Egyptian Board Internal Medicine common mistakes
Egyptian Board Internal Medicine · Understand the traps and how to avoid them.
When a stem gives an arterial blood gas with a normal or near-normal PaCO2 in a patient who is clearly tachypneic and hypoxemic, the candidate labels the picture 'normal ventilation' and moves straight to oxygen therapy, never calculating the alveolar-arterial (A-a) gradient or the expected compensatory response.
Candidates memorize the primary acid-base disorders (metabolic acidosis, respiratory alkalosis, etc.) as isolated patterns and do not routinely apply the compensation formulas or the A-a gradient. In Egypt the ABG is a very common stem format, and the candidate reads the pH/PaCO2 pair as a diagnosis rather than as a test of the adequacy of compensation, so a raised A-a gradient in a young patient with a normal chest radiograph (suggesting pulmonary embolism or an intracardiac shunt) is missed.
What to do instead
Build a fixed ABG algorithm and rehearse it on every gas: (1) identify the primary disorder from pH and PaCO2/HCO3; (2) check whether compensation is appropriate using Winter's formula for metabolic acidosis (expected PaCO2 = 1.5 x HCO3 + 8 +/- 2) and the expected change in HCO3 for acute versus chronic respiratory disorders; (3) if hypoxemic, calculate the A-a gradient (PAO2 = FiO2 x (760 - 47) - PaCO2/0.8) and interpret it against age. Write the three numbers down before choosing an answer.
In a breathless patient with a normal chest radiograph, the candidate stops at 'no consolidation, no effusion' and does not weigh pretest probability for pulmonary embolism, does not request D-dimer or CT pulmonary angiography, and does not consider the possibility that the presentation is a mimic (heart failure, anemia, metabolic acidosis, pulmonary hypertension).
The candidate treats the chest radiograph as the definitive respiratory investigation rather than one test among several, and under-weights the clinical probability (Wells score, PERC, gestalt). Examiners deliberately construct stems where the radiograph is normal precisely to test whether the candidate escalates to the correct next test.
What to do instead
For every dyspnea stem, explicitly state the pretest probability category before selecting an investigation, then choose the test that changes management at that probability (D-dimer to rule out in low/intermediate probability, CTPA to rule in). Practice writing one sentence of justification for each imaging choice, because the exam rewards the correct sequence, not just the correct final diagnosis.
Faced with a patient who has ascites, the candidate orders a diagnostic tap but interprets the serum-ascites albumin gradient (SAAG) as an 'exudate/transudate' label and does not use it to separate portal hypertension from other causes; the ascitic fluid neutrophil count and culture are not checked before deciding on antibiotics.
Candidates carry over the pleural fluid transudate/exudate framework and misapply it to ascites. The SAAG (serum albumin minus ascitic albumin, with a cutoff around 1.1 g/dL) is the correct discriminator, and spontaneous bacterial peritonitis is a diagnosis made on a polymorphonuclear cell count of 250/mm3 or more, often with a negative culture. The candidate treats ascites as a single disease rather than as a sign requiring a cause and a complication screen.
What to do instead
For every ascites stem, calculate the SAAG and state whether it indicates portal hypertension (>=1.1 g/dL: cirrhosis, cardiac failure, Budd-Chiari) or not (<1.1 g/dL: peritoneal carcinomatosis, tuberculosis, pancreatic ascites). Always send cell count with differential and inoculate blood culture bottles at the bedside. In a cirrhotic with ascites and fever or encephalopathy, start empirical third-generation cephalosporin after the tap, without waiting for culture.
When a stem reports a sodium of 118 mmol/L, the candidate immediately selects hypertonic saline and a rapid correction rate, or conversely corrects a chronic hyponatremia at the same speed as an acute one, without first classifying the patient by volume status and urine osmolality.
The candidate conflates 'dangerous number' with 'emergency' and does not distinguish symptomatic from asymptomatic hyponatremia, or acute from chronic. The rate of correction (typically no more than 8-10 mmol/L in 24 hours in chronic cases) exists to prevent osmotic demyelination, and the choice of fluid depends on volume status and urine electrolytes. Egyptian exam stems frequently include a urine sodium and urine osmolality that are meant to drive the answer.
What to do instead
Use a fixed sequence: confirm true hypotonic hyponatremia with a measured serum osmolality; assess volume status; check urine osmolality and urine sodium to classify (hypovolemic, euvolemic such as SIADH, hypervolemic). Reserve hypertonic saline for severe symptoms (seizure, coma, vomiting) with a small bolus and a defined ceiling on the 24-hour rise. For SIADH, fluid restriction is first-line; for hypovolemia, isotonic saline. State the target correction rate in the answer.
In a diabetic patient with a glucose of 480 mg/dL and ketonuria, the candidate writes 'DKA' and orders insulin but does not check the potassium before starting the infusion, does not give fluids first, and does not look for the precipitant (infection, myocardial infarction, non-adherence, new-onset diabetes).
Candidates memorize the triad (hyperglycemia, ketosis, acidosis) but not the management sequence. Insulin drives potassium into cells and can precipitate fatal hypokalemia if the potassium is already low; total-body potassium is depleted in DKA even when the serum value looks normal or high. The precipitant search is the part that determines outcome and is frequently the tested point.
What to do instead
For every DKA/HHS stem, state the potassium and act on it: if K+ is below about 3.3 mmol/L, hold insulin and give potassium first; if 3.3-5.2, give insulin and replace potassium; if above 5.2, give insulin and recheck. Write the fluid plan (isotonic saline), the insulin protocol (fixed-rate infusion, not sliding scale), the potassium plan, and the precipitant workup (ECG, cultures, urinalysis, pregnancy test where relevant) in that order.
Given a microcytic anemia, the candidate jumps to iron deficiency without checking the ferritin, transferrin saturation, and the red cell distribution width, and does not consider thalassemia trait, anemia of chronic disease, or sideroblastic anemia, nor does the candidate ask about the source of blood loss in an adult man or postmenopausal woman.
Iron deficiency is the most common cause and the candidate pattern-matches to it. But ferritin is an acute-phase reactant and can be falsely normal in inflammation, thalassemia trait shows a normal or high ferritin with a low MCV and a high red cell count, and iron deficiency in an adult man or postmenopausal woman is a gastrointestinal malignancy until proven otherwise. The exam tests the discrimination, not the label.
What to do instead
For every microcytic anemia, state ferritin, transferrin saturation, and RDW, and use them to separate the causes: low ferritin with high RDW suggests iron deficiency; normal ferritin with low MCV and high RBC count suggests thalassemia trait (confirm with hemoglobin electrophoresis); low saturation with normal or high ferritin suggests anemia of chronic disease. Always add the source search: fecal occult blood, endoscopy and colonoscopy in the appropriate age and sex, and menstrual history in women.
In a patient with a swollen joint, the candidate diagnoses gout from the serum uric acid alone, or treats a possible septic joint with antibiotics without aspirating first, or starts allopurinol during an acute attack without addressing the acute inflammation.
The candidate treats the serum uric acid as diagnostic, but it can be normal during an acute attack and raised in asymptomatic people. The single most important test in a hot joint is synovial fluid analysis (cell count, Gram stain, culture, and crystals under polarized light), because septic arthritis and crystal arthritis can coexist. The exam often presents a joint that could be either.
What to do instead
For every acute monoarthritis stem, state that arthrocentesis is the first investigation and interpret the synovial fluid: cell count above about 50,000/mm3 with a neutrophil predominance and positive Gram stain favors septic arthritis; needle-shaped negatively birefringent crystals indicate gout; rhomboid positively birefringent crystals indicate pseudogout. Treat septic arthritis with empirical intravenous antibiotics after aspiration and do not delay for imaging. In gout, treat the acute attack with NSAIDs, colchicine, or corticosteroids, and start urate-lowering therapy with prophylaxis, not as an emergency.
Presented with a patient who has fever, headache, and neck stiffness, the candidate orders a CT scan before antibiotics and lumbar puncture, and does not give dexamethasone with the first antibiotic dose; or the candidate performs a lumbar puncture in a patient with focal signs or papilledema without first imaging.
Candidates sequence the investigations in the order they would be reported (imaging, then LP, then culture) rather than in the order that saves life. In bacterial meningitis, antibiotics should not be delayed for imaging or LP when the diagnosis is suspected; dexamethasone before or with the first antibiotic dose reduces hearing loss and neurologic sequelae in pneumococcal disease. The contraindications to immediate LP (focal deficit, seizures, papilledema, immunocompromise, coagulopathy) are the tested discriminator.
What to do instead
Write the order explicitly: blood cultures, then empirical antibiotics (third-generation cephalosporin plus vancomycin where pneumococcal resistance is a concern, with ampicillin added in the elderly or immunocompromised for Listeria), then dexamethasone, then CT only if there is a contraindication to immediate LP, then LP when safe. State the LP contraindications before the LP in the answer.
In a patient with an acute ischemic stroke within the thrombolysis window, the candidate forgets to check the blood glucose and blood pressure before deciding on thrombolysis, or fails to calculate the door-to-needle time and the contraindications (recent surgery, anticoagulation, platelet count, INR).
The candidate focuses on the time window alone and treats it as the only criterion. Hypoglycemia is a stroke mimic and must be excluded before any thrombolysis decision; blood pressure above 185/110 mmHg must be lowered before thrombolysis; and the absolute contraindications (recent intracranial surgery, active bleeding, anticoagulation with an elevated INR, platelet count below 100,000/mm3) are frequently embedded in the stem.
What to do instead
For every stroke stem, list the checklist before the answer: glucose, blood pressure, platelet count, INR, and the time of onset (or last known well). State the thrombolysis window and the contraindications explicitly, and mention thrombectomy for large-vessel occlusion within the appropriate window. If the glucose is low, treat it and reassess before any thrombolysis decision.
When a stem asks about a drug interaction or a dose adjustment, the candidate answers from the mechanism class ('a beta-blocker') without naming the specific agent's elimination route and without adjusting for renal or hepatic impairment, or ignores the QT-prolonging combination.
Candidates learn drug classes and not individual pharmacokinetics, so they miss that some drugs in a class are renally cleared and others hepatically cleared, and they do not routinely check the eGFR against the drug's renal cutoff. The exam tests the specific drug, the specific organ, and the specific interaction (for example, combining two QT-prolonging agents, or a CYP3A4 inhibitor with a statin).
What to do instead
For every pharmacology stem, state the drug, its elimination route, and the patient's renal and hepatic function, then adjust the dose or choose an alternative. Keep a short list of high-yield interactions (QT prolongation, CYP3A4 inhibition, warfarin with antibiotics, serotonin syndrome, hyperkalemia with ACE inhibitors plus potassium-sparing diuretics) and apply it before answering.