A patient presents with an inability to abduct his right shoulder.
Which nerve supplies the deltoid muscle?
Correct Answer D:
Shoulder abduction - deltoid muscle - axillary nerve (C5,C6).
Upper limb anatomy:
The information below contains selected facts which commonly appear in examinations:
Deltoid muscle:
In a normal distribution what percentage of values lie within 3 standard deviations of the mean?
Normal distribution:
The normal distribution is also known as the Gaussian distribution or 'bell-shaped' distribution. It describes the spread of many biological and clinical measurements.
Properties of the Normal distribution:
Standard deviation:
A 15-year-old girl presents with abdominal pain. She is normally fit and well and currently takes a combined oral contraceptive pill. The patient is accompanied by her mother, who is known to have hereditary spherocytosis. The pain is located in the upper abdomen and is episodic in nature, but has become severe today. There has been no change to her bowel habit and no nausea or vomiting.
What is the most likely diagnosis?
Correct Answer E:
This patient has hereditary spherocytosis resulting in chronic haemolysis and gallstone formation. An important differential in a poorly patient with hereditary spherocytosis would be splenic rupture.
Hereditary spherocytosis:
Basics:
Presentation:
Diagnosis:
Management:
A patient receives vincristine to help treat non-Hodgkin's lymphoma.
What stage in the cell cycle does vincristine act?
Correct Answer C:
Vincristine inhibits formation of microtubules and arrests mitosis.
Cell cycle:
A new screening test is developed for colorectal cancer. It is a blood test which detects a protein; the higher the level of the protein, the more likely a patient is to have colorectal cancer. If the cut-off for a positive test is increased, which one of the following will also be increased?
Correct Answer B:
Increasing the cut-off of a positive test result will decrease the number of false positives and hence increase the specificity.
Screening test statistics:
It would be unusual for a medical exam not to feature a question based around screening test statistics. The available data should be used to construct a contingency table as below:
TP = true positive; FP = false positive; TN = true negative; FN = false negative
The table below lists the main statistical terms used in relation to screening tests:
Positive and negative predictive values are prevalence dependent. Likelihood ratios are not prevalence dependent.
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