Hi guys, hoping you'll able to help me out on this one.
I am currently doing a medical school project on a new type of test which has been introduced into our hospital. The test (called NTproBNP) is a screening blood test for heart failure. Patients have this blood test performed, and then have an echocardiogram (ultrasound of the heart) to see how the results compare - echocardiograms are the gold standard test for detecting heart failure. My project involves assessing how accurate the blood test is in identifying patients with heart failure, and calculating parameters relating to the test (sensitivity, specificity, positive and negative predictive values).
My spreadsheet has a cell containing a value, which is the value of the NTproBNP test cut-off - ie, if your test result is above that value, the test is positive, and below, negative. The manufacturers of the test kit suggest that the cut-off should be 14.75. However, if you vary the cut-off, you can improve (or worsen!) how accurate the test is.
At the minute, the spreadsheet uses the 14.75 value, via a few formulae over many cells, to calculate the test parameters. If you change the 14.75 to some other value, certain patients' test results change, which in turn changes the test parameters - the parameters are the results I'm interested in measuring.
What I would like, if possible, is for Excel to produce a graph, say for cut-off values from 1-100, of cut-off value vs sensitivity. Is it possible to get Excel to vary the value for me between 1-100 (instead of making several copies of the sheet to repeat all the calculations at different values of cut-off), and map that against the calculated sensitivity?
Hope this makes sense, I'll be glad to field any questions.
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