Absolute risk reduction (ARR) is the difference in risk (not the proportion) attributable to the intervention as compared to a control.
If 8% of people who receive a placebo vaccine develop the flu vs 2% of people who receive a flu vaccine develop the flu, then ARR=8%-2%=6% or 0.06.
The Number needed to treat (NNT) is the number of patients who need to be treated for 1 patient to benefit. A lower number implies a better treatment. It is the inverse of ARR.
If ARR is 0.06, then the NNT for the flu vaccine is 1/0.06=16.66 or about 17 people.
In this question, using the trace element group as a control group, we are asked how many nulliparous women with confirmed pregnancies would have to be treated with folic acid to prevent one congenital abnormality.
Here, 2.3% of people (nulliparous women with confirmed pregnancies) who received the placebo (trace elements) developed a congenital abnormality vs 1.3% of people who received folic acid (the treatment), then ARR=2.3%-1.3%=1% or 0.01.
submitted by โshak360(19)
Absolute risk reduction (ARR) is the difference in risk (not the proportion) attributable to the intervention as compared to a control.
If 8% of people who receive a placebo vaccine develop the flu vs 2% of people who receive a flu vaccine develop the flu, then ARR=8%-2%=6% or 0.06.
The Number needed to treat (NNT) is the number of patients who need to be treated for 1 patient to benefit. A lower number implies a better treatment. It is the inverse of ARR.
If ARR is 0.06, then the NNT for the flu vaccine is 1/0.06=16.66 or about 17 people.
In this question, using the trace element group as a control group, we are asked how many nulliparous women with confirmed pregnancies would have to be treated with folic acid to prevent one congenital abnormality.
Here, 2.3% of people (nulliparous women with confirmed pregnancies) who received the placebo (trace elements) developed a congenital abnormality vs 1.3% of people who received folic acid (the treatment), then ARR=2.3%-1.3%=1% or 0.01.
The NNT is then 1/0.01=100.