In the Gell and Coombs classification of hypersensitivity reactions idiopathic thrombocytopenic purpura is an example of a:
Correct Answer B:
Hypersensitivity: The Gell and Coombs classification divides hypersensitivity reactions into 4 types:
Type I - Anaphylactic:
Type II - Cell bound:
Type III - Immune complex:
Type IV - Delayed hypersensitivity:
In recent times a further category has been added:
Type V - Stimulated hypersensitivity:
Which one of the following clinical features would be least consistent with a diagnosis of severe preeclampsia?
Correct Answer C: Severe pre-eclampsia is associated with hyperreflexia and clonus. A low platelet count may indicate the patient is developing HELLP syndrome.
Pre-eclampsia: Pre-eclampsia is a condition seen after 20 weeks gestation characterized by pregnancy-induced hypertension in association with proteinuria (> 0.3g / 24 hours). Oedema used to be third element of the classic triad but is now often not included in the definition as it is not specific.
Pre-eclampsia is important as it predisposes to the following problems:
Risk factors:
Features of severe pre-eclampsia:
Management:
A study measures a patients serum cholesterol before and after a new lipid-lowering therapy has been given.
What type of significance test should be used to analyze the data?
Correct Answer A:
Significance tests: types:
The type of significance test used depends on whether the data is parametric (something which can be measured, usually normally distributed) or non-parametric.
Parametric tests:
Non-parametric tests:
Paired data refers to data obtained from a single group of patients, e.g. Measurement before and after an intervention. Unpaired data comes from two different groups of patients, e.g. Comparing response to different interventions in two groups.
Which one of the following reduces the secretion of renin?
Correct Answer E:
Renin: Renin is secreted by juxtaglomerular cells and hydrolyzes angiotensinogen to produce angiotensin I
Factors stimulating renin secretion:
Factors reducing renin secretion:
Which one of the following is the most common underlying mechanism causing prolongation of the QT segment?
Correct Answer D: Long QT syndrome - usually due to loss-of-function/blockage of K+ channels.
In long QT syndrome QT prolongation is due to overload of myocardial cells with positively charged ions during ventricular repolarization. Around 90-95% of inherited causes are due to defects in potassium channels.
Long QT syndrome:
Long QT syndrome (LQTS) is an inherited condition associated with delayed repolarization of the ventricles. It is important to recognize as it may lead to ventricular tachycardia and can therefore cause collapse/sudden death.
The most common variants of LQTS (LQT1 & LQT2) are caused by defects in the alpha subunit of the slow delayed rectifier potassium channel. A normal corrected QT interval is less than 430 ms in males and 450 ms in females.
Causes of a prolonged QT interval:
Features:
*the usual mechanism by which drugs prolong the QT interval is blockage of potassium channels. See the link for more details
**a non-sedating antihistamine and classic cause of prolonged QT in a patient, especially if also taking P450 enzyme inhibitor, e.g. Patient with a cold takes terfenadine and erythromycin at the same time
***note sotalol may exacerbate long QT syndrome
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