Urokinase　plasminogen　activator　receptor　(uPAR)　exists　in　a　number　of　formats　in　human　plasma,　including　soluble　uPAR　(suPAR)　and　uPAR　fragments.　We　developed　an　ELISA　method　to　detect　specifically　the　active　form　suPAR,　which　binds　to　its　natural　ligand　uPA.　The　intra　CV　and　inter　CV　of　this　ELISA　assay　is　8.5%　and　9.6%　respectively,　and　the　assay　can　recover　99.74%　of　added　recombinant　suPAR　from　10%　plasma.　This　assay　is　quite　sensitive,　capable　of　detecting　down　to　15　pg/ml　of　suPAR,　and　can　measure　suPAR　concentrations　in　the　range　of　0.031-8　ng/ml　with　high　linear　relationship.　Plasma　samples　from　pregnant　women　were　also　measured　for　the　active　form　of　suPAR　with　this　assay,　giving　an　averaged　level　of　139　ng/ml,　slightly　higher　than　the　level　of　pooled　plasma　from　healthy　donors　(0.96　ng/ml).　This　study　demonstrates　the　feasibility　to　measure　the　active　form　of　suPAR,　which　will　likely　have　value　in　clinical　applications.　(C)　2016　Published　by　Elsevier　B.V.