Phosphatidylserine/Prothrombin (PS/PT) Antibody (IgM)

Also known as: PSPT IgM Antibodies, aPS/PT IgM

Clinical Use

Use

The assay detects IgM-class antibodies targeting the phosphatidylserine–prothrombin complex in serum or plasma. As non‑criteria antiphospholipid antibodies, PS/PT IgM positivity may support diagnosis of antiphospholipid syndrome (APS) and correlate with lupus anticoagulant presence, particularly in patients on anticoagulant therapy where lupus anticoagulant testing may be unreliable. A positive result may stratify thrombosis risk in autoimmune conditions such as APS or systemic lupus erythematosus. Results in IgM units; cutoff ≤ 30 units. Difference in assay methods may limit inter‑laboratory comparability.

Special Instructions

Not provided.

Limitations

There are no standardized international reference materials for PS/PT antibody testing, so results may not be interchangeable across assay methods. Isolated PS/PT IgM near cutoff may reflect acute‑phase responses (e.g., infection) rather than true antiphospholipid antibody positivity. Clinical correlation is required for interpretation.

Test Details

Methodology

Immunoassay (ELISA)

Biomarkers

Phosphatidylserine‑prothrombin complex Ab.IgM

Protein

IgM

Expression • Quantitative (Continuous) (e.g., copies/mL, % expression)

LOINC Codes

Result Codes

85358-0 - PS-prothrom cmplx IgM SerPl IA-aCnc

Result Turnaround Time

1-3 days

Specimen

Plasma

Volume

1 mL

Minimum Volume

0.5 mL

Container

sodium citrate (light blue‑top) tube

Collection Instructions

Collect platelet‑poor plasma: centrifuge light blue‑top tube 15 minutes at approx. 1500 × g within 60 minutes of collection; remove plasma avoiding buffy layer; centrifuge again and transfer platelet‑poor plasma (<10 000/mcL) to plastic vial.