(3) What is the compar- ative effectiveness of adjusting LMWH doses based on the results of anti factor Xa concentrations (performed in a manner that ensures accuracy and reproducibility) vs no such monitoring for patients with estimated creatinine clearance values of ,30 mL/min requiring treatment of VTE? Question: For patients with obesity receiving LMWH therapy for treatment of VTE, should clinicians monitor anti factor Xa 27 NOVEMBER 2018 x VOLUME 2, NUMBER 22 ASH 2018 VTE GUIDELINES: ANTICOAGULATION MANAGEMENT 3269 concentration to guide LMWH dose adjustment vs no such monitoring? For patients with obesity receiving LMWH therapy for treatment of VTE, the ASH guideline panel suggests against using anti factor Xa concentration monitoring to guide LMWH dose adjustment (conditional recommen- dation based on very low certainty in the evidence about effects ). Remark: Providers should consider LMWH using doses based on actual body weight (see recommendation 1) and not monitoring anti factor Xa concentrations, similar to the approach used in nonobese patients. Summary of the evidence. We included eligible studies from the most recent systematic review for patients with obesity receiving LMWH for VTE treatment.101 The search was updated from 2014 onward, yielding a total of 7 studies.27,86,93,102-105 No studies directly compared anti factor Xa monitoring to no such monitoring. Included studies were single-arm cohort studies in which patients with obesity receiving LMWH had anti factor Xa concentrations monitored. For the no-monitoring arm, we used a study that reported no anti factor Xa monitoring to determine the risk of major bleeding and VTE events.23 Included studies grouped patients with varying indications for LMWH most commonly patients with acute VTE, atrial fibrillation, and acute coronary syndrome. We used studies with grouped indications for the outcome of major bleeding and rated down the evidence for indirectness. 