In plain words
Soluble fms-like tyrosine kinase-1, often written sFlt-1, is a protein released by the placenta into the mother's blood. In a typical pregnancy it is present at moderate levels. In , levels are often higher, and the protein can block growth factors that blood vessels need. This is thought to contribute to high blood pressure and kidney changes. Blood tests can measure it alongside another marker, PlGF, and the ratio between them can help clinicians judge risk. A mother may hear about it when she has preeclampsia, is at high risk, or is being followed closely. The number on its own does not diagnose anything. It is one part of a larger picture that the care team reads together.
The deeper version
sFlt-1 is an antiangiogenic soluble splice variant of the VEGF receptor FLT1. It binds vascular endothelial growth factor and placental growth factor (PlGF), reducing their bioavailability. Maynard and colleagues (Journal of Clinical Investigation, 2003) showed in a rat model that placental sFlt-1 produced preeclampsia-like hypertension and , and clinical cohorts have since reported elevated sFlt-1 and reduced PlGF preceding clinical preeclampsia. The sFlt-1 to PlGF ratio is used as a rule-in and rule-out aid in some centers. Soluble endoglin, a related antiangiogenic factor, acts in parallel. Guidelines generally do not use the ratio as a standalone diagnostic test, and its performance across populations remains an open research question.
Where it comes up
What mothers here say about soluble fms-like tyrosine kinase-1
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Sources
- Maynard SE et al. — Excess placental soluble fms-like tyrosine kinase 1 may contribute to endothelial dysfunction, hypertension, and proteinuria in preeclampsia. Journal of Clinical Investigation 2003
- American College of Obstetricians and Gynecologists — Practice Bulletin 222: Gestational hypertension and preeclampsia, 2020