2005a_Paper 1 – Medical Sciences

A study is comparing the bioavailability of a new oral preparation of a drug (100 mg tablet) with the marketed intravenous preparation (50 mg in 2 mLs). In this crossover study, healthy volunteers were given in random order one 100 mg tablet or 50 mg intravenously (IV). The drug has linear kinetics within the range of concentrations studied. The mean results are as follows: Which of the following is the best estimate of the oral bioavailability of the tablet?

Which one of the following is the predominant stimulus to gastric acid secretion in a healthy individual?

With which of the following viruses is cancer of the cervix most strongly associated?

Diabetic neuropathic arthropathy is most likely to affect which of the following areas?

In a patient with IgA nephropathy who has a serum creatinine in the normal range, which of the following is the best predictor of developing end-stage renal failure?

Which of the following mechanisms best describes the mode of action of the sulphonylurea class of drugs?

The relationship of the left ventricular pressure to volume throughout a single cardiac cycle (Pressure-Volume Loop) is recorded on two occasions in an intact anaesthetised animal, before (control) and during an intravenous infusion of a pharmacological agent (treatment). The results are shown below. Which of the following agents is most likely to have been infused?

Headache, blindness and jaw claudication secondary to end-organ ischaemia are common clinical manifestations of temporal arteritis (giant cell arteritis). Which of the following most accurately describes the common pathophysiologic mechanism of end-organ ischaemia in this condition?

Which of the following transfusion-related events is most frequently reported (episodes/unit transfused) with transfusion of unmodified red cells?

Which of the following anticonvulsant drugs is most likely to cause weight gain in young women?

The mechanism by which specific information encoded by viral DNA is transferred to messenger RNA (mRNA) is:

Which intervention has been best demonstrated to extend maximal life span in animals?

In patients with a certain genetic disorder, more than 95% of the abnormal genes have the same mutation. Analysis of a highly polymorphic locus in an intron of the gene shows similar allele frequencies in patients as in the general population. Which one of the following genetic mechanisms is least likely to account for the predominance of one mutation in patients with this disorder?

A 60-year-old male presents with worsening dysphagia for solid and liquid food. Manometry is shown above (reference normal on left, patient tracing on right). The most likely diagnosis is:

A 58-year-old male is referred with breathlessness on exercise. He has smoked 20 cigarettes/day since the age of 13. He completed his electrician's apprenticeship at a naval dockyard, and worked in the construction industry until sustaining a back injury and retiring at the age of 50 years. A chest X-ray is reported as abnormal and a thoracic computed tomography (CT) scan (shown opposite) is performed. The CT scan appearances are most characteristic of which one of the following conditions?

A test has a sensitivity of 95% and a specificity of 90%. It is used to screen the general population for a rare condition that has a prevalence of 1 in 100,000. What will the positive predictive value be nearest to?

In addition to decreased gastrointestinal calcium absorption, by which of the following mechanisms is prednis(ol)one most likely to cause net bone loss in a 65-year-old man?

A 67-year-old woman develops symptomatic anaemia and jaundice nine days after subtotal colectomy for adenocarcinoma of the colon, at the time of which she received a transfusion of 3 units of red cells. She is on therapy (which includes sulfasalazine) for ulcerative colitis. Review of the pre-operative antibody screen shows this to be negative for red cell alloantibodies. Her current full blood examination includes the following: haemoglobin 82 g/L [120-155] mean cell volume 99 fL [80-97] reticulocyte count 162 x 109/L [8-104] Her blood film is shown below. The most likely cause of her anaemia is:

A patient with aortic regurgitation has the following haemodynamic measurements: cardiac output (CO) 7.5 L/minute heart rate (HR) 75/minute left ventricular end-diastolic volume (LVEDV) 200 mL left ventricular end-systolic volume (LVESV) 50 mL The regurgitant fraction is defined as the ratio of the regurgitant volume to the total volume flowing through the valve with each beat. The regurgitant fraction in this patient is:

Which of the following best describes the antiviral effect of zanamivir on the influenza virus?

A 60-year-old man with a five-year history of type 2 (non-insulin-dependent) diabetes mellitus presents for a routine checkup. The most appropriate screening test for the presence of diabetic nephropathy is:

A patient is taking Drug A for a chronic condition. Drug B is added for a period of time and then stopped. The half-life of both drugs is between 6 and 12 hours. The following graph shows the total and free concentrations of Drug A: before Drug B is added, over the time Drug B is added, and after Drug B is ceased. The most likely mechanism for the interaction is:

Which one of the following is the most important consideration in optimising treatment outcome from combination chemotherapy?

A 54-year-old man presents with neck pain. Examination reveals a limited range of movement of the neck. Which feature on the X-ray shown above best explains the limited range of movement?

Which of the following is most characteristic of healthy ageing muscle?

Which one of the following best explains the mechanism of trigeminal neuralgia?

Consider the portion of an exon shown below. The DNA sequence is presented as nucleotide triplets, reflecting the reading frame of the gene. A numbering system for the nucleotides is shown below the sequence. Which one of the following mutations is least likely to have an effect on the amino acid sequence of the protein encoded by this gene?

Which of the following is the strongest predictor of mortality in patients on haemodialysis for chronic renal failure?

A 22-year-old male presents with his fourth episode of pancreatitis. A computed tomography (CT) scan of the pancreas is shown above. He has two first degree relatives with chronic pancreatitis. There is no other significant family history. The most likely explanation for his episodes is:

A 20-year-old male student is referred by his general practitioner with difficulty concentrating and a disturbed sleep pattern. He finds it difficult to stay awake during classes, often needing catnaps during the day, and has to get up at 5 a.m. to complete his course work. His body mass index (BMI) is 31 kg/m2 [18-26]. A polysomnographic sleep study result is shown below. What is the most likely diagnosis?

Which one of the following cells of the immune system is most reliant on its release of mediators into the extracellular fluid surrounding the organism in order to carry out its role in eradication of foreign organisms?

Which of the following findings is most specific for a diagnosis of pernicious anaemia?

A 36-year-old woman has a very strong family history of premature coronary disease. Physical examination is normal. Fasting lipid profile reveals: total cholesterol 9.5 mmol/L [2.5-5.2] high-density lipoprotein (HDL) cholesterol 1.5 mmol/L [0.9-1.8] triglycerides 2.00 mmol/L [0.10-1.85] Which abnormality is most likely to be present?

The most common mechanism for malignant ascites is:

Drugs A and B have the following properties in healthy individuals: In such healthy individuals, haemodialysis shortens the half-life of drug A much more than it shortens the half-life of drug B. This difference is best explained by which of the following characteristics of drug B?

In a patient with unilateral facial weakness, which one of the following findings on physical examination most strongly suggests a peripheral cause for the facial weakness?

Which of the following best describes the changes in regional deposition of adipose tissue that occur with ageing? Key to symbols: ↓ = decrease ↑ = increase

A 40-year-old woman with a 20-year history of systemic lupus erythamatosus (SLE) presents with severe anterior chest pain, dyspnoea and nausea. Her SLE has manifested previously as arthritis, rash, mucosal ulceration and focal proliferative glomerulonephritis. She has had two miscarriages and delivered two normal children. Treatment has included hydroxychloroquine, prednis(ol)one in doses of 7.5 mg to 100 mg daily, intermittent cyclophosphamide and azathioprine. At presentation she is taking prednis(ol)one 7.5 mg daily and hydroxychloroquine. Physical examination reveals obesity, pulse rate of 105/minute, blood pressure of 105/75 mmHg, normal heart sounds, and clear lung fields. The jugular venous pulse and pressure are obscured by fat. Laboratory results show: haemoglobin 124 g/L [115-165] white cell count 3.4 x109/L [3.5-11.0] lymphocytes 0.9 x109/L [1.5 – 4.0] erythrocyte sedimentation rate (ESR) 35 mm/hr [0-20] ECG shows ST-segment elevation in the anterior chest leads and sinus tachycardia. During the assessment, the patient develops ventricular fibrillation and dies. Which of the following is the most likely cause of her death?

A 35-year-old man presents with several weeks of generalised unwellness, epigastric pain, vomiting and headaches. He has no past medical history of note. He has a smoking history of 15 pack years and uses daily cannabis. He has been holidaying at the beach for the summer and is tanned. He is mildly dehydrated. The rest of the physical examination is unremarkable. Blood tests show: sodium 139 mmol/L [138-145] potassium 5.4 mmol/L [3.5-5.2] corrected calcium 3.10 mmol/L [2.15-2.57] phosphate 1.50 mmol/L [0.87-1.45] urea 10.4 mmol/L [3.5-8.0] creatinine 0.32 mmol/L [0.05-0.12] parathyroid hormone 0.6 pmol/L [1.6-6.2] His chest X-ray is shown below. What mechanism best explains the hypercalcaemia?

Which of the following is most likely to cause predominantly zone 1 (periportal) rather than zone 3 (centrilobular) liver pathology?

During normal haemostasis, von Willebrand factor (vWF) plays a role in platelet adhesion/aggregation. During this process, which of the following is the primary binding site of vWF to platelets?

Which of the following is the most effective therapy for hyperphosphataemia associated with chronic renal failure?

Many familial disorders are due to mutations in genes for transcription factors. Which of the following statements is the best description of the role of a transcription factor? It:

Which of the following most accurately reflects the mechanism of complement consumption induced by complement component 3 (C3) nephritic factors?

Which of the following is the most important reason for not recommending gentamicin for the treatment of coliform central nervous system (CNS) infections?

An asymptomatic 45-year-old male with no risk factors for coronary artery disease (CAD) is sent by his general practitioner to have an exercise ECG. At peak exercise, the heart rate is 160/minute and there is 0.7 mm of horizontal ST depression. The relationship between pre-test and post-test probability of significant coronary artery disease is shown below according to the ECG changes occurring at maximal exercise. What is the probability that this man has significant CAD?

The most common identifiable cause of epilepsy in the elderly is:

A 40-year-old woman treated for Hodgkin’s disease in her early twenties with mantle radiotherapy is at highest risk of which of the following cancers?

A 47-year-old male presents with haemoptysis on a background of a 47 pack year smoking history. A chest X-ray shows an irregular mass lesion in the right lower lobe, and sputum examination reveals large undifferentiated malignant cells. Which of the following is the most sensitive method of determining if the mediastinal lymph nodes are involved with the disease?

The deterioration in glycaemic control over time seen in patients with type 2 (non-insulin-dependent) diabetes mellitus is primarily due to:

In a study of polymorphisms in the gene encoding the β2-adrenergic receptor, 20% of people were heterozygous for a polymorphism at codon 16 and 22% were heterozygous for a polymorphism at codon 27. 18% of the population were heterozygous at both loci. Which one of the following statements is the best explanation for this observation?

A test is used to screen for a target disorder. The best definition of the specificity of the test is “the proportion of individuals:

Of the following conditions, which has the greatest contraindication to therapy with bupropion (Zyban) for smoking cessation?

With advancing age, there is an increase in collagen content in the wall of the aorta associated with fragmentation of elastin fibres. These structural changes are thought to have an important influence on the aortic pulse, systemic pressure, and ventricular performance. The table below provides a selection of possible changes in aortic function. Which changes are most commonly seen with advancing age? Key: Change (with advancing age): ⇔ = no change; ⇑ = increase; ⇓ = decrease.

In therapy with immunosuppressive drugs (the relevant drugs are shown in brackets), knowledge of which of the following genotypes is most likely to be useful in preventing serious adverse drug events?

Carbimazole acts predominantly by inhibiting which of the following mechanisms?

A 57-year-old male presents with progressive breathlessness on exercise over five years. His lung function tests are shown above. What is the most likely diagnosis from the lung function tests?

Liberation of dietary cobalamin from R-proteins would be most likely to be adversely affected by:

The most common cause of chronic incontinence in the elderly is:

Intravenous infusion of which of the following blood components is most likely to be associated with a septic transfusion reaction?

In the treatment of hepatitis C infection with interferon and ribavirin, which one of the following is the best predictor of sustained virological response?

Efalizumab is a humanized monoclonal antibody active against an adhesion molecule (CD11a) and is used in the treatment of psoriasis. Which of the following is the best explanation for the therapeutic effect of efalizumab?

Which one of the following patterns of electrolyte changes is most consistent with tumour lysis? Key to symbols: ↓ = decrease ↑ = increase

A 24-year-old is noted to have persistent microscopic haematuria following an insurance examination. Which one of the following factors provides the strongest indication for a renal biopsy?

Which one of the following statements is the best description of the molecular basis of a chimaeric protein (eg Bcr-Abl)?

A 57-year-old man with a long history of poorly controlled hypertension and smoking presents with sudden onset of right-sided weakness. On examination, his speech is slurred but content and comprehension are normal. There is a right facial weakness, with the right side of the soft palate elevating poorly. He has a right hemiparesis, power grade 2-3/5, in a pyramidal distribution with normal sensation to all modalities. Right-sided reflexes are enhanced with an extensor right plantar response. The most likely cause of this stroke syndrome is left:

Which one of the following conditions is most likely to develop in a patient with panic disorder?

Which of the following dietary factors most increases the risk of gout?

The most common cause of diarrhoea in an adult traveller to a developing country is:

Bosentan is one of a number of new pharmacological therapies for pulmonary hypertension. Which of the following best describes the predominant mechanism of action of bosentan?