Supplementary Material for: A Service Evaluation of Anti-Xa Measurements in Patients with Kidney Impairment in A Tertiary Centre

Background: Pre-emptive dose reduction of low-molecular weight heparins (LMWHs) is often utilised in those with chronic kidney disease (CKD) to prevent bioaccumulation. We report on the association of a pre-emptive dose reduction on anti-Xa range and its correlation with clinical outcomes.

Methods: We undertook a retrospective service evaluation of patients with CKD (eGFR < 30 ml/min/1.73m2) receiving therapeutic dose dalteparin. The primary exposure was dalteparin anti-Xa trough and peak. Primary outcomes were ISTH-defined clinically relevant bleeding, thrombosis and all-cause mortality within 90 days of LMWH initiation. A multivariate Cox proportional hazards model was employed to assess the relationship between anti-Xa levels and the incidence of bleeding and mortality.

Results: A total of 103 patients were identified over a two year period. Seventy-eight (75.7%) had anti-Xa monitoring done. Trough anti-Xa distribution was within target in 58 (75.6%). Patients on dialysis had a higher incidence of bleeding (19 vs 12, p < 0.05). Patients with bleeding had significantly higher median anti-Xa trough (0.26 vs 0.13 U/mL, p < 0.01). The median time to bioaccumulation was 19 days. In multivariate Cox models, only anti-Xa trough remained an independent association with bleeding (HR: 1.47 per 0.1 U/mL, 95 % CI: 1.05-2.15; p < 0.05). No associations with mortality were identified.

Conclusion: In this report, trough anti-Xa measurement of dalteparin is independently associated with bleeding in patients with CKD. Further prospective, larger studies are warranted to validate these results before it can be universally recommended in clinical practice.