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Test ID PSPTM Phosphatidylserine/Prothrombin Antibody, IgM, Serum

Useful For

Detection of IgM antibodies against phosphatidylserine/prothrombin complex in patients with strong suspicion of antiphospholipid syndrome (APS) who are negative for the APS criteria laboratory tests (l(lupus anticoagulant, IgG and IgM anticardiolipin/beta 2-glycoprotein I and anti-beta 2-glycoprotein I antibodies)


May be useful for the evaluation of patients with prior positive lupus anticoagulant results who are on direct oral anticoagulant (DOAC) therapy


May be useful as a risk marker for thrombosis in antiphospholipid antibody carriers

Reporting Name

PS/PT Ab, IgM, S

Specimen Type


Ordering Guidance

Cardiolipin and beta-2 glycoprotein testing are the first-tier test options for most patients. Phosphatidylserine/prothrombin antibodies are considered part of the second-tier workup.

Specimen Required


Preferred: Serum gel

Acceptable: Red top

Specimen Volume: 0.5 mL

Collection Information: Centrifuge and aliquot serum.

Specimen Minimum Volume

0.4 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 21 days
  Frozen  21 days

Reference Values

Negative ≤30.0 U

Borderline 30.1-40.0 U

Positive ≥40.1 U

Day(s) Performed


Report Available

1 to 7 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
PSPTM PS/PT Ab, IgM, S 85358-0


Result ID Test Result Name Result LOINC Value
PSPTM PS/PT Ab, IgM, S 85358-0

NY State Approved


Test Classification

This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.