Apolipoprotein M and the risk of unprovoked recurrent venous thromboembolism.

Background: Apolipoprotein M (ApoM) protects against atherosclerosis; however, it is unknown whether it also protects against recurrent venous thromboembolism (VTE).

Methods: Patients in the Malmö Thrombophilia Study (MATS) were followed post-anticoagulant treatment until the diagnosis of recurrent VTE or the end of the study (mean follow-up 36 months). Among patients with a first episode of unprovoked VTE, we identified 43 patients (9.7%) with recurrent VTE during the follow-up period. Three age- and sex-matched control subjects without recurrent VTE were selected for each case (n = 129). Plasma levels of ApoM were quantified by a sandwich ELISA method.

Results: Among all patients, the plasma levels (mean ± SD) of ApoM were not significantly different between patients with recurrent (0.70 ± 0.2) and non-recurrent VTE (0.74 ± 0.2), p = 0.2. However, after stratification of data according to gender, male patients with recurrent VTE showed significantly (p=0.02) lower ApoM levels (0.63 ± 0.2) as compared to those with non-recurrent VTE (0.74 ± 0.2). No significant differences in ApoM levels were found between recurrent (0.8 ± 0.2) and non-recurrent VTE (0.75 ± 0.2) in female patients, p = 0.3. Cox-regression analysis showed that the risk of recurrent VTE was 0.98 (95% CI, 0.96-0.99) for each 0.01 μM increase in ApoM level in male patients (p = 0.042), and this risk remained unchanged after adjusting for inherited thrombophilia and body mass index (p = 0.027). ApoM levels were not associated with the risk of recurrent VTE in female patients.

Conclusions: Our results show that levels of ApoM in recurrent VTE may differ according to gender and lower levels of ApoM may predict VTE recurrence in male patients.