FDA Warns LabCorp about use of OvaSure

| October 10, 2008

http://www.fda.gov/foi/warning_letters/s6947c.htm

I thought this was an interesting commentary:

"FDA aside, what can we tell someone about a screening test that is supposedly 95% sensitive and has a false positive rate of 0.6% among healthy individuals?

Let us assume that the annual figure of 21,000 cases underestimates the number of women with prevalent cancer by 50%, so, for argument’s sake, let’s say there’s 40,000 women with ovarian cancer (rounded off).

If there are 50,000,000 women at risk for ovarian CA (1/3 of our approximately 150,000,000 women), then 0.6% of 50,000,000 is 300,000. So 300,000 women without cancer will test positive.

Let us assume for argument’s sake, that all 40,000 women with ovarian cancer have the same likelihood of testing positive as those who were tested by Yale (a stretch, but probably not by much), so 95% of these, or 38,000 women with ovarian cancer will test positive.

So, in a best case scenario, at the start of screening, just over 10% – 38,000 out of 338,000 women who test positive will have ovarian cancer.

What do you do with this information? Perform ovarian ultrasound?

If the 20,000 "undetected prevalent" cases that I added above have a lower likelihood of testing positive, then positive and negative predictive values will be lower.

If women with "other conditions" (the initial study must have used completely "healthy" individuals as controls) not ovarian cancer, have alterations in these proteins, then the 0.6% figure could rise, further lowering positive predictive values. This says nothing about whether "early" detection will reduce risk of death.

This is NOT to say that this cannot become part of a useful algorithm, but the best way to prevent tests such as these from becoming useful is the commercialize them early with exclusive licenses and dispense with longitudinal studies, etc. Unfortunately, in our economic climate, where the overriding concern is the performance of a stock over the next 15 minutes, it is likely that we will see more of this.  Kudos to the FDA (and another blow to those who say all regulation is bad)."


Category: Government

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