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. 2019 Feb 20;9(2):e022839. doi: 10.1136/bmjopen-2018-022839

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© Author(s) (or their employer(s)) 2019. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

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Guideline to assess level of clinical significance using NNT. Grey diamond refers to the delta value for the threshold ARR or NNT while the black square to the study ARR or NNT. ARR corresponds to the absolute difference between the experimental and control estimates. The inverse of the ARR corresponds to the NNT. The threshold ARR corresponds to the delta value, and the randomised control trial was designed to detect as determined in the sample size calculation. The inverse of the threshold ARR corresponds to the threshold NNT. ARR, absolute risk reduction; LCL, lower confidence limit; NNT, number needed to treat; UCL, upper confidence limit.