In an analysis of observational studies not included in the measured peak enoxaparin anti factor Xa concentrations were found to be within the therapeutic range defined by the individual studies following a therapeutic enoxaparin dose (1.5 mg/kg once daily or 1 mg/kg twice daily).86,93,102,103 In another observational dalteparin anti factor Xa concentrations fell within the defined therapeutic range (between 0.5 and 1.0 units per milliliter for twice-daily dosing and between 1.0 and 2.0 units per milliliter for once-daily dosing) following a therapeutic dalteparin dose (200 units per kilogram per day) (assessed with peak anti factor Xa concentration).105 It was difficult to put these results into perspective given the lack of a control group where LMWH doses were not adjusted based on anti factor Xa concentrations. Harms and burden. After indirect comparison of the available evidence from separate studies, it appears that adjusting LMWH doses based on monitoring anti factor Xa concentrations for patients with obesity may increase the risk of recurrent PE (RR, [95% CI, 4 fewer to 245 more episodes per 1000]; very low certainty) and DVT (RR, 1.53 [95% CI, 0.14-16.61]; ARR, 5 more episodes per 1000 [95% CI, 9 fewer to 162 more episodes per 1000]; very low certainty), but the estimates are imprecise, and CIs include large reductions and very large increases in events. Results also suggested the possibility of increased risk of major bleeding, but again, the CI includes no difference and a very large increase in bleeding (RR, 3.91 [95% CI, 0.67-22.95]; ARR, 30 more episodes per 1000 [95% CI, 3 fewer to 227 more episodes per 1000]; very low confidence). Other EtD criteria and considerations. 