A 67-year-old man presents with shortness-of-breath. He has a past history of aortic stenosis but is otherwise well. On examination he has a systolic murmur and a clear chest. Routine bloods are as follows:
Which one of the following investigations is most likely to explain his anaemia?
Correct Answer A: This patient most likely has angiodysplasia which has a known association with aortic stenosis.
Angiodysplasia: Angiodysplasia is a vascular deformity of the gastrointestinal tract which predisposes to bleeding and iron deficiency anaemia. There is thought to be an association with aortic stenosis, although this is debated.
Angiodysplasia is generally seen in elderly patients.
Diagnosis:
Management:
Which one of the following statements best describes a type I statistical error?
Correct Answer A:
Significance tests: A null hypothesis (H0) states that two treatments are equally effective (and is hence negatively phrased). A significance test uses the sample data to assess how likely the null hypothesis is to be correct.
For example:
The alternative hypothesis (H1) is the opposite of the null hypothesis, i.e. There is a difference between the two treatments.
The p value is the probability of obtaining a result by chance at least as extreme as the one that was actually observed, assuming that the null hypothesis is true. It is therefore equal to the chance of making a type I error.
Two types of errors may occur when testing the null hypothesis:
The power of a study is the probability of (correctly) rejecting the null hypothesis when it is false, i.e. the probability of detecting a statistically significant difference:
Which one of the following statements regarding the standard error of the mean is correct?
Correct Answer E:
Standard error of the mean:
The standard error of the mean (SEM) is a measure of the spread expected for the mean of the observations - i.e. how 'accurate' the calculated sample mean is from the true population mean Key point:
Therefore the SEM gets smaller as the sample size (n) increases A confidence interval for the mean can be calculated in a similar way to that for a single observation, i.e. The 95% confidence interval:
Which one of the following hormones is under continuous inhibition?
Correct Answer B: Prolactin - under continuous inhibition.
Prolactin is unique amongst the pituitary hormones in being tonically inhibited by the hypothalamus.
Prolactin and galactorrhoea:
Prolactin is secreted by the anterior pituitary gland with release being controlled by a wide variety of physiological factors. Dopamine acts as the primary prolactin releasing inhibitory factor and hence dopamine agonists such as bromocriptine may be used to control galactorrhoea. It is important to differentiate the causes of galactorrhoea (due to the actions of prolactin on breast tissue) from those of gynaecomastia.
Features of excess prolactin:
Causes of raised prolactin:
Drug causes of raised prolactin:
What is the main constituent of pulmonary surfactant?
Correct Answer E: Pulmonary surfactant - main constituent is dipalmitoyl phosphatidylcholine (DPPC).
Pulmonary surfactant:
Surfactant is a mixture of phospholipids, carbohydrates and proteins released by type 2 pneumocytes. The main functioning component is dipalmitoyl phosphatidylcholine (DPPC) which reduces alveolar surface tension.
Basics:
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