{
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  "path": "/t/decision-analysis-in-clinical-guidelines-net-benefit-nnt-nri/28682#post_1",
  "publishedAt": "2026-03-30T15:56:32.000Z",
  "site": "https://discourse.datamethods.org",
  "tags": [
    "2026 AHA/ACC Lipid Guidelines",
    "AHA Scientific Statement on Clinical Utility"
  ],
  "textContent": "I am a clinician trying to understand the methodological framework behind recent cardiovascular prevention guidelines, specifically the **2026 AHA/ACC Lipid Guidelines** and the accompanying **AHA Scientific Statement on Clinical Utility**.\n\nI have been trying to reconcile how treatment thresholds are set and how new markers are justified for reclassification. I would appreciate the community’s insight on three specific areas:\n\n**1. On the use of NNT-based Net Benefit to set thresholds**\n\nThe guidelines often utilize the Number Needed to Treat (NNT) to conduct a form of net benefit analysis to determine treatment thresholds (e.g., the 3% threshold for statin use as shown below). As a clinician, I’m trying to understand if this is a statistically sound way to define a decision point.\n\n  * I understand that NNT is non-linear and varies with baseline risk. Is it still a reliable “anchor” for population-level guidelines?\n\n  * Are there nuances in the harm/benefit ratio that NNT might overlook compared to a continuous probability-based framework when doing decision analysis curves?\n\n\n\n\n**2. On the role of NRI in justifying clinical tools**\n\nWhile the guidelines use the logic above for thresholds, they often pivot to the **Net Reclassification Index (NRI)** to justify the “added value” of new markers. I am curious about the following:\n\n  * **The Weighting of Events:** How does NRI “reclassify” an existing decision threshold? Are the non-event and a event still weighted equally? Is this considered a valid approach to “reclassification”?\n\n  * **he “Hidden Costs” of the Marker:** Unlike a risk score, a physical test like CAC introduces its own harms—radiation, incidentalomas, and downstream testing (stress tests, etc.). If a tool achieves a 20% NRI but triggers a cascade of low-value downstream procedures, how is that “tax” accounted for?\n\n\n\n\n**3. On the compatibility of these frameworks**\n\nCan these two approaches be used together consistently? We seem to use a decision-analytic framework (Net Benefit/NNT) to establish the threshold, but then evaluate a marker’s utility using a different framework (NRI) that does not appear to incorporate those same clinical weights.\n\n  * Are these frameworks fundamentally incompatible for guideline development?\n\n  * Would a consistent **Decision Curve Analysis** —applying the same weighting of harms and benefits to both the threshold selection and the marker evaluation—be a more appropriate standard?\n\n\n\n\nAny thoughts, comments, or useful references on this would be appreciated. Ultimately, I want to help clinicians like myself work with patients to make informed decisions, and find the best ways to do this.",
  "title": "Decision Analysis in Clinical Guidelines: Net Benefit, NNT, & NRI"
}