Thread by @tmprowell

Time for some #biostats. Here's how I talk about risk reduction w/ pts in #oncology clinic. If someone says, there's a 50% reduction in the risk, you need to know if they're talking about relative risk or absolute risk.
#COVID19 #MedEd

Tweet #2: I explain relative & absolute risk using coupons. A 50% off coupon on a $1 candy bar is worth 50 cents. A 50% off coupon on a $20,000 car is worth $10,000. If you don't know the starting cost (or in med, the absolute risk), you don't know how valuable 50% off is. #MedEd

Tweet 3: "50%⬇️ in risk" headlines usually mean⬇️in relative risk. To calculate # of ppl needed to treat to benefit 1, you divide 1 by the absolute⬇️in risk. Here, ppl WITHOUT the med had a 2 in 100K (0.002%) risk. Ppl WITH the med had a 1 in 100K (0.001%) risk. #BioStats #MedEd

Tweet 4: Since the risk of dying was only 2 in 100K w/ no med & 1 in 100K w/ the med, if you treat 100K ppl, you'll save 1 life. A 50% ⬇️in relative risk DOES NOT MEAN that if you treat 100K ppl, you save 50K lives. That would only be true if everyone died without the med. #MedEd

Tweet 5/5: To calculate the # of ppl you need to treat to benefit one (for any disease & any treatment), you just need to know the absolute % risk of death (or any other outcome) without the treatment (control) & the % risk w/ it (experimental): omnicalculator.com/health/nnt #MedEd