Alkaline phosphatase in late pregnancy promising biomarker for prediction of post partum VTE

Alkaline phosphatase (ALP) is a glycoprotein found on the cell membrane. It mainly exists in liver, bone, placenta, kidney, small intestine, and other tissues of human. To support fetal growth and development, high ALP levels from placental production are normal variant of pregnancy.

A study published in eClinical Medicine: Lancet, was first of a kind to investigate the associations of ALP levels and Venous thromboembolism (VTE) postpartum, as the related mechanisms remain unclear, they aimed to investigate the associations between ALP levels and VTE postpartum, and to reveal the potential mechanisms

Researchers in a cohort study suggested that serum ALP in late pregnancy could be a promising biomarker for the prediction of VTE postpartum. Low serum ALP levels in late pregnancy were associated with increased risk of VTE postpartum, and the ALP-associated VTE risk may be partially mediated by hemoglobin.

The retrospective cohort study included pregnant women, total of 10,044 participants with serum ALP and whole blood hemoglobin measurements in late pregnancy (median, 37 (35, 39) weeks) were enrolled. The participants’ incidences of VTE (deep venous thrombosis and/or pulmonary embolism) postpartum were confirmed from the medical records. Pregnant women with new-onset VTE postpartum (within 6 weeks after delivery) were confirmed as VTE cases.

The key findings of the study are

• Approximately 0.8% of the pregnant women were diagnosed with VTE postpartum. In the unadjusted model, pregnant women with the lowest quintile of serum ALP levels (≤116 U/L) in late pregnancy had higher risk of VTE postpartum compared with those with the highest quintile (≥199 U/L) (OR, 2.83 [1.32, 6.05]).

• After adjusting for covariates of demographic, life style, birth outcomes, and other liver enzymes, pregnant women with the lowest quintile of serum ALP levels (≤116 U/L) in late pregnancy had increased risk of VTE postpartum compared with those with the highest quintile (≥199 U/L) (OR, 2.48 [1.14, 5.40]).

• A one standard deviation decrease of ln-transformed ALP levels were associated with elevated risk of VTE postpartum (OR, 1.29 [1.02, 1.62]).

• Significant negative associations of ALP with VTE were found in the unadjusted and adjusted models.

• Decreased serum ALP levels significantly (P < 0.05) related to decreased hemoglobin, which was significantly (P < 0.05) related to increased risk of VTE postpartum. Decreased hemoglobin significantly (P < 0.05) mediated 7.59% of ALP-associated VTE postpartum.

Researchers concluded that “This study suggested that low serum ALP levels in late pregnancy were associated with increased risk of VTE postpartum, and the ALP-associated VTE risk may be partially mediated by hemoglobin, suggesting that serum ALP in late pregnancy could be a promising biomarker for the prediction of VTE postpartum.”

Reference: Qian Li, Hongfei Wang, Huafang Wang, Jun Deng, Zhipeng Cheng, Wenyi Lin et al; Association between serum alkaline phosphatase levels in late pregnancy and the incidence of venous thromboembolism postpartum: a retrospective cohort study DOI:https://doi.org/10.1016/j.eclinm.2023.102088.