Given the low risk of adverse events in stable patients, a very large patient sample will likely be required to answer this question. (2) What is the cost-effectiveness of 6- to 12-week INR recall intervals compared with a 4-week recall interval from the societal perspective? Laboratory monitoring of the anticoagulant response Question: For patients with renal dysfunction (creatinine clearance of ,30 mL/min) receiving LMWH therapy for treatment of VTE, should clinicians monitor anti factor Xa concentration to guide LMWH dose adjustment vs no such monitoring? For patients with renal dysfunction (creatinine clearance of ,30 mL/min) 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 recommendation based on very low certainty in the evidence about effects ). Remark: Instead of monitor- ing anti factor Xa concentrations, providers should consider using doses adjusted for renal function as recommended in product labeling (eg, enoxaparin) or switching to an alternative anticoagulant with lower renal clearance, such as UFH or a different LMWH. Summary of the evidence. We included eligible studies from the most recent systematic review of LMWH for patients with renal The search was updated from 2006 onward, yielding a No studies directly compared anti-Xa monitoring to no such monitoring. Most included studies were single-arm cohort studies in which patients receiving LMWH with renal dysfunction had anti- Xa concentrations monitored. For the no-monitoring comparator group, we used a study that reported no anti-Xa monitoring or dose adjustments (enoxaparin, 1 mg/kg body weight, was administered subcutaneously twice a day) to determine the risk of major bleeding.96 We found no studies that reported the risk of VTE or mortality associated with no anti- Xa monitoring. 