WACP Primary cheat sheet

Incidence = new cases / population at risk per unit time; prevalence = all existing cases / total population (prevalence ≈ incidence × duration for stable disease).

Attack rate = (new cases among exposed / total exposed) × 100; used in outbreak investigations of point-source exposure.

Sensitivity = TP/(TP+FN); specificity = TN/(TN+FP); PPV = TP/(TP+FP) and is prevalence-dependent; NPV = TN/(TN+FN).

Relative risk (cohort) = incidence in exposed / incidence in unexposed; odds ratio (case-control) approximates RR when disease is rare (<10%).

Attributable risk (risk difference) = incidence exposed − incidence unexposed; population attributable fraction = (Ipop − Iunexposed)/Ipop.

Herd immunity threshold = 1 − 1/R0; for measles (R0 12–18) this requires ~92–95% two-dose coverage.

Levels of prevention: primary (pre-exposure), secondary (early detection/screening), tertiary (disability limitation/rehabilitation); screening requires a detectable latent phase and an accepted treatment.

Lead-time bias inflates survival without changing mortality; length bias over-represents slow-growing disease in screening trials; healthy worker effect lowers observed occupational mortality.

Notifiable disease reporting, cold-chain vaccine handling (+2 to +8 °C), and KEPI schedule (BCG and OPV at birth; pentavalent at 6, 10, 14 weeks; measles at 9 and 15 months) are core programmatic facts.

WHO analgesic ladder: step 1 non-opioid (paracetamol/NSAID), step 2 weak opioid (codeine/tramadol), step 3 strong opioid (morphine); adjuvants at any step.

Paracetamol dose 10–15 mg/kg/dose every 4–6 h (max 75 mg/kg/day or 4 g/day adult); overdose antidote N-acetylcysteine, most effective within 8 h.

Ibuprofen 5–10 mg/kg/dose every 6–8 h (max 40 mg/kg/day); avoid in dehydration, renal impairment, and third-trimester pregnancy.

Oral rehydration solution: reduced-osmolarity (245 mOsm/L, Na 75 mmol/L); give 50–100 mL/kg over 3–4 h for some dehydration plus replacement of ongoing losses.

Zinc 20 mg/day (10 mg if <6 months) for 10–14 days shortens diarrhoea duration and reduces recurrence.

Integrated Management of Childhood Illness (IMCI) danger signs: inability to drink/breastfeed, persistent vomiting, convulsions, lethargy/unconsciousness, stridor at rest, severe malnutrition.

Contraceptive effectiveness (typical use): implant/IUD >99%, injectable ~94%, COC ~91%, condom ~87%; emergency contraception (levonorgestrel) within 72 h, copper IUD within 5 days.

Spirometry: FEV1/FVC <0.70 post-bronchodilator confirms airflow obstruction; asthma shows ≥12% and ≥200 mL reversibility.

Screening thresholds: BP ≥140/90 mmHg (or ≥130/80 in diabetes/CKD), fasting glucose ≥7.0 mmol/L or HbA1c ≥6.5% for diabetes.

Acid–base: anion gap = Na − (Cl + HCO3), normal 8–12 mmol/L; corrected Na = measured Na + 0.3 × (glucose − 5.5) for hyperglycaemia.

Winter's formula: expected PaCO2 = 1.5 × HCO3 + 8 ± 2; delta ratio = Δ anion gap / Δ HCO3 (1–2 = pure high-AG acidosis).

Acute kidney injury KDIGO: creatinine rise ≥26.5 µmol/L in 48 h or ≥1.5× baseline in 7 days, or urine output <0.5 mL/kg/h for 6 h.

Hyponatraemia correction limit: ≤8–10 mmol/L in 24 h to avoid osmotic demyelination; hyperkalaemia: calcium gluconate first if ECG changes, then insulin–dextrose and salbutamol.

Acute coronary syndrome: troponin rise/fall with ischaemic symptoms; STEMI requires urgent reperfusion (PCI within 120 min); dual antiplatelet plus anticoagulation.

Heart failure: reduced EF ≤40%; treat with ACE inhibitor/ARB or ARNI, beta-blocker, MRA, and SGLT2 inhibitor; loop diuretics for congestion.

Community-acquired pneumonia severity: CURB-65 (confusion, urea >7 mmol/L, RR ≥30, BP <90/60, age ≥65); score ≥2 suggests admission.

Stroke: thrombolysis within 4.5 h of onset; thrombectomy up to 24 h in selected large-vessel occlusion; aspirin within 48 h after haemorrhage excluded.

Sepsis-3: suspected infection plus SOFA increase ≥2; septic shock = persistent hypotension requiring vasopressors with lactate >2 mmol/L despite fluid resuscitation.

Reference intervals typically cover the central 95% of a healthy population (2.5th–97.5th percentile).

Sensitivity = TP/(TP+FN); specificity = TN/(TN+FP); likelihood ratio positive = sensitivity/(1 − specificity); LR negative = (1 − sensitivity)/specificity.

Pre-analytical errors account for most laboratory mistakes: wrong tube, haemolysis, delayed processing, incorrect tourniquet time.

Complete blood count: Hb (g/L), MCV (fL), MCH, WBC with differential, platelets; MCV <80 fL microcytic (iron deficiency, thalassaemia), >100 fL macrocytic (B12/folate, alcohol).

Iron studies: low ferritin (<30 µg/L) is most specific for iron deficiency; ferritin is an acute-phase reactant and may be normal in inflammation.

Liver enzymes: ALT more liver-specific than AST; AST:ALT >2 suggests alcohol; ALP rises in cholestasis and bone disease; bilirubin fractionation distinguishes pre-hepatic, hepatic, and post-hepatic jaundice.

Renal function: eGFR from creatinine (CKD-EPI); urea:creatinine ratio >20:1 suggests pre-renal azotaemia; urine Na <20 mmol/L supports pre-renal state.

Coagulation: PT/INR (extrinsic), APTT (intrinsic), thrombin time/fibrinogen; mixing study corrects factor deficiency but not inhibitor.

Blood culture: obtain before antibiotics, two sets from separate sites, 20–30 mL total; incubation 5 days standard.

Neonatal resuscitation: dry, stimulate, position; if apnoeic or HR <100 give positive-pressure ventilation; chest compressions if HR <60 after effective ventilation; 3:1 compression:ventilation ratio.

APGAR at 1 and 5 min: Appearance, Pulse (<100 = 1, >100 = 2), Grimace, Activity, Respiration; score 0–10, not used to guide resuscitation.

Weight estimation: 0–12 months weight (kg) = (age in months + 9)/2; 1–6 years = 2 × (age + 4); 7–12 years = 7 × age − 5 / 2.

Paediatric maintenance fluids (Holliday–Segar): 100 mL/kg/day for first 10 kg, 50 for next 10, 20 for each kg thereafter.

Growth: birth weight doubles by 5 months, triples by 12 months; length increases ~25 cm in first year; head circumference +12 cm in first year.

Developmental milestones: social smile 6 weeks, head control 3 months, sits unsupported 6–8 months, walks 12–15 months, two-word phrases 18–24 months.

Jaundice: pathological if <24 h of age, bilirubin rising >85 µmol/L/day, conjugated fraction >20% or persists >14 days; treat with phototherapy per nomogram.

Kwashiorhor (oedematous malnutrition) vs marasmus (non-oedematous wasting); refeeding syndrome risk - monitor phosphate, potassium, magnesium.

Paediatric dosing: paracetamol 10–15 mg/kg/dose q4–6h; amoxicillin 25–45 mg/kg/day divided; check weight-based dosing and maximum adult dose.

Depression: ≥5 of 9 DSM-5 criteria for ≥2 weeks including depressed mood or anhedonia; severity guides treatment (psychotherapy for mild, antidepressant plus therapy for moderate–severe).

Suicide risk assessment: ideation, plan, intent, means, previous attempts, substance use, protective factors; ask directly - asking does not increase risk.

Serotonin syndrome: clonus, hyperreflexia, agitation, hyperthermia after serotonergic agents; stop offending drugs, supportive care, cyproheptadine in severe cases.

Neuroleptic malignant syndrome: rigidity, hyperthermia, autonomic instability, raised CK after antipsychotics; stop drug, dantrolene or bromocriptine, supportive care.

First-rank (Schneiderian) symptoms of schizophrenia: auditory hallucinations (third-person, running commentary), thought insertion/withdrawal/broadcast, passivity phenomena.

Alcohol withdrawal: tremor, anxiety, seizures at 6–48 h, delirium tremens at 48–96 h; treat with benzodiazepines (chlordiazepoxide) and thiamine before glucose.

Bipolar disorder: mania = elevated/irritable mood plus increased energy for ≥1 week with ≥3 of grandiosity, decreased sleep, pressured speech, flight of ideas, distractibility, risky behaviour.

Antipsychotic monitoring: weight, BMI, waist, BP, fasting glucose/HbA1c, lipids at baseline, 6 weeks, 3 months, then annually; ECG if QT risk.

Postpartum psychosis is a psychiatric emergency: onset within 2 weeks of delivery, hallucinations/delusions, risk of infanticide; requires urgent admission and antipsychotic treatment.