I85PREP
⌘ K
COF study materials
COF study resources

COF practice questions

One question at a time. Build your COF understanding.

First 50 of 200 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.

Continue in the practice tool above to load more questions, 50 at a time.

Question 1General Medical Knowledge

Which vitamin is synthesized in the skin upon exposure to ultraviolet B light?

  1. Vitamin A
  2. Vitamin C
  3. Vitamin D Correct answer.
  4. Vitamin K

Explanation

UVB radiation converts 7-dehydrocholesterol in the epidermis into previtamin D3, which isomerizes to vitamin D3. This is the principal endogenous source of vitamin D in humans.

Question 2General Medical Knowledge

What is the most abundant white blood cell in healthy adult peripheral blood?

  1. Lymphocyte
  2. Neutrophil Correct answer.
  3. Eosinophil
  4. Monocyte

Explanation

Neutrophils typically account for roughly 50-70% of circulating leukocytes in adults. Lymphocytes are the second most common.

Question 3General Medical Knowledge

Which organ is the primary site of drug metabolism via the cytochrome P450 system?

  1. Lung
  2. Liver Correct answer.
  3. Spleen
  4. Kidney

Explanation

Hepatocytes are rich in cytochrome P450 enzymes and carry out most phase I oxidative metabolism. The liver is therefore the principal organ of drug biotransformation.

Question 4General Medical Knowledge

A patient has a blood pressure of 148/94 mmHg on two separate visits. Into which category does this fall?

  1. Stage 2 hypertension
  2. Elevated
  3. Normal
  4. Stage 1 hypertension Correct answer.

Explanation

Stage 1 hypertension is defined as systolic 130-139 or diastolic 80-89; Stage 2 requires systolic at least 140 or diastolic at least 90. A value of 148/94 exceeds both Stage 2 thresholds.

Question 5General Medical Knowledge

Which electrolyte abnormality is most characteristic of primary hyperaldosteronism?

  1. Hyperkalemia
  2. Hypokalemia Correct answer.
  3. Hypercalcemia
  4. Hypophosphatemia

Explanation

Aldosterone promotes sodium reabsorption and potassium excretion in the distal nephron. Excess aldosterone therefore produces hypokalemia along with hypertension.

Question 6General Medical Knowledge

Which pathogen is the most common cause of community-acquired pneumonia in adults?

  1. Mycoplasma pneumoniae
  2. Streptococcus pneumoniae Correct answer.
  3. Haemophilus influenzae
  4. Legionella pneumophila

Explanation

Streptococcus pneumoniae remains the single most frequently identified cause of community-acquired pneumonia in adults. It classically presents with lobar consolidation.

Question 7General Medical Knowledge

Which hormone is produced by the beta cells of the pancreatic islets?

  1. Pancreatic polypeptide
  2. Insulin Correct answer.
  3. Glucagon
  4. Somatostatin

Explanation

Beta cells synthesize and secrete insulin, which lowers blood glucose. Alpha cells produce glucagon, delta cells produce somatostatin, and PP cells produce pancreatic polypeptide.

Question 8General Medical Knowledge

Which blood component is primarily responsible for oxygen transport?

  1. Leukocytes
  2. Platelets
  3. Plasma proteins
  4. Erythrocytes Correct answer.

Explanation

Erythrocytes contain hemoglobin, which binds oxygen in the lungs and delivers it to tissues. The vast majority of blood oxygen is carried by hemoglobin.

Question 9General Medical Knowledge

A patient taking warfarin should be monitored with which laboratory test?

  1. Activated partial thromboplastin time
  2. International normalized ratio Correct answer.
  3. Bleeding time
  4. Thrombin time

Explanation

Warfarin inhibits vitamin K-dependent clotting factors, prolonging the prothrombin time. The INR standardizes this measurement and guides warfarin dosing.

Question 10General Medical Knowledge

Which finding is most consistent with a diagnosis of diabetic ketoacidosis?

  1. pH 7.45, bicarbonate 26 mEq/L
  2. pH 7.38, bicarbonate 24 mEq/L
  3. pH 7.50, bicarbonate 30 mEq/L
  4. pH 7.20, bicarbonate 10 mEq/L, positive serum ketones Correct answer.

Explanation

DKA produces a high-anion-gap metabolic acidosis with low pH, low bicarbonate, and ketonemia. A pH of 7.20 with bicarbonate of 10 and positive ketones fits this pattern.

Question 11General Medical Knowledge

Which medication class acts by inhibiting the sodium-potassium-chloride cotransporter in the loop of Henle?

  1. Potassium-sparing diuretics
  2. Loop diuretics Correct answer.
  3. Carbonic anhydrase inhibitors
  4. Thiazide diuretics

Explanation

Loop diuretics such as furosemide block the NKCC2 cotransporter in the thick ascending limb. This produces the most potent diuretic effect among the classes.

Question 12General Medical Knowledge

A 60-year-old presents with sudden painless loss of vision in one eye. Which diagnosis should be considered first?

  1. Cataract
  2. Open-angle glaucoma
  3. Vitreous hemorrhage from diabetic retinopathy
  4. Central retinal artery occlusion Correct answer.

Explanation

Sudden painless monocular vision loss is a hallmark of central retinal artery occlusion, a vascular emergency. The retina becomes ischemic and vision loss is typically profound and abrupt.

Question 13General Medical Knowledge

Which organism is most commonly associated with peptic ulcer disease?

  1. Helicobacter pylori Correct answer.
  2. Campylobacter jejuni
  3. Escherichia coli
  4. Clostridioides difficile

Explanation

Helicobacter pylori colonizes the gastric mucosa and is a major cause of peptic ulcer disease. Eradication reduces ulcer recurrence.

Question 14General Medical Knowledge

Which of the following best describes the mechanism of action of beta-lactam antibiotics?

  1. Inhibition of bacterial protein synthesis
  2. Inhibition of bacterial DNA gyrase
  3. Inhibition of bacterial cell wall synthesis Correct answer.
  4. Disruption of the bacterial cell membrane

Explanation

Beta-lactams bind penicillin-binding proteins and block peptidoglycan cross-linking, weakening the cell wall. This leads to bacterial lysis, particularly in actively dividing organisms.

Question 15General Medical Knowledge

Which clinical feature most strongly suggests a diagnosis of hypothyroidism?

  1. Tremor with tachycardia
  2. Cold intolerance with weight gain Correct answer.
  3. Diarrhea with hyperreflexia
  4. Weight loss with heat intolerance

Explanation

Hypothyroidism slows metabolism, producing cold intolerance, weight gain, fatigue, and bradycardia. These features reflect reduced thyroid hormone action.

Question 16General Medical Knowledge

Which of the following is the most appropriate initial management for an adult with anaphylaxis?

  1. Intravenous corticosteroids alone
  2. Nebulized albuterol alone
  3. Intramuscular epinephrine Correct answer.
  4. Oral antihistamine

Explanation

Intramuscular epinephrine is the first-line treatment for anaphylaxis and should be given immediately. It reverses bronchospasm and prevents progression of the reaction.

Question 17General Medical Knowledge

Which organism is the leading cause of bacterial meningitis in neonates?

  1. Haemophilus influenzae type b
  2. Streptococcus agalactiae Correct answer.
  3. Streptococcus pneumoniae
  4. Neisseria meningitidis

Explanation

Group B Streptococcus (Streptococcus agalactiae) is a leading cause of neonatal meningitis, acquired during passage through the birth canal. E. coli and Listeria are other important neonatal pathogens.

Question 18General Medical Knowledge

Which electrolyte disturbance is most likely to cause peaked T waves on an ECG?

  1. Hyperkalemia Correct answer.
  2. Hypocalcemia
  3. Hypokalemia
  4. Hypernatremia

Explanation

Hyperkalemia classically produces tall, peaked T waves and can progress to widened QRS complexes and arrhythmias. Potassium shifts across the myocardial membrane alter repolarization.

Question 19General Medical Knowledge

A patient with chronic kidney disease has a low serum calcium and elevated phosphate. Which compensatory mechanism is expected?

  1. Decreased calcitriol production with suppressed PTH
  2. Increased calcitonin secretion
  3. Decreased parathyroid hormone secretion
  4. Increased parathyroid hormone secretion Correct answer.

Explanation

Hyperphosphatemia and reduced calcitriol lower serum calcium, stimulating the parathyroid glands to raise PTH. This secondary hyperparathyroidism is a hallmark of chronic kidney disease.

Question 20General Medical Knowledge

Which of the following best describes the first-pass effect?

  1. Renal excretion of a drug after glomerular filtration
  2. Binding of a drug to plasma albumin
  3. Passive diffusion of a drug across the blood-brain barrier
  4. Drug metabolism by gut and liver before reaching systemic circulation Correct answer.

Explanation

Orally administered drugs absorbed from the gut pass through the portal vein to the liver, where a fraction is metabolized before reaching systemic circulation. This reduces oral bioavailability.

Question 21General Medical Knowledge

Which type of hypersensitivity reaction underlies acute hemolytic transfusion reactions?

  1. Type II Correct answer.
  2. Type IV
  3. Type I
  4. Type III

Explanation

Acute hemolytic transfusion reactions are type II hypersensitivity reactions in which preformed antibodies bind donor red cell antigens and trigger complement-mediated lysis. This produces fever, flank pain, and hemoglobinuria.

Question 22General Medical Knowledge

A patient develops muscle pain and dark urine after starting a statin. Which mechanism best explains this adverse effect?

  1. Inhibition of the sodium-potassium ATPase pump
  2. Blockade of acetylcholine receptors at the neuromuscular junction
  3. Excess calcium deposition in skeletal muscle
  4. Depletion of coenzyme Q10 and myocyte injury Correct answer.

Explanation

Statins inhibit HMG-CoA reductase, reducing synthesis of both cholesterol and coenzyme Q10, a mitochondrial cofactor. The resulting myocyte energy deficit can cause myopathy and rhabdomyolysis.

Question 23General Medical Knowledge

Which of the following is the most sensitive early marker of acute myocardial infarction?

  1. Troponin I Correct answer.
  2. Creatine kinase-MB
  3. Aspartate aminotransferase
  4. Lactate dehydrogenase

Explanation

Cardiac troponins rise within a few hours of myocardial injury and remain elevated for days, making them the preferred biomarker. They are both sensitive and highly specific for cardiac myocyte damage.

Question 24General Medical Knowledge

A patient with a history of gastric bypass surgery presents with confusion, ataxia, and ophthalmoplegia. Which deficiency is most likely?

  1. Iron
  2. Vitamin C
  3. Thiamine Correct answer.
  4. Vitamin B12

Explanation

Thiamine deficiency causes Wernicke encephalopathy, characterized by the triad of confusion, ataxia, and ophthalmoplegia. Patients with malabsorption after bariatric surgery are at particular risk.

Question 25General Medical Knowledge

Which of the following mechanisms best explains the therapeutic effect of ACE inhibitors in heart failure?

  1. Reduction of angiotensin II formation and aldosterone secretion Correct answer.
  2. Inhibition of the sodium-potassium-chloride cotransporter
  3. Blockade of aldosterone receptors in the distal nephron
  4. Direct beta-adrenergic receptor blockade

Explanation

ACE inhibitors block conversion of angiotensin I to angiotensin II, reducing vasoconstriction and aldosterone-mediated sodium retention. This lowers afterload and preload, improving heart failure symptoms.

Question 26General Medical Knowledge

Which vitamin deficiency is most directly associated with prolonged bleeding time due to impaired clotting factor synthesis?

  1. Vitamin C deficiency
  2. Vitamin D deficiency
  3. Vitamin B12 deficiency
  4. Vitamin K deficiency Correct answer.

Explanation

Vitamin K is a cofactor for gamma-carboxylation of clotting factors II, VII, IX, and X, so deficiency impairs their function and prolongs bleeding time. The other vitamins listed do not serve this role in the coagulation cascade.

Question 27General Medical Knowledge

Which class of medication reduces serum LDL cholesterol by inhibiting HMG-CoA reductase?

  1. Fibrates
  2. Niacin
  3. Statins Correct answer.
  4. Bile acid sequestrants

Explanation

Statins inhibit HMG-CoA reductase, the rate-limiting enzyme in hepatic cholesterol synthesis, which lowers intracellular cholesterol and upregulates LDL receptors. This is the defining mechanism of the statin class.

Question 28General Medical Knowledge

A patient is prescribed a medication that is a potent inhibitor of cytochrome P450 3A4. Which consequence is most expected when a drug metabolized primarily by CYP3A4 is co-administered?

  1. Reduced absorption of the substrate drug from the gut
  2. Reduced plasma concentration of the substrate drug
  3. No change because CYP3A4 is not involved in metabolism
  4. Increased plasma concentration of the substrate drug Correct answer.

Explanation

Inhibiting the enzyme that metabolizes a drug slows its clearance, so plasma levels of the substrate rise and toxicity risk increases. This is a classic drug-drug interaction mechanism.

Question 29General Medical Knowledge

Which of the following is the most common cause of nephrotic syndrome in adults?

  1. Membranous nephropathy
  2. Minimal change disease
  3. Focal segmental glomerulosclerosis Correct answer.
  4. IgA nephropathy

Explanation

Focal segmental glomerulosclerosis is the leading cause of nephrotic syndrome in adults, particularly in certain populations. Minimal change disease is more typical in children, while membranous nephropathy and IgA nephropathy have different epidemiologic patterns.

Question 30General Medical Knowledge

A patient with type 1 diabetes develops hypoglycemia after an insulin dose. Which counter-regulatory hormone is released most rapidly to raise blood glucose?

  1. Aldosterone
  2. Insulin
  3. Thyroxine
  4. Glucagon Correct answer.

Explanation

Glucagon is secreted by pancreatic alpha cells in response to falling glucose and stimulates hepatic glycogenolysis and gluconeogenesis. It is the primary rapid counter-regulatory hormone to insulin.

Question 31General Medical Knowledge

Which of the following best describes the primary mechanism by which loop diuretics relieve pulmonary edema?

  1. Increased cardiac contractility
  2. Reduction of intravascular volume through increased renal sodium and water excretion Correct answer.
  3. Direct vasodilation of pulmonary arterioles
  4. Blockade of aldosterone receptors in the collecting duct

Explanation

Loop diuretics inhibit the Na-K-2Cl cotransporter in the thick ascending limb, producing large natriuresis and diuresis that reduces intravascular volume and pulmonary congestion. This volume reduction underlies their efficacy in pulmonary edema.

Question 32General Medical Knowledge

Which of the following findings is most characteristic of acute appendicitis on physical examination?

  1. Pain that is worst in the left lower quadrant
  2. Cullen sign in the periumbilical region
  3. Rebound tenderness at McBurney point Correct answer.
  4. Painless jaundice

Explanation

Appendicitis classically produces tenderness and rebound tenderness at McBurney point in the right lower quadrant as inflammation reaches the parietal peritoneum. This localized peritoneal sign is a hallmark of the diagnosis.

Question 33General Medical Knowledge

A patient with a history of alcohol use disorder presents with confusion, ataxia, and nystagmus. Supplementation of which vitamin is most important to prevent progression of this condition?

  1. Folate
  2. Riboflavin
  3. Vitamin E
  4. Thiamine Correct answer.

Explanation

The presentation suggests Wernicke encephalopathy, caused by thiamine deficiency. Prompt thiamine administration prevents progression to Korsakoff syndrome and is standard practice in at-risk patients.

Question 34General Medical Knowledge

Which of the following is the most appropriate first-line treatment for a patient with newly diagnosed hypertension and no other comorbidities?

  1. A thiazide diuretic, ACE inhibitor, ARB, or calcium channel blocker Correct answer.
  2. A loop diuretic as monotherapy
  3. An alpha-1 antagonist as first-line therapy
  4. A potassium-sparing diuretic alone

Explanation

Guidelines recommend starting with a thiazide diuretic, ACE inhibitor, angiotensin receptor blocker, or calcium channel blocker for uncomplicated hypertension. These classes have outcome data supporting their first-line use.

Question 35General Medical Knowledge

Which of the following is the most common cause of acute pancreatitis in developed countries?

  1. Gallstones Correct answer.
  2. Viral infection
  3. Trauma
  4. Hypertriglyceridemia

Explanation

Gallstones and alcohol are the two leading causes of acute pancreatitis, with gallstones being the most common in many developed populations. Obstruction of the pancreatic duct by a stone triggers enzyme activation and inflammation.

Question 36General Medical Knowledge

A patient on long-term corticosteroid therapy should be monitored for which complication resulting from the drug's mechanism?

  1. Hypoglycemia due to increased insulin sensitivity
  2. Hyperkalemia due to mineralocorticoid excess
  3. Bradycardia due to beta-receptor blockade
  4. Osteoporosis due to suppressed bone formation Correct answer.

Explanation

Glucocorticoids reduce osteoblast activity and impair calcium absorption, leading to bone loss and osteoporosis with chronic use. This is a well-recognized adverse effect requiring monitoring and preventive measures.

Question 37General Medical Knowledge

Which of the following best describes the mechanism by which aspirin exerts its antiplatelet effect?

  1. Irreversible inhibition of cyclooxygenase-1 in platelets Correct answer.
  2. Inhibition of vitamin K-dependent clotting factors
  3. Reversible blockade of ADP receptors on platelets
  4. Activation of antithrombin III

Explanation

Aspirin irreversibly acetylates cyclooxygenase-1 in platelets, blocking thromboxane A2 production for the life of the platelet. This irreversible effect underlies its use in secondary prevention of thrombotic events.

Question 38General Medical Knowledge

A patient presents with a sudden severe headache described as the worst of their life. Which diagnosis should be considered first?

  1. Migraine without aura
  2. Cluster headache
  3. Subarachnoid hemorrhage Correct answer.
  4. Tension headache

Explanation

A thunderclap headache reaching maximum intensity within seconds to minutes is the classic presentation of subarachnoid hemorrhage and requires urgent evaluation, typically with CT and lumbar puncture if needed. Rapid onset and severity distinguish it from primary headache syndromes.

Question 39General Medical Knowledge

Which of the following best explains why aminoglycosides are effective against aerobic gram-negative bacteria but not anaerobes?

  1. They are inactivated by gram-positive cell walls
  2. They bind only to fungal ribosomes
  3. They require low pH for activation
  4. Their uptake requires an oxygen-dependent transport process Correct answer.

Explanation

Aminoglycoside entry into bacteria depends on an oxygen-dependent active transport across the cell membrane, so anaerobic organisms, which lack this process, are intrinsically resistant. Once inside, they bind the 30S ribosomal subunit and disrupt protein synthesis.

Question 40General Medical Knowledge

A patient with a suspected opioid overdose presents with pinpoint pupils and respiratory depression. Which medication is the appropriate antidote?

  1. Naloxone Correct answer.
  2. Atropine
  3. Flumazenil
  4. N-acetylcysteine

Explanation

Naloxone is a competitive opioid receptor antagonist that rapidly reverses opioid-induced respiratory depression and sedation. It is the specific antidote for opioid toxicity.

Question 41Clinical Assessment and Diagnosis

Which term describes the clinician's process of gathering information from the patient and other sources to understand the presenting problem?

  1. Treatment planning
  2. Prognosis
  3. Assessment Correct answer.
  4. Diagnosis

Explanation

Assessment is the broad, ongoing process of collecting data through interviews, observation, and testing. Diagnosis is the classification step that may follow assessment, whereas prognosis and treatment planning come after both.

Question 42Clinical Assessment and Diagnosis

A mental status examination systematically evaluates which of the following?

  1. Occupational and social functioning over the lifespan
  2. Family history and genetic risk
  3. Intelligence quotient and academic achievement
  4. Appearance, mood, thought process, and cognition Correct answer.

Explanation

The mental status examination covers domains such as appearance, behavior, mood and affect, thought content and process, perception, and cognitive function. It is a cross-sectional observation of current functioning.

Question 43Clinical Assessment and Diagnosis

Which type of reliability refers to the consistency of scores when the same test is administered to the same people on two different occasions?

  1. Internal consistency
  2. Test-retest reliability Correct answer.
  3. Split-half reliability
  4. Inter-rater reliability

Explanation

Test-retest reliability indexes stability of scores across time by correlating two administrations of the same measure. Internal consistency and split-half reliability assess agreement among items within a single administration.

Question 44Clinical Assessment and Diagnosis

A test is described as having high validity when it does which of the following?

  1. Measures what it is intended to measure Correct answer.
  2. Produces the same score across repeated administrations
  3. Yields consistent scores across different raters
  4. Contains many items that correlate with one another

Explanation

Validity concerns the accuracy of inferences drawn from scores, that is, whether the instrument measures the construct it claims to measure. The other options describe forms of reliability.

Question 45Clinical Assessment and Diagnosis

In a diagnostic evaluation, a clinician asks a patient to explain the proverb 'people who live in glass houses should not throw stones.' This task primarily probes which ability?

  1. Visuospatial construction
  2. Working memory
  3. Abstract reasoning Correct answer.
  4. Sustained attention

Explanation

Proverb interpretation requires the patient to move from literal wording to abstract meaning, a classic test of abstract reasoning. Impairment here can suggest concrete thinking associated with cognitive or psychotic conditions.

Question 46Clinical Assessment and Diagnosis

Which of the following best describes a structured diagnostic interview?

  1. A brief screening tool completed only by the patient
  2. A free-form conversation in which the clinician follows the patient's lead
  3. A projective technique using ambiguous stimuli to reveal unconscious conflict
  4. A standardized set of questions with specified scoring rules to improve diagnostic consistency Correct answer.

Explanation

Structured interviews standardize the questions asked and the rules for scoring responses, which increases inter-rater reliability of diagnosis. They reduce variability introduced by clinician judgment.

Question 47Clinical Assessment and Diagnosis

The purpose of a screening instrument in clinical assessment is to do which of the following?

  1. Measure change during psychotherapy
  2. Establish a definitive diagnosis
  3. Identify individuals who need further evaluation Correct answer.
  4. Determine the appropriate medication dose

Explanation

Screening tools are designed to be brief and sensitive, flagging people who warrant a fuller diagnostic evaluation. They are not intended to confirm diagnoses on their own.

Question 48Clinical Assessment and Diagnosis

A clinician notes that a patient's speech is rapid, pressured, and difficult to interrupt. This observation is best classified under which area of the mental status examination?

  1. Insight
  2. Speech Correct answer.
  3. Judgment
  4. Thought content

Explanation

Rate, volume, and flow of verbal output are described under the speech domain of the mental status exam. Pressured speech is a classic observation in manic states.

Question 49Clinical Assessment and Diagnosis

Which of the following is the strongest indicator of a clinically significant finding on a screening measure?

  1. The patient's stated preference for a particular diagnosis
  2. A score slightly above the mean for the general population
  3. A single elevated item on the questionnaire
  4. A score in the range designated by validated cutoffs as indicating risk Correct answer.

Explanation

Screening measures are interpreted against empirically derived cutoffs that balance sensitivity and specificity. Scores crossing those thresholds signal the need for further evaluation.

Question 50Clinical Assessment and Diagnosis

A test has high sensitivity but low specificity. What is the most likely consequence when it is used in a general clinic population?

  1. Many true cases will be missed
  2. Many people without the condition will screen positive Correct answer.
  3. The test will be equally accurate in all populations
  4. The test will have high positive predictive value regardless of prevalence

Explanation

Sensitivity is the ability to detect true cases, while specificity is the ability to correctly rule out non-cases. A highly sensitive but poorly specific test produces many false positives.