Mendelian Randomization

Davebrid1 — Fri, 31 Jul 2026 21:02:03 GMT

5. Decision Matrix: Which Results to Report: Updated decision tree

@@ Line 90: / Line 90: @@
 print(paste("I^2_GX =", round(i2gx_value, 3)))
 </syntaxhighlight>
 == 4 Selection and Collider Bias (Survival / Ascertainment) ==
@@ Line 163: / Line 204: @@
 == 5. Decision Matrix: Which Results to Report ==
-Use the following adjudication criteria to synthesize the results from the models above.
 {| class="wikitable"
 ! Scenario !! Data Presentation !! Adjudicated Result to Report
 |-
-| '''1. Clean Signal'''
+| '''1. Clean Signal''' || F > 10. Cochran's Q p > 0.05. Egger Intercept p > 0.05. CAUSE Causal Model p < 0.05. || "IVW (Fixed Effects). All assumptions are met."
 |-
-| '''2. Balanced Pleiotropy'''
+| '''2. Balanced Pleiotropy''' || F > 10. Cochran's Q p < 0.05 '''or''' one/few outlier SNPs visible in the scatter/funnel (§3.5). Egger Intercept p > 0.05. || "MR-PRESSO (Outlier Corrected) or IVW (Random Effects). Support with Weighted Median."
 |-
-| '''3. Weak Instruments'''
+| '''3. Weak Instruments''' || Mean F < 10 OR Relaxed criteria (p < 5e-6) used. || "MR-RAPS. Baseline IVW is vulnerable to weak instrument bias."
 |-
-| '''4. Directional Pleiotropy'''
+| '''4. Directional Pleiotropy''' || Egger Intercept p < 0.05 '''or''' clear funnel asymmetry (§3.5). || "Weighted Mode (if I2GX < 0.90) OR MR-Egger Slope (if I2GX >= 0.90). IVW is discarded."
 |-
-| '''5. Correlated Pleiotropy'''
+| '''5. Correlated Pleiotropy''' || CAUSE model comparison p > 0.05 (Sharing Model wins). || "Null Result (Discard Causality). The traits are correlated due to shared genetics, not a direct causal pathway."
 |-
-| '''6. Inconclusive'''
+| '''6. Inconclusive''' || MR-PRESSO removes >30% of SNPs causing power loss, OR Median and Mode significantly contradict each other. || "Unresolved / Inconclusive. State that genetic evidence is too pleiotropic to reliably disentangle."
 |-
-| '''7. Selection/collider bias''' || Both arms present AND predicted bias same sign as observed
+| '''7. Selection/collider bias''' || Both arms present AND predicted bias same sign as observed AND predicted ≈ observed magnitude. || "Report as selection-bias-consistent, not causal. Give uncorrected + corrected estimates."
 |}

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Mendelian Randomization