Calculating NNH
•The calculation of NNH is the same as that of NNT, but the interpretation is differentiated by the adverse outcomes present in harm studies. Here the term NNH effectively replaces NNT.
•Similarly Absolute Risk Increase (ARI) is calculated in the same way that ARR is calculated but the intervention increases the amount of harm instead of therapeutic gain.
•NNH = 1/ARI =
1/|CER – EER|