Which one of the following causes of primary immunodeficiency is due to a defect in B-cell function?
Correct Answer C:
Primary immunodeficiency:
Primary immunodeficiency disorders may be classified according to which component of the immune system they affect: 1- Neutrophil disorders:
2- B-cell disorders:
3- T-cell disorders:
4- Combined B- and T-cell disorders:
Which of the following is most likely to cause hypokalaemia associated with alkalosis?
Correct Answer D:
Hypokalaemia and acid-base balance:
Potassium and hydrogen can be thought of as competitors. Hyperkalaemia tends to be associated with acidosis because as potassium levels rise fewer hydrogen ions can enter the cells.
Hypokalaemia with alkalosis:
Hypokalaemia with acidosis:
Which one of the following statements is true regarding cytoplasmic anti-neutrophil cytoplasmic antibodies (cANCA)?
Correct Answer B:
cANCA = Wegener's; pANCA = Churg-Strauss + others
ANCA:
There are two main types of anti-neutrophil cytoplasmic antibodies (ANCA) - cytoplasmic (cANCA) and perinuclear (pANCA).
For the exam, remember:
cANCA - Wegener's granulomatosis
pANCA - Churg-Strauss syndrome + others (see below)
cANCA:
pANCA:
Other causes of positive ANCA (usually pANCA):
Which one of the following is most commonly secreted by T-helper cells subset 2 (Th2 cells) ?
T-Helper cells:
There are two major subsets of T-Helper cells:
Th1:
Th2:
What is the correct formula to calculate the negative predictive value of a screening test?
TP = true positive; FP = false positive; TN = true negative; FN = false negative
Correct Answer A: 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:
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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