2) Flashcards
Which of the following malignancies does NOT have a strong association with HIV infection?
A. Acute lymphoblastic leukaemia B. Burkitt's lymphoma C. Cervical carcinoma D. Diffuse large B cell lymphoma E. Kaposi's sarcoma
The correct answer is acute lymphoblastic lymphoma as all of the other options have a strong association with HIV infection. This is because they are related to viral infection and the immunosuppression associated with HIV infection allows the viral infections to progress and potentially cause malignancy. An association of acute lymphoblastic lymphoma with HIV is much rarer.
A 25 year old woman is found to have an ovarian mass. It is removed surgically and when opened found to contain hair and sebum. On microscopic examination squamous epithelium with hair follicles, cartilage and neural tissue are identified.
Which of the following statements about this type of neoplasm is true?
Infection with human papillomavirus (HPV) predisposes to this type of tumour.
Metastases are unlikely to be present.
Patients with these tumours often present with irregular menstrual bleeding.
Primitive mature tissue resembling that from an embryo can usually be seen.
These tumours are associated with BRCA1 mutations.
Metastases are unlikely to be present.
CORRECT – Colloquially known as a dermoid cyst, the patient is suffering from a mature teratoma which is a germ cell tumour commonly composed of multiple cell types derived from one or more of the 3 germ layers. This is because the mass consists of mature tissues such as hair and sebum. Mature teratomas are normally benign and so do not metastasise.
A 49 year old man has weakness when trying to extend his left great toe and numbness over the dorsum of his left foot. He also reports increased pain when sitting. The GP believes that the man may have a herniation of an intervertebral disc resulting in impingement of a spinal nerve root.
Which spinal nerve is most likely to have been affected by this herniation?
L2 Spinal Nerve L3 Spinal Nerve L5 Spinal Nerve S1 Spinal Nerve S2 Spinal Nerve
CORRECT The L5 dermatome supplies the anterior leg and the medial three toes. The associated myotome allows for great toe extension.
spinal_nerve spinal_nerve
A 34 year old woman presents to her GP with symptoms of dysuria and frequency suggesting that she has a urinary tract infection. The UHL antimicrobial website suggests that woman should be treated with Trimethoprim.
What is the mechanism of action for this drug?
Inhibition of folic acid synthesis
Inhibits protein synthesis
Inhibits pathogen pili binding to host tissue
Interferes with bacterial cell wall synthesis
Destroys bacterial cell walls
Inhibition of folic acid synthesis
CORRECT – Urinary Tract Infections (UTIs) are common. Trimethoprim is commonly used alone for the treatment of UTIs. Trimethoprim inhibits folic acid synthesis in bacteria and thereby affects nucleic acid synthesis. Enzymes requiring folate-derived cofactors are essential for the synthesis of purines, pyrimidines and other compounds necessary of cellular growth and replication. Therefore, in the absence of folate, cells cannot grow or replicate.
What proportion of plasma thyroid hormone (T3 and T4) is “free” in plasma (i.e. not bound to proteins such as Thyroxine-binding globulin or albumin)?
~1% ~10% ~50% ~90% ~99%
around 1%
CORRECT. The vast majority of thyroid hormone is bound to binding protein in plasma. It is only the free form however that is biologically active.
A group of researchers working on behalf of Public Health England want to investigate the relationship between the incidence strokes and the frequency of headaches that the patient had experienced. As strokes are often very traumatic events for patients, the researchers want to do their best to eliminate recall bias.
Which of the following study types is immune to recall bias?
Historical Cohort Study Prospective Cohort Study Ecological Study Case Control Study Cross-Sectional Survey
ecological study
CORRECT – Recall bias occurs when one group of individuals are more likely to remember certain events about their history compared to another group. For example, in the current case, individuals that have suffered a stroke, may associate the stroke with headaches and so would be more likely to report a high frequency of headaches in their childhood. Individuals that have not experienced a stroke may not make the same association and so may not report as many childhood headaches. This can lead to a misclassification of participants, with a much lower proportion of non-stroke victims being classified as reporting a high number of childhood headaches (differential misclassification). This can make the results less reliable as a result of the bias. Ecological studies suffer from the lowest amount of recall bias.
A 42 year old woman has a liver biopsy. The histology report describes the presence of Mallory’s hyaline within the hepatocytes.
With which condition is this finding classically associated?
A. Alcoholic liver disease B. Alpha-1 antitrypsin deficiency C. Diabetes mellitus D. Hereditary haemochromatosis E. Hypercholesterolaemia
alcoholic liver disease
Mallory’s hyaline is damaged keratin filaments seen in hepatocytes in alcoholic liver disease. Abnormal cellular accumulations can be seen in all the other conditions but in none of them is Mallory’s hyaline classically seen. Incorrectly folded alpha-1 antitrypsin protein is seen in hepatocytes in alpha-1 antitrypsin deficiency. Fat droplets can be seen in hepatocytes in diabetes mellitus. Iron is seen in many cells in hereditary haemochromatosis. Cholesterol can be seen in cells such as dermal histiocytes in hypercholesterolaemia.
Following a myocardial infarction, a 59 year old man is referred to the angioplasty clinic to remove a clot from his left anterior descending coronary artery. On admittance a 12-lead ECG is recorded.
Which ECG leads would give the best view to determine occlusion of this artery?
AVL, AVF and AVR
V1 to V4
V1, V2, II III and AVF
V5 and V6
CORRECT - Leads V1 to V4 provide a view of the anteroseptal aspect of the heart. This view will provide highlight any areas of the heart that have undergone an infarction as a response to an occlusion of the left anterior descending coronary artery.
coronary_arteries
A 29 year old man takes part in a haemodynamic monitoring study where blood flow is measured using an echo-doppler probe. The flow of blood in the man’s thoracic aorta was found to be double that of the flow in his right common iliac artery.
What parameter determines this difference in blood flow?
Blood flow in the iliac arteries is impeded by the presence of valves
Blood pressure is lower further from the heart.
Differences in blood vessel radius.
Differences in blood viscosity.
Turbulent blood flow due to atherosclerosis.
Differences in blood vessel radius.
CORRECT – Flow (F) of blood in a vessel is related to velocity (V), the distance blood moves in a given time, and the cross-sectional area of the vessel, shown by the formula F = V x A, where A = πr2. Resistance to flow is primarily due to the diameter of the vessel, and as such changes in the radius of a vessel have a 4th power relationship to flow and resistance.
A 24 year old man with a severe infection of a wound on his leg develops sepsis.
Which of the following is a red flag symptom of this condition in a healthy adult?
National Early Warning Score of 3 of more
National Early Warning Score of 3 of more in the context of abdominal pain
National Early Warning Score of 3 of more in the context of a device related infection
Respiratory rate of 20 breaths per minute
Systolic blood pressure of less than or equal to 90 mmHg
CORRECT – A systolic blood pressure of less than or equal to 90mmHg is a Red Flag symptom of sepsis.
red flags of sepsis
1) Only responsive only to voice/ pain- unresponsive
2) acute confused state
3) systolic bp <90mmHg
4) heart rate above 130
5) resp rate above 25
6) needs O2 to keep sO2 above 92%
7) non blanching rash
8) not passed urine in 18h
9) lactate >2 mol/l
10) recent chemotherapy
Researchers working on behalf of NHS England are designing an experiment to investigate the relationship between the incidence of peanut allergy in neonates and breastfeeding. They wish to reduce selection bias in their study by as much as possible.
How is this type of bias defined?
The individuals in one group of the study have a much greater recall of events than the other
When comparing groups, the association or effect between an exposure and outcome is distorted by the presence of another variable
Selection bias occurs when the study sample does not reflect the entire population or when the groups in a study are not comparable
The observer has preconceived notions about the study and so does not accurately place participants into the correct group
Selection bias occurs when the study sample does not reflect the entire population or when the groups in a study are not comparable
CORRECT – This is a definition of selection bias.
A disproportionately higher number of controls die during follow up compared to non-cases
