2001a-Paper 1 – Medical Sciences

A 47-year-old woman with overt thyrotoxicosis is found to have aortic stenosis. Which one of the following features, if present in this woman, is most likely to indicate the need for aortic valve replacement?

The diagram below shows cumulative quantal dose-response curves for a hypothetical drug (drug X). The Y-axis represents the percentage of the population studied who: for curve (a) achieved the desired therapeutic effect at a given dose; and for curve (b) experienced the most important toxic effect at a given dose. Based on this information, the best estimate of the therapeutic index of drug X is approximately:

The alveolar-arterial gradient for oxygen tension in arterial blood (PA-aO2) can be up to 15 mmHg in healthy young adults and as high as 30 mmHg in elderly people. Which one of the following is considered to be the predominant physiological mechanism for a normal PA-aO2?

Significant intercurrent illness is commonly associated with disturbances of thyroid function (sick euthyroid syndrome). Which one of the following is least likely to be present in a euthyroid patient with a severe illness?

At 72 hours following a significant paracetamol overdose, which one of the following tests will allow the best prediction of death or need for liver transplantation?

The most common cause of blindness in elderly Caucasians is:

Graft-versus-host disease is a major complication of allogeneic stem cell transplantation for haematological malignancy in adults. Which one of the following has the least influence on the risk of developing graft-versus-host disease?

Dendritic cells are distinguished by an exceptional ability to carry out which one of the following immune functions?

The most useful investigation for the diagnosis of multiple sclerosis is:

A mutation is located in the middle portion of a double-stranded DNA molecule 200 nucleotides long. At each end of the DNA molecule are sites at which short DNA primers for the polymerase chain reaction (PCR) bind to each strand. In the figures shown below, five possible combinations of primer location and orientation relative to the mutation are shown. In each figure, the long pair of arrows represents the anti-parallel strands of the long DNA molecule and the short arrows represent each short single-stranded DNA primer binding to the closer of the two long strands. The mutation is located at position (II), the primers are located at positions (I) and (III), and the arrowhead on each DNA strand indicates the direction of DNA polymerisation (5’ to 3’). Which one of the following combinations of primer location and orientation is required to amplify the mutation by PCR?

A number of patients in a ward have been found to be colonised with vancomycin-resistant enterococci. What would be the best laboratory test to determine if transmission from one patient to another has occurred?

A 35-year-old woman with hypertrophic cardiomyopathy presents with chest pain and palpitations. Her heart rate is 155/minute and irregular, and her blood pressure is 130/80 mmHg. What is the most appropriate initial therapy?

In a patient with cryptogenic fibrosing alveolitis (idiopathic pulmonary fibrosis), the finding on bronchoalveolar lavage of an elevated proportion of which one of the following cell types is associated with a better response to therapy?

A bioavailability study has been performed to compare a proposed new generic capsule, in a strength of 50 mg, with a marketed tablet preparation in a strength of 100 mg. The active ingredient is a drug with linear kinetics. A cross-over design was used, with each subject receiving, in random order and with an adequate wash-out period, a single oral dose of one tablet on one occasion and one capsule on the other. The mean results for the area under the plasma concentration versus time curve (AUC) are 300 mg.h/L for the capsule, and 500 mg.h/L for the tablet. The best estimate of the relative bioavailability of the capsule with respect to the tablet is:

A 25-year-old woman presents to the emergency department with renal colic and macroscopic haematuria. She reports having had several previous episodes treated at another hospital. The least likely diagnosis is:

The COX-2 isoform of cyclo-oxygenase is most strongly expressed in which one of the following tissues?

Which one of the following is the most potent inhibitor of aldosterone secretion in a healthy individual?

A 45-year-old man develops stage C cancer of the caecum. There is a strong family history of bowel cancer in the absence of polyps and there is no history of colitis. The most likely underlying inherited genetic abnormality is in:

A 19-year-old woman presents with recent-onset of right leg swelling and pleuritic chest pain and is found to have iliofemoral thrombosis on Doppler ultrasound examination. Results of a ventilation-perfusion lung scan indicate a high probability for pulmonary emboli. She had been taking the oral contraceptive pill for the last three years but has now ceased. She is a non-smoker. There is no significant medical history and no known family history of venous thromboembolism. Which one of the following investigations for an underlying hypercoagulable state is most likely to be affected by the presence of the extensive thrombosis?

Which one of the following is associated with the highest risk of NSAID (non-steroidal anti-inflammatory drug)-induced gastric ulceration?

T lymphocytes expressing both CD4 and CD8 on the cell surface are most likely to be found in which one of the following anatomical locations in healthy individuals?

In treating constipation, which one of the following agents administered over an extended period of time is most likely to lose its effectiveness?

An 18-year-old woman presents with a two-week history of cervical lymphadenopathy, fever, fatigue and myalgia. A Paul-Bunnell test (heterophile antibody) has been negative on two occasions, a week apart. Full blood examination reveals a lymphocytosis with many atypical lymphocytes. The most likely diagnosis is acute:

The picture below shows a computed tomography (CT) scan of the heart. Which one of the following is the most likely diagnosis?

Vertigo which occurs with neck extension is most likely due to:

Allopurinol precipitates azathioprine toxicity by which one of the following mechanisms?

Which one of the following mutations in a gene is most likely to disrupt the production of a protein?

In a patient with a severe exacerbation of asthma, the use of a peak-flow meter may underestimate the severity of airflow limitation compared to the use of spirometry and measurement of the forced expiratory volume in 1 second (FEV1). Which one of the following is mainly responsible for this reduction in the accuracy of the peak-flow meter?

The most important rationale for using adjuvant chemotherapy soon after surgery for cancer (rather than deferring chemotherapy until the cancer has recurred) is that after surgery:

Which one of the following is the best predictor of outcome in a patient with colorectal cancer?

A 32-year-old woman, who has recently migrated from India, is breastfeeding her third child and presents with lethargy and a history of recurrent chest infection. She has a vegetarian diet. Physical examination shows her to be anaemic with no site of blood loss clinically evident and no other abnormalities. Investigations show: Full blood count haemoglobin 64 g/L [120-155] mean corpuscular volume (MCV) 68 fL [80-95] white cell count 7.4 x 109/L [3.5-9.5] differential normal platelet count 412 x 109/L [130-330] Blood film is shown below. With respect to the patient’s anaemia, which one of the following laboratory results has the most diagnostic value?

A 28-year-old woman presents with galactorrhoea. She has been treated for hypothyroidism for five years with thyroxine 0.1 mg/day. She is also receiving lithium carbonate for depression and her serum lithium levels are in the mid-therapeutic range. She takes diazepam 5 mg nocte for insomnia and metoclopramide 10 mg as required for nausea. Her serum prolactin concentration is 1800 mU/L [<600]. From this history, which one of the following factors is most likely to be responsible for her hyperprolactinaemia and galactorrhoea?

In renal transplant biopsies, which one of the following features of acute rejection has the worst prognostic implication?

Which one of the following biologically active components of the complement cascade is most directly responsible for the formation of transmembrane channels leading to cell lysis?

Which one of the following is the most common association of the abnormality shown in the X-ray above?

A young man presents with breathlessness and ankle swelling. He had a ventricular septal defect (VSD) repaired at the age of three years. He is centrally cyanosed and has a prominent right ventricular heave on palpation of the chest. The most likely finding is:

The principal aim of a phase 1 trial of a cytotoxic agent is to:

A 67-year-old woman with severe chronic obstructive pulmonary disease undergoes an all-night respiratory sleep study. The study reveals no evidence of obstructive sleep apnoea but there are three periods of repeated falls in oxyhaemoglobin saturation (SaO2). Which one of the following is the most likely explanation for the falls in SaO2?

Which one of the following is the strongest independent risk factor for stroke?

The diagram below shows cumulative quantal concentration-response curves for a hypothetical drug (drug X) which has linear kinetics. The Y-axis represents the percentage of the population studied who: for curve (a) achieved the desired therapeutic effect at a given plasma concentration; and for curve (b) experienced the most important toxic effect at a given plasma concentration. If a patient with no evidence of toxicity who has not achieved the desired therapeutic response has a measured concentration of 40 mg/L, the best response would be to:

A patient undergoes a Schilling test because of vitamin B12 deficiency. The following results are obtained: The most likely pathology is:

Which one of the following antibiotics is least active against pathogenic anaerobic bacteria (e.g. Bacteroides fragilis, Clostridium perfringens)?

A 22-year-old woman has been on a stable dose of anticonvulsant for three years. She has recently experienced difficulties in seeing at night. A formal ophthalmological assessment demonstrates visual field constriction. For which one of the following anticonvulsants is it important to monitor visual fields?

A 64-year-old woman undergoes a dual-energy X-ray absorptiometry scan. The report is shown below. According to World Health Organisation (WHO) definitions, the patient's lumbar spine bone density is:

A 48-year-old previously well man is receiving a transfusion of four units of packed red cell concentrate via a peripheral intravenous line after presenting with melaena secondary to a bleeding duodenal ulcer. He has not been previously transfused. Admission biochemistry (including urea, electrolytes and creatinine) is normal and pre-transfusion blood counts are normal apart from anaemia (haemoglobin 64 g/L [135-170]). Less than five minutes after transfusion of the third unit of blood is commenced, he complains of feeling very unwell and abruptly develops fever, chills, rigors and profound hypotension. In the absence of ABO, Rhesus or minor blood group donor-recipient incompatibility, the most likely diagnosis is:

The following pharmacokinetic data (normalised to a 70 kg individual) are provided for five drugs. Which one of the following drugs is most likely to have the slowest rate of clearance from plasma?

A non-consanguineous family with a rare genetic disease has been identified. The pedigree is shown below. What is the most likely mode of inheritance?

Which one of the following findings during a stress exercise ECG test is most predictive of angiographically significant multivessel or left main coronary artery disease?

At the onset of infection or inflammation, the level of which one of the following acute phase proteins rises most rapidly and by the highest percentage over background?

A 40-year-old woman presents with progressive breathlessness on exertion. She is a non-smoker. Physical examination and chest X-ray reveal no significant abnormality. Pulmonary function tests show the following results: Which one of the following is the most likely explanation for this woman's pulmonary function test results?

For an 82-year-old nursing home resident who experiences recurrent falls, which one of the following is least likely to prevent hip fracture?

The manometric feature most characteristic of achalasia is:

Cytokine regulation (especially involving interleukin 2) is least affected by which one of the following immunosuppressive drugs?

The mechanism of penicillin resistance in pneumococcal infections is most likely to be due to which one of the following?

The most important application of carcinoembryonic antigen (CEA) measurements in patients with colon cancer is:

In complex partial seizures of temporal lobe type, the most common finding at surgery for the epilepsy is:

The diagram below shows the relationship between the plasma concentration of a drug and the effect of that drug over time in a single individual given one dose of the drug. The direction of change over time is shown by the arrows. The relationship is described by an anti-clockwise hysteresis loop. The numbers on the loop indicate the number of hours after the dose was given. The best explanation of this phenomenon is that:

Genetically determined variation in which one of the following cell surface molecules is capable of conferring the greatest resistance to human immunodeficiency virus (HIV) infection?

Deficiency of which one of the following enzymes is most likely to cause severe hyperuricaemia?

Which one of the following physical findings would be least expected in association with the chest X-ray shown above?

Which feature of glomerular pathology is least consistent with the diagnosis of Wegener's granulomatosis?

A 62-year-old man on weekly oral methotrexate for psoriatic arthritis inadvertently receives a course of oral trimethoprim-sulfamethoxazole therapy for urinary infection. He becomes ill with mucositis, fever and bruising and is found to have moderately severe pancytopenia. Folinic acid (in the form of calcium folinate) is administered intravenously as an antidote for presumed methotrexate toxicity. The principal mode of action of folinic acid is:

A young woman presents with thirst and polyuria. Following overnight water deprivation, which one of the following is the best indicator that she has partial (and central) diabetes insipidus rather than psychogenic polydipsia?

In the pedigree shown below, the man indicated by an arrow has been shown to have an autosomal recessive biochemical disorder with complete penetrance. The causative gene has not been identified. His parents are obligate carriers and do not exhibit any biochemical abnormalities. His sister also has normal biochemical studies. The carrier frequency in this population is 10%. In the absence of consanguinity, what is the risk of the sister having a child with the biochemical abnormality?

In a patient with oropharyngeal dysphagia following a stroke, which one of the following would be the strongest indicator of increased risk of aspiration?

Which one of the following pharmacokinetic parameters is most important in the optimal prescribing of beta-lactam antibiotics?

Drug X is given intravenously, using two different regimens, to the same patient on two different occasions. On both occasions, there is no measurable amount of the drug in plasma prior to its administration. On both occasions, the volume of distribution of X is 0.85 L/kg and the plasma half-life is six hours. Regimen A: continuous intravenous infusion of 10 mg/kg/h, with no loading dose. Regimen B: a loading dose of 50 mg/kg given rapidly intravenously, then a continuous intravenous infusion of 10 mg/kg/h. Using Regimen A, the plasma concentration of X after 48 hours was 100 mg/L. Using Regimen B, the plasma concentration of X after 48 hours would most closely approximate:

A 25-year-old man dislocates his right shoulder while playing football. This is reduced in the emergency department and he is discharged after observation. After removal of his sling he has problems with abduction of the arm. Examination shows weakness of abduction at the shoulder and sensory loss on the lateral aspect of his upper arm. The nerve involved is the:

In a randomised controlled trial of an intervention to stop smoking in patients with chronic obstructive pulmonary disease (COPD), the use of an intention-to-treat analysis is most likely to cause which one of the following?

Which one of the following histopathological features is least likely to be seen in cranial (temporal) arteritis?