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1. General Principles & Basic Science MCQs

Practice Set 49 of 789

This practice set contains high-yield board review questions covering key concepts in 1. General Principles & Basic Science. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 961

Topic: 1. General Principles & Basic Science
A 17-year-old woman presents with a dry cough and pyrexia, some 3 weeks after induction therapy for acute lymphoblastic leukaemia. She has been treated with a macrolide and co-amoxiclav by her GP but there has been no response. On examination she is pyrexial 38.2 °C and short of breath at rest. There are scattered crackles throughout both lung fields on auscultation. Investigations: Hb 12.3 g/dl, WCC 9.1 × 10^9/l, PLT 155 × 10^9/l, Na+ 138 mmol/l, K+ 4.2 mmol/l, Creatinine 102 μmol/l, LDH 420 U/l, CXR diffuse bilateral infiltrates extending from the perihilar region, pH 7.36, pO2 9.8 kPa, pCO2 4.7 kPa. Which of the following is the most likely diagnosis?
. CMV pneumonitis
. Fungal pneumonitis
. Klebsiella pneumoniae
. Leukaemic infiltration
. Pneumocystis jirovecii

Correct Answer & Explanation

. Pneumocystis jirovecii

Explanation

The pattern of diffuse pulmonary infiltrates coupled with mild hypoxia fits best with Pneumocystis jirovecii. The chest radiograph appearances described are classical for Pneumocystis jirovecii pneumonia.

Question 962

Topic: Infection, Pharmacology & VTE
You are asked to see a 57-year-old smoker, who complains of shortness of breath some 7 days after a total hip replacement. On examination, he is obese and has a swollen left leg. He is also visibly short of breath. There appears to be increased prominence of vascular markings at the right hilum on the chest X-ray. His calculated alveolar–arterial (A–a) gradient is 34 mmHg (10-24 normal range). Which of the following fits best with his diagnosis?
. Atelectasis
. Hyperventilation syndrome
. Pneumothorax
. Post-operative pneumonia
. Pulmonary embolus

Correct Answer & Explanation

. Pulmonary embolus

Explanation

The alveolar–arterial (A–a) gradient is affected primarily by ventilation/perfusion (V/Q) mismatch and shunting. Pulmonary embolus is the most likely diagnosis given the clinical presentation of a swollen leg (DVT) and shortness of breath post-surgery.

Question 963

Topic: 1. General Principles & Basic Science

A 26-year-old male smoker presents to the Emergency Department with sudden onset of left-sided pleuritic chest pain and breathlessness. He takes no regular medication and has not received a diagnosis of significant chest disease. A chest X-ray confirms the clinical suspicion of a left sided pneumothorax with a 2.5cm rim of air. What should the initial management of his pneumothorax be?

. 100% inspired oxygen
. Aspiration
. Conservative treatment
. Intercostal tube drainage
. Surgical referral for pleurodesis

Correct Answer & Explanation

. Aspiration

Explanation

Correct Answer: B- Aspiration Explanation Aspiration The immediate management of a spontaneous primary pneumothorax >2cm is air aspiration. 100% inspired oxygen 100% inspired oxygen is incorrect. High-flow oxygen is helpful regardless of a patient’s oxygen saturations in pneumothorax as it aids resolution of the pneumothorax; however, 100% oxygen is not required. The correct initial management is aspiration. Conservative treatment Conservative treatment is incorrect. In a young, stable patient conservative management can be considered if the pneumothorax is small (rim of air is < 2 cm at level of hilum). Intercostal tube drainage Intercostal tube drainage is incorrect. Intercostal tube drainage should be reserved for patients who fail to respond to aspiration or who have a tension pneumothorax. Surgical referral for pleurodesis Surgical referral for pleurodesis is incorrect. Surgical referral is considered in patients who develop complications of their pneumothorax (ie bronchopleural fistula) or who have had more than one pneumothorax.

Question 964

Topic: 1. General Principles & Basic Science
A 75-year-old woman visits your chronic obstructive pulmonary disease (COPD) clinic for review. Her blood gases were checked at her last visit 2 months ago when she was relatively well, and you check them again today. Her PaO2 on air on both occasions was 6.8 kPa. There is no CO2 retention on 28% O2. To her credit, she did succeed in stopping smoking 6 months ago. She is maintained on combination inhaled steroid and long-acting β2-agonist therapy. What is the next management step most likely to improve her prognosis?
. Add in an anticholinergic to her therapy
. Continue her current treatment and review in 4 months’ time
. Give her rotational antibiotics to prevent an exacerbation
. Offer her oxygen cylinders for use as required
. Suggest she uses an oxygen concentrator for at least 15 hours a day

Correct Answer & Explanation

. Suggest she uses an oxygen concentrator for at least 15 hours a day

Explanation

Studies have shown that at least 15 hours of oxygen therapy per day is required to reduce the pulmonary hypertension associated with COPD, treat the underlying pathology of incipient right heart failure, and improve survival.

Question 965

Topic: 1. General Principles & Basic Science
A 67-year-old man consults his doctor complaining of a painful mouth and increasing difficulty eating. He has a past history of smoking and has chronic obstructive pulmonary disease (COPD). His medication history includes use of a fluticasone/salmeterol combination inhaler and omeprazole for indigestion. On examination he has a body mass index (BMI) of 29 kg/m2 and looks well. There is extensive stomatitis and pharyngitis on examination of the oropharynx, with white plaques on examination of the tongue. Full blood count, U&Es, liver function tests (LFTs) and viscosity are all normal. Which of the following would be the most appropriate management in this case?
. Advise him to rinse his mouth each time he uses his inhaler and use a spacer device and review him in a month
. Arrange urgent barium swallow
. Arrange an urgent upper gastrointestinal endoscopy
. Increase his dose of omeprazole
. Stop his inhaled steroids

Correct Answer & Explanation

. Advise him to rinse his mouth each time he uses his inhaler and use a spacer device and review him in a month

Explanation

This man almost certainly has oropharyngeal and oesophageal candidiasis from inadequate hygiene after using his inhaler. He should be taught adequate inhaler technique and urged to rinse his mouth after each use. Resistant symptoms can be managed with oral nystatin or a course of fluconazole.

Question 966

Topic: 1. General Principles & Basic Science

A 58-year-old man is referred by his GP with probable obstructive sleep apnoea (OSA). Which of the following features is most strongly associated with OSA?

. Body mass index of 26 kg/m2
. Daytime somnolence
. Epworth sleepiness score of 6
. Normal blood pressure
. Normal oxygen saturations at night

Correct Answer & Explanation

. Daytime somnolence

Explanation

Correct Answer: B- Daytime somnolence Explanation Daytime somnolence Daytime somnolence is the predominant symptom of OSA. Body mass index of 26 kg/m2 Body mass index of 26 kg/m2 is incorrect. Obstructive sleep apnoea is associated with obesity (of which hypothyroidism is a cause) and sedatives such as alcohol. Epworth sleepiness score of 6 Epworth sleepiness score of 6 is incorrect. The Epworth sleepiness score can be between 0 and 24 (the higher the score, the more sleepy the patient is) and 6/24 is low. A score of 11 or more is suggestive of OSA. Normal blood pressure Normal blood pressure is incorrect. OSA is associated with hypertension. Normal oxygen saturations at night Normal oxygen saturations at night is incorrect. OSA results in repeated oxygen desaturations overnight. The disorder is most marked during rapid eye movement (REM) sleep.

Question 967

Topic: Physiology & Rehabilitation

A 55-year-old man presents with increasing shortness of breath. He has been working in the sand- blasting industry and exposed to quartz particles. What is the most likely diagnosis?

. Asbestosis
. Asthma
. Eosinophilic pneumonitis
. Sarcoidosis
. Silicosis

Correct Answer & Explanation

. Silicosis

Explanation

Correct Answer: E- Silicosis Explanation Silicosis Silicosis is a fibrotic disease of the lungs caused by inhalation of crystalline silicon dioxide, usually in the form of quartz. Silicosis can affect anyone involved in quarrying, carving, mining, tunnelling, grinding or sand- blasting, if the dust generated contains quartz. Between 50 and 60 cases are diagnosed in the UK each year, generally in people involved in the production of slate or granite, among miners cutting through rock and in fettlers in foundries. Crystalline silica is present in the earth’s crust usually as quartz, although other forms such as crystobalite and tridymite occur occasionally. They are all extremely toxic to macrophages. Quartz seems to be most toxic when freshly fractured, suggesting that its surface properties are important in toxicity. Silicosis presents a spectrum of clinical appearances, depending on the circumstances in which it is contracted. The most severe form is acute silicosis, which can be acquired after very heavy exposure over just a few months, such as during a sand-blasting job without respiratory protection. These patients become intensely breathless and die within months. The X-ray shows appearances resembling pulmonary oedema. Less heavy exposure causes progressively less dramatic symptoms, ranging from a progressive upper lobe fibrosis with slowly increasing exertional dyspnoea over several years (accelerated silicosis) to a condition with radiographic nodular changes similar to coal-worker’s pneumoconiosis (simple nodular silicosis) that is unassociated with any symptoms or physical signs. This last type of silicosis is the most common, and is usually associated with exposure to dust containing 10–30% silica over a prolonged period. Simple nodular silicosis differs from coal-worker’s pneumoconiosis in that the lesions tend to be larger (3–5 mm) and in that it is progressive even after dust exposure ceases. Lesions increase in size and become more profuse. Moreover, extensive simple silicosis can be associated with some restriction of lung volumes. Accelerated silicosis and progressive massive fibrosis cause lung restriction and lead to cor pulmonale and cardiorespiratory failure. Asbestosis Asbestosis is incorrect. Asbestosis can develop following exposure to asbestos fibres. Typical occupations associated with possible exposure include plumbers, electricians, engineers and ship dockyard workers. Asthma Asthma is incorrect. The short history given alludes to an occupation-related cause of breathlessness. The specific mentioning of quartz particles suggests a diagnosis of silicosis. Asthma is not an occupation-related lung disease. Eosinophilic pneumonitis Eosinophilic pneumonitis is incorrect. The short history given alludes to an occupation-related cause of breathlessness. The specific mentioning of quartz particles suggests a diagnosis of silicosis. Eosinophilic pneumonitis is not an occupation-related lung disease. Sarcoidosis Sarcoidosis is incorrect. The short history given alludes to an occupation-related cause of breathlessness. The specific mentioning of quartz particles suggests a diagnosis of silicosis. Sarcoidosis is not an occupation- related lung disease.

Question 968

Topic: 1. General Principles & Basic Science
A 50-year-old patient presents with blood eosinophilia in association with a radiographic pulmonary infiltrate. A bronchoscopy shows an excess of eosinophils in bronchoalveolar lavage fluid in the absence of pathogenic micro-organisms. The diagnosis of eosinophilic pneumonia is made. What is the best treatment apart from removing the causal factors?
. Clarithromycin
. Inhaled β2-agonists
. Leukotriene-receptor antagonists
. Nebulised β2-agonists
. Systemic steroids

Correct Answer & Explanation

. Systemic steroids

Explanation

Correct Answer: Systemic steroids. Eosinophilic pneumonia often responds well to corticosteroid medication, although treatment might need to be prolonged (6 months or more) in patients with the chronic forms of the disorder. The importance of identifying whether it is associated with causal factors (such as parasitic infestation, drugs, asthma, or vasculitis) lies in the need to manage these specifically.

Question 969

Topic: 1. General Principles & Basic Science

What would the optimal management be for a 70-year- old man with moderate chronic obstructive pulmonary disease (COPD) who has attended the Emergency Department with increasing dyspnoea and who has been found to have a 3 cm pneumothorax?

. Chest drain insertion if needle aspiration fails
. Chest drain insertion initially
. Conservative management, with observation and repeat chest X-ray after 4 hours
. Conservative management, with observation and repeat chest X-ray after 12 hours
. Needle aspiration

Correct Answer & Explanation

. Chest drain insertion initially

Explanation

Correct Answer: B- Chest drain insertion initially Explanation Chest drain insertion initially This is a man with a pneumothorax secondary to his COPD. He is symptomatic and the British Thoracic Society (BTS) Guidelines suggest he should not undergo needle aspiration but proceed to chest drain insertion initially, given the rim of the pneumothorax is > 2 cm and he is breathless. Chest drain insertion if needle aspiration fails Chest drain insertion if needle aspiration fails is incorrect. This is appropriate management of a primary pneumothorax > 2 cm. Conservative management, with observation and repeat chest X-ray after 4 hours Conservative management, with observation and repeat chest X-ray after 4 hours is incorrect. Pneumothoraces with a > 2 cm rim should be actively treated with either aspiration (in primary pneumothoraces) or chest drain insertion (secondary pneumothoraces). Conservative management, with observation and repeat chest X-ray after 12 hours Conservative management, with observation and repeat chest X-ray after 12 hours is incorrect. Conservative management is appropriate for primary pneumothoraces if the rim is < 2 cm and the patient is not breathless. For secondary pneumothoraces, conservative management with admission for high-flow oxygen and observation for 24 hours is appropriate if the rim is < 1 cm and the patient is not breathless. Needle aspiration Needle aspiration is incorrect. Needle aspiration is considered as first-line management in secondary pneumothoraces of 1–2 cm in a patient who is not breathless. In primary pneumothoraces, needle aspiration is appropriate first-line management if the patient is breathless or the rim is > 2 cm.

Question 970

Topic: 1. General Principles & Basic Science

A diagnostic test has a fixed sensitivity and specificity. If the prevalence of the target disease in the tested population decreases, what is the effect on the predictive values of the test?

. Positive predictive value increases, negative predictive value increases
. Positive predictive value decreases, negative predictive value increases
. Positive predictive value decreases, negative predictive value decreases
. Positive predictive value increases, negative predictive value decreases
. Both positive and negative predictive values remain unchanged

Correct Answer & Explanation

. Positive predictive value decreases, negative predictive value increases

Explanation

As disease prevalence decreases, the absolute number of true positives decreases while false positives increase, thus decreasing the positive predictive value (PPV). Conversely, true negatives increase, which increases the negative predictive value (NPV).

Question 971

Topic: Biomechanics & Biomaterials

Failure of a modular total hip arthroplasty at the head-neck junction often involves crevice corrosion. Which of the following initiates this specific type of corrosion in orthopedic implants?

. Galvanic differences between identical metals
. Systemic depletion of circulating macrophages
. Localized depletion of oxygen within the crevice
. Mechanical fracture of the ceramic head
. Excessive production of highly alkaline synovial fluid

Correct Answer & Explanation

. Localized depletion of oxygen within the crevice

Explanation

Crevice corrosion is initiated by the localized depletion of oxygen within the fluid restricted inside the crevice. This creates an anodic, acidic environment compared to the oxygen-rich surface outside, driving metal dissolution.

Question 972

Topic: Biology, Genetics & Bone Healing

Which of the following correctly pairs the receptor and its specific cellular location during the physiological process of osteoclast activation?

. RANKL on the osteoclast surface
. RANK on the osteoclast surface
. Osteoprotegerin (OPG) on the osteoclast surface
. Macrophage colony-stimulating factor (M-CSF) on the osteoblast
. RANK on the osteoblast surface

Correct Answer & Explanation

. RANK on the osteoclast surface

Explanation

Receptor Activator of Nuclear factor Kappa-B (RANK) is located on the surface of osteoclasts and their precursors. Its ligand, RANKL, is expressed on the surface of osteoblasts and stromal cells.

Question 973

Topic: 1. General Principles & Basic Science

In a clinical trial evaluating a novel fracture fixation device, investigators conclude there is no difference in union rates compared to standard plating (p = 0.15). However, a true difference exists in the population, representing a Type II error. Which parameter is mathematically defined as 1 minus the probability of a Type II error?

. Alpha level
. P-value
. Statistical power
. Confidence interval
. Odds ratio

Correct Answer & Explanation

. Statistical power

Explanation

Statistical power is defined as the probability of correctly rejecting the null hypothesis when it is false. It is mathematically calculated as 1 minus Beta (the probability of committing a Type II error).

Question 974

Topic: Biomechanics & Biomaterials

On a standard stress-strain curve representing the mechanical behavior of cortical bone, what does the slope of the linear elastic region represent?

. Yield strength
. Ultimate tensile strength
. Toughness
. Young's modulus of elasticity
. Viscoelasticity

Correct Answer & Explanation

. Young's modulus of elasticity

Explanation

The slope of the linear elastic region on a stress-strain curve represents Young's modulus of elasticity. This value denotes the intrinsic stiffness of the material.

Question 975

Topic: Surgical Anatomy & Approaches

A 28-year-old athlete sustains a traction injury to the brachial plexus. Examination reveals profound weakness in shoulder abduction and external rotation, but normal internal rotation and adduction. Sensation is diminished over the lateral deltoid. Which neural structure is most likely injured?

. Upper trunk (C5-C6)
. Middle trunk (C7)
. Lower trunk (C8-T1)
. Posterior cord
. Medial cord

Correct Answer & Explanation

. Upper trunk (C5-C6)

Explanation

The clinical picture describes Erb's palsy, caused by an injury to the upper trunk of the brachial plexus (C5-C6). This affects the suprascapular, axillary, and musculocutaneous nerves, leading to loss of abduction and external rotation.

Question 976

Topic: 1. General Principles & Basic Science

An orthopaedic surgeon identifies 100 patients who developed a deep surgical site infection following spine surgery and compares them to 300 similar patients who did not develop an infection. The surgeon retrospectively reviews their charts to determine the frequency of poorly controlled diabetes in each group. What type of study design is this?

. Prospective cohort study
. Retrospective cohort study
. Case-control study
. Cross-sectional study
. Randomized controlled trial

Correct Answer & Explanation

. Case-control study

Explanation

This is a case-control study. The investigator groups patients based on the outcome (infection vs. no infection) first, and then looks backward to assess for prior exposure (diabetes).

Question 977

Topic: Infection, Pharmacology & VTE

A 70-year-old female is recovering from a total knee arthroplasty. On post-operative day 5, she develops a confirmed deep vein thrombosis and her platelet count drops from 250,000 to 90,000. She is currently on subcutaneous unfractionated heparin. What is the most appropriate immediate pharmacological management?

. Stop heparin and start low-molecular-weight heparin (LMWH)
. Stop heparin and start warfarin immediately
. Stop heparin and start a direct thrombin inhibitor like argatroban
. Continue heparin and transfuse platelets
. Insert an inferior vena cava filter and observe without anticoagulation

Correct Answer & Explanation

. Stop heparin and start a direct thrombin inhibitor like argatroban

Explanation

The patient has developed heparin-induced thrombocytopenia (HIT). All heparin products (including LMWH) must be stopped immediately, and anticoagulation should be continued with a non-heparin agent such as a direct thrombin inhibitor (e.g., argatroban) or fondaparinux.

Question 978

Topic: Biology, Genetics & Bone Healing

A 55-year-old woman with a history of celiac disease presents with diffuse bone pain. Radiographs demonstrate bilateral symmetrical pseudofractures (Looser zones) in the femoral neck. Laboratory tests reveal hypocalcemia, hypophosphatemia, and elevated alkaline phosphatase. What is the most likely diagnosis?

. Osteoporosis
. Paget's disease
. Osteomalacia
. Primary hyperparathyroidism
. Renal osteodystrophy

Correct Answer & Explanation

. Osteomalacia

Explanation

The presence of Looser zones (pseudofractures) combined with hypocalcemia, hypophosphatemia, and elevated alkaline phosphatase is the classic biochemical and radiographic profile of osteomalacia, often driven by severe Vitamin D deficiency.

Question 979

Topic: Infection, Pharmacology & VTE

A 29-year-old male with sickle cell disease presents with acute osteomyelitis of the humeral diaphysis. While Staphylococcus aureus is the most common organism overall, which of the following organisms is disproportionately responsible for osteomyelitis in this specific patient population?

. Streptococcus pyogenes
. Pseudomonas aeruginosa
. Salmonella typhimurium
. Haemophilus influenzae
. Neisseria gonorrhoeae

Correct Answer & Explanation

. Salmonella typhimurium

Explanation

Patients with sickle cell disease have a uniquely high risk for Salmonella osteomyelitis due to autosplenectomy, microinfarcts in the bowel leading to bacteremia, and expansion of the medullary space.

Question 980

Topic: 1. General Principles & Basic Science

In skeletal muscle physiology, the initiation of contraction occurs when intracellular calcium levels rise. To which specific molecular structure does calcium directly bind to facilitate the cross-bridge cycle?

. Myosin heavy chain
. Tropomyosin
. Actin binding site
. Troponin C
. Sarcoplasmic reticulum

Correct Answer & Explanation

. Troponin C

Explanation

Calcium released from the sarcoplasmic reticulum binds directly to Troponin C. This binding causes a conformational change that moves tropomyosin away from the myosin-binding sites on the actin filament, allowing contraction to occur.

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