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Question 1
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A 42-year-old man with a 6 month history of progressive weakness of both lower limbs, complains of lethargy and of difficulties climbing stairs. He also claims he's experienced muscle loss in his lower limbs. History reveals type 2 diabetes mellitus and heavy alcohol use for the last 4 years. Clinical examination reveals marked loss of fine touch and proprioception. The distribution is in a stocking manner and bilateral. However, no evidence of ataxia is present. What is the most probable diagnosis?
Your Answer: Dry beriberi
Explanation:Hypovitaminosis B1, consistent with dry beriberi is crucially a treatable condition, although sometimes with incomplete recovery, but it is probably under-recognized yet increasingly common given increasing levels of alcohol abuse in the western world. Dry beriberi or ‘acute nutritional polyneuropathy’ is considered to be rare in the western world. Rapid deterioration can occur, typically with weakness, paraesthesia and neuropathic pain. Striking motor nerve involvement can occur, mimicking Guillain-Barré syndrome (GBS). In the context of increasing alcohol abuse in the western world, it is possible that alcoholic neuropathy associated with abrupt deterioration due to concomitant nutritional hypovitaminosis B1 may be seen increasingly often.
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This question is part of the following fields:
- Clinical Sciences
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Question 2
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A 54-year-old man is found collapsed in the street and is brought to the A&E. The results from the blood tests reveal Calcium = 1.62mmol/l and Albumin = 33g/l. The man is known to have a history of alcoholic liver disease. Which of the following is the best management regarding his calcium levels?
Your Answer: 10ml of 10% calcium gluconate over 10 minutes
Explanation:Acute, symptomatic hypocalcaemia is treated with 10ml of 10% calcium gluconate over 10 minutes.
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This question is part of the following fields:
- Clinical Sciences
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Question 3
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A 45-year-old woman with a history of hypothyroidism, presents with ptosis and muscle weakness. She's noticed that her muscle weakness becomes worse towards the end of the day. Clinical examination reveals fatigable ptosis and proximal limb weakness. Myasthenia gravis is suspected. Which receptor is implicated in the pathophysiology of this condition?
Your Answer: Nicotinic acetylcholine receptors
Explanation:Myasthenia gravis (MG) is an organ-specific autoimmune disease caused by an antibody-mediated assault on the muscle nicotinic acetylcholine receptor (AChR) at the neuromuscular junction. Binding of antibodies to the AChR leads to loss of functional AChRs and impairs the neuromuscular signal transmission, resulting in muscular weakness.
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This question is part of the following fields:
- Clinical Sciences
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Question 4
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A 23-year-old male patient with a downward dislocation of the lens in his right eye is experiencing visual problems. The ophthalmologist notes a constellation of symptoms resembling those of Marfan Syndrome. The patient's history reveals learning disabilities and a diagnosis of homocystinuria is suspected. What is the pathophysiology of homocystinuria?
Your Answer: Deficiency of cystathionine beta synthase
Explanation:Inherited metabolic disorders are often characterized by the lack of an essential enzyme and are currently treated by dietary restriction and other strategies to replace the substrates or products of the missing enzyme. Patients with homocystinuria lack the enzyme cystathionine β-synthase (CBS), and many of these individuals do not respond to current treatment protocols.
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This question is part of the following fields:
- Clinical Sciences
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Question 5
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170 patients are enrolled in a study to assess the addition of a new antiplatelet drug to aspirin for those who've had a stroke. Out of 170 patients, 120 received the aspirin in addition to the new drug with the remaining 50 patients receiving just aspirin. After 5 years, 18 out of the 120 patients receiving the new drug in addition to aspirin and 10 out of the 50 patients receiving just aspirin, had had a stroke. What is the number needed to treat?
Your Answer: 20
Explanation:The number needed to treat (NNT) is valuable information in treatment decisions. NNT is the inverse of the absolute risk reduction (1/ARR) between two treatment options. Control event rate = 10 / 50 = 0.2
Experimental event rate = 18 / 120 = 0.15Absolute risk reduction = 0.2 – 0.15 = 0.05
Number needed to treat = 1 / 0.05 = 20 -
This question is part of the following fields:
- Clinical Sciences
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Question 6
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Supplementation of which one of the following might help a patient diagnosed with homocystinuria?
Your Answer: Pyridoxine
Explanation:In general, the aim is to keep the homocysteine (Hcy) concentration as close to normal as possible. In patients who are fully-responsive to pyridoxine, standard doses can lead to tHcy levels below 50 μmol/L (and sometimes within the normal range). Some patients who are partially-responsive to pyridoxine may be able to achieve a tHcy level below 50 μmol/L if they are also on a low-Met diet; for others it is not a realistic goal.
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This question is part of the following fields:
- Clinical Sciences
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Question 7
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The family of a 10-year-old boy was advised to take the boy to see an oncologist, for suspected lymphoma. The boy had lymphadenopathy on presentation. His mother says that he's had a fever, night sweats and has experienced weight loss. The boy underwent a lymph node biopsy at the oncologist which suggests Burkitt's lymphoma. Which oncogene are you expecting to see after molecular testing?
Your Answer: c-MYC
Explanation:Burkitt lymphoma is a germinal centre B-cell-derived cancer that was instrumental in the identification of MYC as an important human oncogene more than three decades ago. Recently, new genomics technologies have uncovered several additional oncogenic mechanisms that cooperate with MYC to create this highly aggressive cancer.
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This question is part of the following fields:
- Clinical Sciences
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Question 8
Correct
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Which is the best source of vitamin D per average serving for a woman with suspected Osteomalacia?
Your Answer: Cod liver oil
Explanation:Serum vitamin D levels are influenced by sun exposure and diet. Cod liver oil is an important dietary vitamin D source in high-latitude countries like Norway where there is no sun-induced vitamin D production during the winter. 14 Norwegian Health Authorities have recommended 5 ml of cod liver oil daily (400 IU of vitamin D) for more than 60 years to prevent diseases like rickets, formerly more prevalent in areas with little access to vitamin D-rich fatty fish.
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This question is part of the following fields:
- Clinical Sciences
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Question 9
Correct
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A 60-year-old male presents with dyspnoea and an urgent chest X-ray is scheduled. Sputum cultures reveal pneumonia and he receives treatment with erythromycin. What is the mechanism of action of this drug?
Your Answer: Inhibit 50S subunit of ribosomes
Explanation:Erythromycin is a bacteriostatic antibiotic. This means it stops the further growth of bacteria rather than directly destroying it. This is achieved by inhibiting protein synthesis. Erythromycin binds to the 23S ribosomal RNA molecule in the 50S subunit of the bacterial ribosome. This causes a blockage in the exiting of the peptide chain that is growing. Given that humans have 40S and 60S subunits, and do not have 50S subunits, erythromycin does not affect protein synthesis in human tissues.
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This question is part of the following fields:
- Clinical Sciences
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Question 10
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A 34-year-old man presents with haemoptysis and weight loss. History reveals he suffers from night sweats and upon auscultation you notice reduced breath sounds over the apex of his right lung and significant nail clubbing. You refer him to a pneumologist who administers the following antibiotics: rifampicin, ethambutol, pyrazinamide and isoniazid. What is the mechanism of action of the first drug?
Your Answer: Inhibit RNA synthesis
Explanation:Rifampicin specifically inhibits bacterial RNA polymerase, the enzyme responsible for DNA transcription, by forming a stable drug-enzyme complex with a binding constant of 10(-9) M at 37 C.
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This question is part of the following fields:
- Clinical Sciences
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Question 11
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A literature review of a number of studies was conducted to assess the potential efficacy of a new drug, which may reduce the chance of patients with chronic kidney disease (CKD) developing gout. In one study 120 out of 1,200 patients receiving the new drug developed gout. The total number of the patients were 2,000 and the remaining 800 individuals received a placebo. From the patients that had received the placebo, 200 developed gout. What is the absolute risk reduction of developing gout?
Your Answer: 15%
Explanation:Absolute risk reduction (ARR) – also called risk difference (RD) – is the most useful way of presenting research results to help your decision-making. Absolute risk reduction = (Control event rate) – (Experimental event rate) = 0.15 = 15%
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This question is part of the following fields:
- Clinical Sciences
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Question 12
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A 61-year-old female presents to the A&E with malaise and muscle twitching. Her blood pressure is 114/78 mmHg and her pulse is 84/min. Blood exam reveals Calcium = 1.94 mmol/l and Albumin = 38 g/l. Which of the following tests is most useful in establishing her diagnosis?
Your Answer: Parathyroid hormone
Explanation:Hypocalcaemia occurs in patients with impaired function of the parathyroid glands. This is most common after thyroid or parathyroid surgery, but it can be idiopathic—mostly in young adults and less often as part of a genetic syndrome, such as autoimmune polyglandular syndrome type 1. Usually, the first and most useful test to perform in such cases is the measurement of the parathyroid hormone.
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This question is part of the following fields:
- Clinical Sciences
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Question 13
Correct
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Which is the most common chromosomal defect in Down's syndrome?
Your Answer: Non-dysjunction
Explanation:Nondisjunction of chromosome 21 is the leading cause of Down syndrome. Two risk factors for maternal nondisjunction of chromosome 21 are increased maternal age and altered recombination.
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This question is part of the following fields:
- Clinical Sciences
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Question 14
Incorrect
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A cohort study is being designed to look at the relationship between smoking and prostate cancer. What is the usual outcome measure in a cohort study?
Your Answer: Absolute risk increase
Correct Answer: Relative risk
Explanation:A cohort study is a particular form of longitudinal study that samples a cohort (a group of people who share a defining characteristic, typically those who experienced a common event in a selected period, such as birth or graduation), performing a cross-section at intervals through time.
The relative risk (RR) or risk ratio is the ratio of the probability of an outcome in an exposed group to the probability of an outcome in an unexposed group. Relative risk is used in the statistical analysis of the data of experimental, cohort and cross-sectional studies, to estimate the strength of the association between treatments or risk factors, and outcomes. -
This question is part of the following fields:
- Clinical Sciences
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Question 15
Correct
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What kind of receptor is the nitric oxide receptor?
Your Answer: Guanylate cyclase receptor
Explanation:Soluble guanylyl cyclase (GC-1) is the primary receptor of nitric oxide (NO) in smooth muscle cells and maintains vascular function by inducing vasorelaxation in nearby blood vessels. GC-1 converts guanosine 5′-triphosphate (GTP) into cyclic guanosine 3′,5′-monophosphate (cGMP), which acts as a second messenger to improve blood flow.
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This question is part of the following fields:
- Clinical Sciences
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Question 16
Incorrect
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A 27-year-old lady presents with severe morning headaches associated with nausea. Head MRI reveals a large compressive tumour arising from the falx cerebri. The tumour is well delineated. What is the most probable diagnosis?
Your Answer: Low-grade glioma
Correct Answer: Meningioma
Explanation:Meningiomas are the most common benign tumours of the brain. Their name is derived from the fact that they arise from the dura mater which together with the pia matter and arachnoid mater form the meninges. The chances that a meningioma is benign are almost 98%. They are non-invasive and well delineated, causing sign and symptoms of brain compression.
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This question is part of the following fields:
- Clinical Sciences
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Question 17
Incorrect
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A 34-year-old male patient is admitted with hemisection of the spinal cord at the level T5, after being stabbed in the back. Which sign would you expect to see by assessing the patient's sensory function and muscle strength?
Your Answer: Contralateral loss of temperature, ipsilateral loss of fine touch and vibration, contralateral spastic paresis
Correct Answer: Contralateral loss of temperature, ipsilateral loss of fine touch and vibration, ipsilateral spastic paresis
Explanation:Depending on the level of SCI, patients experience paraplegia or tetraplegia. Paraplegia is defined as the impairment of sensory or motor function in lower extremities. Patients with incomplete paraplegia generally have a good prognosis in regaining locomotor ability (,76% of patients) within a year. Complete paraplegic patients, however, experience limited recovery of lower limb function if their NLI is above T9. The spinothalamic tract is the one responsible for sensory information such as pain or temperature. However, it decussates at the same level the nerve root enters the spinal cord, meaning that the sensory loss will be contralateral. However, the dorsal column carries sensory fibres for fine touch and vibration and it decussates at the medulla which means that the sensory loss will be ipsilateral. The corticospinal tract is responsible for motor functions and it decussates at the medulla, meaning that the motor function loss will be ipsilateral.
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This question is part of the following fields:
- Clinical Sciences
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Question 18
Incorrect
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A 67-year-old man presents with anaemia and weight loss. Upon endoscopy, a gastric tumour is revealed, later established as an adenocarcinoma. The patient refuses any treatment and claims that his condition is not influencing the quality of his life. Clinical examination has nothing particularly interesting to show and the patient seems to be conscious of his decision, regardless of the likely curative nature of surgery. What is the single most appropriate management?
Your Answer: Arrange an appointment with a psychiatrist
Correct Answer: Respect his wishes and book a follow-up appointment for four weeks
Explanation:The patient seems to be conscious about his decision, which should be respected. According to Mental Capacity Act 2005, a person who makes an unwise decision should not be treated as unable to make a decision.
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This question is part of the following fields:
- Clinical Sciences
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Question 19
Incorrect
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Choose the part of the renal tubule which is impermeable to water:
Your Answer: Thick ascending limb of loop of Henle
Correct Answer: Thin ascending limb of loop of Henle
Explanation:The thick ascending limb actively reabsorbs NaCl but has an extremely low transepithelial osmotic water permeability, even in the presence of vasopressin. This combination of NaCl reabsorption without water reabsorption serves two vital functions: it provides NaCl to increase the osmolality of the medullary interstitium, tubules, vasculature, and collecting ducts; and it dilutes the luminal fluid within the thick ascending limb.
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This question is part of the following fields:
- Clinical Sciences
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Question 20
Correct
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Sensorineural deafness is strongly associated with which one of the following?
Your Answer: Rubella
Explanation:Primary rubella infection during pregnancy, particularly during the first trimester, can affect several organs and cause birth defects that are responsible for congenital rubella syndrome (CRS). The most common defects of CRS are hearing impairment (unilateral or bilateral sensorineural), eye defects (e.g., cataracts, congenital glaucoma, or pigmentary retinopathy), and cardiac defects (e.g., patent ductus arteriosus or peripheral pulmonic stenosis). Congenital hearing loss is the most common sequela, occurring in approximately 60% of cases, especially when infection occurs in the 4th month of pregnancy.
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This question is part of the following fields:
- Clinical Sciences
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Question 21
Correct
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Choose the correct statement regarding the standard error of the mean:
Your Answer: Gets smaller as the sample size increases
Explanation:When statistically comparing data sets, researchers estimate the population of each sample and examine them to see whether they are identical. The standard error of the mean (SEM) – not the standard deviation (SD), which represents the variation in the sample – is used to estimate the population mean. Via this process, researchers conclude that the sample used in their studies appropriately represents the population within the error range specified by the pre-set significance level.
The SEM is smaller than the SD, as the SEM is estimated usually with the SD divided by the square root of the sample size. For this reason, researchers are tempted to use the SEM when describing their samples. It is acceptable to use either the SEM or SD to compare two different groups if the sample sizes of the two groups are equal; however, the sample size must be stated in order to deliver accurate information. For example, when a population has a large amount of variation, the SD of an extracted sample from this population must be large. However, the SEM will be small if the sample size is deliberately increased. -
This question is part of the following fields:
- Clinical Sciences
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Question 22
Correct
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Which one of the following occurs during reverse transcriptase polymerase chain reaction?
Your Answer: RNA is converted to DNA
Explanation:Reverse transcription polymerase chain reaction is a laboratory technique combining reverse transcription of RNA into DNA and amplification of specific DNA targets using polymerase chain reaction. It is primarily used to measure the amount of a specific RNA. The main advantage of PCR is its sensitivity: only one strand of sample DNA is needed to detect a particular DNA sequence. It now has many uses including prenatal diagnosis, detection of mutated oncogenes and diagnosis of infections.
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This question is part of the following fields:
- Clinical Sciences
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Question 23
Correct
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A 19-year-old woman is admitted with diabetic ketoacidosis (DKA). It is her fourth episode in the past two months and she's known to be a type 1 diabetes mellitus patient. The doctors suspects she's non-compliant with her treatment to keep her weight down. She often self-discharges after 24 hours. What is the single most appropriate management?
Your Answer: Have a chat after the ward round about why she thinks her control is so bad
Explanation:In many Western countries and health plans in the United States, patients have a primary care physician who acts as a formal gatekeeper for medical specialist care and thereby determines together with the patient whether or not a patient requires medical specialist care. Ideally in such systems, patients are treated in primary care if possible, and referred to medical specialist care if necessary. For the gatekeeper system to be effective, it is vital that adequate decisions are made about when and who to refer. But it is also important that referred patients comply with the referral by consulting a medical specialist. In this case, the GP should discuss with the patient the reasons why she cannot follow the treatment plan. In other words, the GP should detect why the patient is being non-compliant.
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This question is part of the following fields:
- Clinical Sciences
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Question 24
Correct
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Choose the correct formula to calculate the negative predictive value of a screening test:
Your Answer: TN / (TN + FN)
Explanation:NPV = TN / FN+TN
= TN (true negative) / FN+TN (false negative + true negative)
= Probability (patient not having disease when test is negative)
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This question is part of the following fields:
- Clinical Sciences
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Question 25
Correct
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A 24-year-old man was hit on the lateral aspect of his head by a high velocity cricket ball and lost consciousness immediately. Paramedics found him to have a Glasgow coma score of 15 but take him to the A&E for further investigation. His Glasgow coma score on examination in the A&E is 13 (M5, V4, E4) and he has anterograde and retrograde amnesia to recent events. The doctors arrange an urgent CT scan. Which clinical sign would be most concerning if present?
Your Answer: Bradycardia
Explanation:Intracranial pressure (ICP) is a complex brain modality that determines cerebral perfusion pressure (CPP), which is the difference between arterial blood pressure (ABP), and ICP. Raised ICP reduces CPP and blood delivery to the brain. This jeopardizes cerebral function and organismal survival in many species. A massive rise in ICP is also known to produce an increase in ABP, bradycardia and respiratory irregularities termed Cushing response. This mechanism is generally considered to be an agonal and terminal event occurring in extreme condition of brainstem ischaemia leading to a sympatho-adrenal response.
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This question is part of the following fields:
- Clinical Sciences
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Question 26
Correct
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Empagliflozin was found to reduce the risk of cardiovascular deaths, non-fatal myocardial infarction and non-fatal stroke when added to standard treatment plans in patients with type 2 diabetes mellitus. This information was shared in 2015 by The New England Journal of Medicine and the results were expressed per 1000 patient years. In fact, empagliflozin had an event rate of 37.3/1000 patient years and placebo an event rate of 43.9/1000 patient years. How many patients who are at high cardiovascular risk need to be treated with empagliflozin to prevent a cardiovascular death, a non-fatal myocardial infarction or a non-fatal stroke?
Your Answer: 150
Explanation:The number needed to treat (NNT) is an absolute effect measure that has been used to assess beneficial and harmful effects of medical interventions. In this case the NNT can be calculated as follows: NNT = 1/ Absolute risk reduction (ARR). ARR=(Control event rate expressed per 1000 patient years) – (Experimental event rate expressed per 1000 patient years) = 43.9-37.3 = 6.6/1000 patient years
NNT=(Patient years)/ARR = 1000/ 6.6 = 151.5. The closest to 151.5 is 150, thus it is the correct answer.
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This question is part of the following fields:
- Clinical Sciences
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Question 27
Incorrect
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Which of the following is not a tumour suppressor gene?
Your Answer: APC
Correct Answer: myc
Explanation:Myc is a family of regulator genes and proto-oncogenes that code for transcription factors.
A tumor suppressor gene, or antioncogene, is a gene that protects a cell from one step on the path to cancer. When this gene mutates to cause a loss or reduction in its function, the cell can progress to cancer, usually in combination with other genetic changes. Tumor suppressor genes can be grouped into categories including caretaker genes, gatekeeper genes, and landscaper genes; the classification schemes are continually evolving.
Examples include:
Gene Associated cancers
p53 Common to many cancers, Li-Fraumeni syndrome
APC Colorectal cancer
BRCA1 Breast and ovarian cancer
BRCA2 Breast and ovarian cancer
NF1 Neurofibromatosis
Rb Retinoblastoma
WT1 Wilm’s tumour -
This question is part of the following fields:
- Clinical Sciences
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Question 28
Correct
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Question 29
Correct
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What is the correct formula to calculate the positive predictive value? (TP = true positive; FP = false positive; TN = true negative; FN = false negative)
Your Answer: TP / (TP + FP)
Explanation:Positive predictive value is the probability that subjects with a positive screening test truly have the disease.
Positive predictive value = true positive / ( true positive + false positive)
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This question is part of the following fields:
- Clinical Sciences
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Question 30
Correct
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A study was developed to assess a new oral antithrombotic drug on the chance of stroke in high-risk patients, compared to warfarin. The total number of patients receiving the new drug were 200 compared to 600 who were receiving warfarin. From the ones receiving the new drug, 10 patients had a stroke within 3 years, compared to 12 patients who were receiving warfarin and had a stroke. What is the relative risk of having a stroke within 3 years for patients receiving the new drug?
Your Answer: 2.5
Explanation:Relative Risk = (Probability of event in exposed group) / (Probability of event in not exposed group)
Experimental event rate, EER = 10 / 200 = 0.05Control event rate, CER = 12 / 600 = 0.02
Therefore the relative risk = EER / CER = 0.05 / 0.02 = 2.5
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This question is part of the following fields:
- Clinical Sciences
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