TEALE FENNING

Xerxes I · Posted: Sun Mar 18, 2007 5:01 pm Post subject: Research methodology

This is from RCOG book on EMQs (by Duthie and Hodges) and the reason I am posting it, is that I don't agree with the answer they have given. See what you think:

Options:
A: 125.00
B: 100.00
C: 90.40
D: 90.00
E: 83.00
F: 81.00
G: 80.00
H: 79.00
I: 77.00
J: 16.88
K: 15.46
L: 13.39
M: 5.00
N: 2.50

In a prospective blind study of a possible new method of antenatal fetal screening for a particular disorder, 5000 pregnant women rated as having a high risk for babies wih this disorder were recruited and tested. These were the results:

----------------------- Born with Disorder --- Born without disorder---total
Tested Positive----- 200---------------------475---------------------------675
Tested negative-----50----------------------4275--------------------------4325

Totals--------------250-----------------4750---------------------5000

for each item below, choose the single most appropriate figure (rounded by two decimal points) from the above list. Each option may be used once, more than once, or not at all.

Item1:
The percentage chance of a woman with a positive screening test having a child affected by the disorder.

Item2:
The positive predictive value.

rpeevor · Joined: 27 Aug 2006 Posts: 28

we covered this Q 6/12 ago.. it is completely wrong - the answers are wrong both in the numbers and explanations.. just ignore it and move on...

Nick Raine-Fenning · Posted: Wed Apr 18, 2007 4:07 pm Post subject:

But the newcomers may not be aware so it is important as errors like this throw you and sometimes take you even longer to realise / work out why they are wrong!
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Xerxes I · Posted: Thu Mar 27, 2008 4:27 pm Post subject:

This is not an EMQ but I thought maybe an exercise in basic stat calculation would be nice.

I have taken this from the college guideline on Placenta praevia.

Chou et al. prospectively followed 80 women with persistent placenta praevia using transabdominal B-mode and colour Doppler ultrasonography, with 17 cases of accreta identified at delivery. Doppler imaging identified 16 cases of suspected accreta, of which 14 were correct with two false positives, and it failed to diagnose the three other cases of accreta, giving a sensitivity of ..... and a specificity of .......The positive and negative predictive values were ......and ....., respectively.

You can check your results by clicking here . page 3 near the end of the page.