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  "path": "/t/decision-analysis-in-clinical-guidelines-net-benefit-nnt-nri/28682#post_6",
  "publishedAt": "2026-04-01T21:26:51.000Z",
  "site": "https://discourse.datamethods.org",
  "tags": [
    "Lots has been said about the merits and demerits of NRI in prior discussions",
    "Rather, they are weighted in proportion to their occurrence",
    "One can modify this default weighting if need be"
  ],
  "textContent": "  1. It’s reasonable to anchor treatment decisions on whether the anticipated absolute risk reduction (which is ultimately what the NNT really is) exceeds a certain threshold (what goes into determining that threshold is of course a different manner. In this case it was the risk of diabetes, in others there may be things like cost/other side effect considerations). I’d also keep in mind that the guidelines do advocate for a continuous probability-based framework (i.e., calculating 10-year risk and basing the strength of the treatment recommendation on said risk).\n\n  2. A.Lots has been said about the merits and demerits of NRI in prior discussions. Coming to the point of risk thresholds and weights, the NRI has little bearing on the former. You can not use an NRI to state the risk threshold should be changed or reclassified to some other risk threshold. The risk threshold is something you have prior to calculating an NRI. For weights, the answer is that they are generally not weighted equally. Rather, they are weighted in proportion to their occurrence. For example, if you have a 10% event rate in a cohort, you’d be assuming that events are 9x as important as non-events (90% to 10%). In other words, a single patient (with an event) who is correctly up-classified in risk based on a new marker would be worth incorrectly up-classifying the risk of 9 patients (without an event). One can modify this default weighting if need be, although most investigators go with the default.\n\nB. The tax is not accounted for by the NRI. The intrinsic cost of a CAC scan, the associated radiation, and potentially harmful downstream testing/procedures are ignored. That’s not the fault of the NRI per se, since incorporating these things would involve assigning actual disutilities to said cost/radiation/unnecessary procedures.\n\n     3. I think the frameworks serve different purposes. A decision curve analysis can not give you a threshold to use. It can only evaluate net benefit across a range of thresholds (and a marker may yield net benefit up to a certain threshold and net harm thereafter; the curve itself will not tell you which of these thresholds you should use). The guideline writers have to use some other way to come up with the thresholds they need (in this case, that way was ASCVD event reduction offsetting the increase in diabetes).\n\n",
  "title": "Decision Analysis in Clinical Guidelines: Net Benefit, NNT, & NRI"
}