., capnophilic for Campylobacter).

Coagulation: INR standardises prothrombin time using the ISI of the thromboplastin; APTT monitors unfractionated heparin.

Quality control uses Westgard rules; a 1-3s rule signals random error, while 2-2s and R-4s suggest systematic error.

TNM staging: T = primary tumour extent, N = regional nodes, M = distant metastasis; prefix c = clinical, p = pathological, y = post-neoadjuvant.

Radiotherapy dose is measured in gray (1 Gy = 1 J/kg); fractionation exploits the 4 R's: repair, repopulation, redistribution, reoxygenation.

Therapeutic ratio maximised by fraction size and total dose; conventional fractionation is ~1.8–2 Gy per fraction, 5 days per week.

Linear energy transfer and relative biological effectiveness: high-LET radiation (protons, neutrons) has greater RBE and a sharper Bragg peak.

Chemotherapy cell kill follows first-order (log-kill) kinetics; combination regimens use non-overlapping toxicity and different mechanisms.

Common paraneoplastic syndromes: SIADH (small cell lung), hypercalcaemia (squamous lung, myeloma), Cushing (small cell, carcinoid).

Neutropenic sepsis: fever ≥38.0 °C with neutrophils <0.5 × 10⁹/L requires immediate empiric broad-spectrum antibiotics.

Tumour lysis syndrome: hyperkalaemia, hyperphosphataemia, hyperuricaemia, hypocalcaemia; prevent with hydration and allopurinol or rasburicase.

APGAR scores at 1 and 5 minutes: Appearance, Pulse, Grimace, Activity, Respiration; each 0–2, total 0–10.

Normal neonatal respiratory rate 30–60/min; grunting, recession and nasal flaring indicate respiratory distress.

Paediatric weight estimate: 0–12 months ≈ (age in months + 9)/2 kg; 1–5 years ≈ 2 × (age in years + 4).

Neonatal jaundice appearing within 24 hours is always pathological; unconjugated hyperbilirubinaemia risks kernicterus.

Developmental milestones: social smile 6 weeks, head control 3 months, sitting 6–8 months, walking 12–18 months, two-word phrases 18–24 months.

Fluid maintenance by Holliday–Segar: 100 mL/kg for first 10 kg, 50 for next 10, 20 for each kg thereafter.

Congenital heart disease: cyanotic lesions are the 5 T's - truncus arteriosus, transposition, tricuspid atresia, tetralogy of Fallot, total anomalous pulmonary venous return.

Kawasaki disease: fever ≥5 days plus 4 of 5 features; IVIG and aspirin reduce coronary artery aneurysm risk.

Depression requires ≥2 weeks of low mood or anhedonia plus ≥4 of: sleep, interest, guilt, energy, concentration, appetite, psychomotor change, suicidal ideation.

Delirium is acute, fluctuating, with inattention; dementia is chronic and progressive; depression can mimic both (pseudodementia).

First-rank (Schneiderian) symptoms include thought insertion, withdrawal, broadcasting, passivity phenomena and third-person auditory hallucinations.

Serotonin syndrome: clonus, hyperreflexia, agitation, fever; neuroleptic malignant syndrome: rigidity, hyperthermia, autonomic instability, raised CK.

Lithium has a narrow therapeutic index (0.6–1.0 mmol/L); toxicity presents with tremor, ataxia, vomiting and renal impairment.

Alcohol withdrawal: tremor, sweating, tachycardia at 6–12 h; seizures at 12–48 h; delirium tremens at 48–96 h; treat with benzodiazepines and thiamine.

Mental capacity assessment requires understanding, retention, communication and weighing of information, not the decision's apparent wisdom.

Antipsychotic prolactin elevation is highest with risperidone and haloperidol; clozapine requires regular full blood count monitoring for neutropenia.

Incidence counts new cases per population at risk per time; prevalence counts all existing cases at a point or period.

Relative risk = incidence in exposed / incidence in unexposed; odds ratio approximates RR when disease is rare.

Attributable risk (risk difference) = incidence in exposed − incidence in unexposed; population attributable fraction = (I_total − I_unexposed)/I_total.

Herd immunity threshold = 1 − 1/R0; measles R0 ~12–18, so very high coverage is needed.

Screening test performance: sensitivity, specificity, positive and negative predictive values; PPV rises as prevalence rises.

Study designs: cohort gives incidence and RR; case–control gives OR; randomised controlled trial reduces confounding by randomisation.

Bias types: selection, information, recall, confounding, lead-time and length-time bias in screening.

Outbreak investigation steps: verify diagnosis, define case, describe by person/place/time, generate hypothesis, control, communicate.

Radiation dose: absorbed dose in gray (Gy), equivalent dose in sievert (Sv) with tissue weighting, effective dose sums weighted organ doses.

ALARA principle: dose as low as reasonably achievable; justify every exposure and use the lowest adequate modality.

CT uses ionising X-rays with higher dose than plain film; MRI uses no ionising radiation but is contraindicated with some implants and pacemakers.

Ultrasound is first-line for suspected gallstones, obstetric assessment and many soft-tissue questions; it is operator dependent.

Contrast: iodinated contrast is nephrotoxic and can cause anaphylactoid reactions; gadolinium is avoided in severe renal impairment (NSF risk).

Chest X-ray: silhouette sign localises opacity; air bronchograms suggest alveolar disease; pneumothorax shows a visible pleural line with absent distal markings.

Acute stroke: non-contrast CT excludes haemorrhage; early ischaemic signs include loss of grey–white differentiation and the hyperdense MCA sign.

Bone: fracture lines, periosteal reaction and growth-plate appearances differ by age; a Salter–Harris classification describes paediatric physeal injuries.

Pre-oxygenation with 100% oxygen for 3 minutes creates an oxygen reserve; rapid sequence induction uses a predetermined induction agent plus neuromuscular blocker.

MAC (minimum alveolar concentration) is the alveolar concentration preventing movement to a standard stimulus in 50% of patients; it is additive across agents.

Depolarising blocker succinylcholine causes fasciculations and can trigger hyperkalaemia and malignant hyperthermia; non-depolarisers are competitive antagonists.

Malignant hyperthermia: rising end-tidal CO2, masseter spasm, hyperthermia, rigidity; treat with dantrolene and stop triggering agents.

Local anaesthetic systemic toxicity: perioral tingling, tinnitus, seizures, arrhythmias; intralipid is the specific rescue therapy.

Spinal anaesthesia blocks sympathetic fibres first (T1–L2), causing hypotension; treat with fluids and vasopressors.

Difficult airway algorithm: optimise, call for help, supraglottic rescue, then surgical front-of-neck access as the final step.

Postoperative nausea and vomiting risk factors (Apfel): female sex, non-smoker, history of PONV, postoperative opioids.

Tooth numbering: FDI system uses two digits, quadrant 1–4 then tooth 1–8; permanent upper right third molar is 18.

Dental caries is a biofilm-driven demineralisation; fluoride promotes remineralisation and reduces enamel solubility.

Pulpitis: reversible pain to thermal stimulus only; irreversible pulpitis gives spontaneous or lingering pain, often requiring endodontics.

Periodontal disease severity is classified by clinical attachment loss and probing depth; smoking and diabetes are major risk factors.

Local anaesthetic in dentistry: articaine and lidocaine with adrenaline; maximum lidocaine dose ~4.4 mg/kg (7 mg/kg with adrenaline).

Odontogenic infection spread: submandibular and sublingual spaces communicate via the mylohyoid; Ludwig's angina is a bilateral floor-of-mouth cellulitis requiring urgent airway and surgical drainage.

Dry socket (alveolar osteitis) presents 2–4 days after extraction with severe pain and empty socket; treat with irrigation and dressing.

Oral potentially malignant disorders include leukoplakia, erythroplakia and submucous fibrosis; biopsy is required for definitive diagnosis.

ABCDE approach: Airway, Breathing, Circulation, Disability, Exposure; reassess after every intervention.

Shock types: hypovolaemic, cardiogenic, distributive (septic, anaphylactic, neurogenic), obstructive (tamponade, tension pneumothorax, massive PE).

Anaphylaxis: intramuscular adrenaline 0.5 mg (1 mg/mL) into the anterolateral thigh, repeated every 5 minutes; adjuncts are antihistamine and steroid.

Sepsis-3: suspected infection plus SOFA increase ≥2; qSOFA uses respiratory rate ≥22, altered mentation, systolic BP ≤100.

Tension pneumothorax is a clinical diagnosis; immediate needle decompression precedes imaging.

Glasgow Coma Scale: eye 1–4, verbal 1–5, motor 1–6; total 3–15; score ≤8 indicates need for airway protection.

Burns: Parkland formula 4 mL × body weight (kg) × %TBSA for 24 h, half in the first 8 h; use the Rule of Nines for extent.

Poisoning: activated charcoal within 1 h for appropriate ingestions; naloxone for opioids, N-acetylcysteine for paracetamol, and check timed paracetamol level against the nomogram.

Monro–Kellie doctrine: the skull is a rigid container; brain, blood and CSF volumes are constant, so any increase raises intracranial pressure.

Cerebral perfusion pressure = mean arterial pressure − intracranial pressure; normal ICP is 5–15 mmHg.

Raised ICP: headache, vomiting, papilloedema, reduced consciousness, Cushing's triad (hypertension, bradycardia, irregular respiration).

Glasgow Coma Scale scoring and pupillary signs localise lesions; a fixed dilated pupil suggests ipsilateral uncal herniation.

Subarachnoid haemorrhage: sudden thunderclap headache; CT within 6 h is highly sensitive; xanthochromia in CSF after 12 h.

Extradural haematoma is lens-shaped and does not cross sutures; subdural is crescentic and crosses sutures.

Spinal cord injury: ASIA scale grades A–E; high-dose steroids are not routine; immobilise and image.

Hydrocephalus: communicating versus non-communicating; treatment options include ventriculoperitoneal shunt and endoscopic third ventriculostomy.

Estimated date of delivery: Naegele's rule - first day of last menstrual period + 280 days (or + 9 months + 7 days).

Stages of labour: first stage to full dilatation, second stage to delivery, third stage to placental expulsion (normally <30 min).

Cardiotocography: baseline rate 110–160/min; late decelerations suggest uteroplacental insufficiency, variable decelerations suggest cord compression.

Postpartum haemorrhage: >500 mL after vaginal or >1000 mL after caesarean delivery; the 4 T's are tone, trauma, tissue, thrombin.

Pre-eclampsia: hypertension after 20 weeks plus proteinuria or end-organ dysfunction; magnesium sulfate prevents and treats eclampsia.

Ectopic pregnancy: risk factors include previous ectopic, tubal surgery, PID and IUCD; transvaginal ultrasound plus serial beta-hCG.

Ovarian cancer: CA-125 is raised but nonspecific; risk of malignancy index combines CA-125, menopausal status and ultrasound features.

Contraception: combined oral contraceptive is contraindicated in migraine with aura, smoker over 35, and history of VTE.

Visual acuity is recorded as Snellen fraction; 6/6 is normal; pinhole improvement suggests refractive error.

Pupil light reflex: afferent defect (relative afferent pupillary defect) indicates optic nerve or severe retinal disease.

Acute angle-closure glaucoma: painful red eye, fixed mid-dilated pupil, hazy cornea, raised intraocular pressure; treat with topical and systemic pressure-lowering agents plus laser iridotomy.

Central retinal artery occlusion causes sudden painless monocular loss with a cherry-red spot; giant cell arteritis can cause anterior ischaemic optic neuropathy.

Diabetic retinopathy: non-proliferative with microaneurysms and haemorrhages; proliferative with neovascularisation requiring laser or anti-VEGF.

Retinal detachment: flashes, floaters, field defect; macula-on is an emergency for surgery.

Conjunctivitis versus keratitis: corneal involvement causes pain, photophobia and reduced vision; fluorescein staining shows epithelial defect.

Ocular trauma: chemical injury requires immediate copious irrigation; intraocular foreign body needs imaging and specialist referral.

Fracture description: site, pattern (transverse, oblique, spiral, comminuted), displacement, angulation, rotation, shortening, intra-articular involvement.

Bone healing: haematoma, inflammation, soft callus, hard callus, remodelling; smoking and NSAIDs impair healing.

Compartment syndrome: pain out of proportion, pain on passive stretch, paraesthesia; pulses may remain; fasciotomy is urgent.

Open fracture management: antibiotics within 1 hour, tetanus prophylaxis, debridement and stabilisation; Gustilo–Anderson classification guides treatment.

Hip fracture: intracapsular (femoral neck) risks avascular necrosis; extracapsular (intertrochanteric) is treated with fixation; surgery within 48 h improves outcomes.

Osteoarthritis: joint space narrowing, osteophytes, subchondral sclerosis and cysts; weight loss and exercise are core treatments.

Osteomyelitis: Staphylococcus aureus is the commonest cause; MRI is sensitive; prolonged antibiotics plus surgical debridement.

Peripheral nerve injury classification (Seddon): neurapraxia, axonotmesis, neurotmesis; recovery depends on the level and type of injury.

Epistaxis: most arise from Little's area (Kiesselbach's plexus); posterior bleeds are more severe and may require packing or arterial ligation.

Otitis media with effusion: glue ear; tympanometry shows a flat (type B) trace; grommets for persistent hearing loss.

Cholesteatoma: keratinising squamous epithelium in the middle ear; causes foul discharge and bone erosion; treatment is surgical.

Vertigo: benign paroxysmal positional vertigo is diagnosed by the Dix–Hallpike test and treated with the Epley manoeuvre.

Meniere's disease: episodic vertigo, fluctuating hearing loss, tinnitus and aural fullness; low-salt diet and betahistine are used.

Sudden sensorineural hearing loss is an emergency; high-dose corticosteroids improve recovery.

Tonsillitis: recurrent cases may warrant tonsillectomy; peritonsillar abscess (quinsy) causes trismus and uvular deviation, requiring drainage.

Head and neck cancer: hoarseness >3 weeks, neck lump, otalgia and dysphagia warrant urgent referral and endoscopy with biopsy.

Wound healing phases: haemostasis, inflammation, proliferation (fibroblasts, angiogenesis), remodelling; collagen type III is replaced by type I.

Surgical site infection prevention: aseptic technique, appropriate antibiotic prophylaxis within 60 minutes of incision, normothermia and glycaemic control.

Abdominal pain: peritonitis suggests a surgical cause; rigidity and rebound tenderness are signs of peritoneal irritation.

Appendicitis: migration of pain to the right iliac fossa, anorexia, low-grade fever; Alvarado score aids assessment; ultrasound or CT confirms.

Bowel obstruction: colicky pain, vomiting, distension, absolute constipation; look for hernia, adhesions and malignancy.

Hernia: inguinal (indirect passes through the deep ring; direct through Hesselbach's triangle); strangulation is a surgical emergency.

Thyroid surgery risks: recurrent laryngeal nerve injury (hoarseness), external branch of superior laryngeal nerve, hypocalcaemia from parathyroid injury.

Postoperative complications: atelectasis and VTE early, wound infection around day 5, anastomotic leak around day 5–7, incisional hernia late.