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Test ID: PSPTM Phosphatidylserine/Prothrombin Antibody, IgM, Serum

Useful For

Evaluation of patients with suspected antiphospholipid syndrome


Evaluation of patients with a strong suspicion of antiphospholipid syndrome for whom anticardiolipin/beta 2-glycoprotein I and anti-beta 2-glycoprotein I antibody testing was negative


Evaluation of patients with evidence of a functional lupus anticoagulant


Detection of IgM antibodies against phosphatidylserine/prothrombin

Reporting Name

PS/PT Ab, IgM, S

Specimen Type


Advisory Information

Cardiolipin (CLPMG / Phospholipid (Cardiolipin) Antibodies, IgG and IgM, Serum) and beta-2 glycoprotein (B2GMG / Beta-2 Glycoprotein 1 Antibodies, IgG and IgM, Serum) 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

Clinical Information

A diagnosis of antiphospholipid syndrome (APS) is based on clinical and laboratory evaluation. The clinical manifestations associated with APS include arterial and venous thrombosis and recurrent pregnancy loss. The laboratory testing for APS focuses on assessment for autoantibodies specific for phospholipid/protein cofactor complexes. The current criteria require detection of anticardiolipin, anti-beta 2-glycoprotein I, or lupus anticoagulant (LAC) for classification of APS.


Cardiolipin is an anionic phospholipid that interacts with the protein cofactor beta 2-glycoprotein I. Anticardiolipin and anti-beta 2-glycoprotein I antibodies are detected by immunoassay using the antigen of cardiolipin/beta 2-glycoprotein I or purified beta 2-glycoprotein I, respectively. LAC is an indirect assessment for the presence of antiphospholipid antibodies, which is evident in the in vitro prolongation of phospholipid-dependent coagulation.


There is evidence to suggest that patients with APS may develop autoantibodies to other phospholipid/protein complexes, specifically phosphatidylserine/prothrombin (PS/PT). Similar to cardiolipin/beta 2-glycoprotein I, PS/PT is a complex composed of the anionic phospholipid, phosphatidylserine, and the protein cofactor, prothrombin. A recent systematic review has demonstrated that anti-PS/PT antibodies are a significant risk factor for arterial and venous thrombotic events, with an odds ratio of 5.11 (4.2-6.3). In addition, a separate study indicated that anti-PS/PT antibodies showed the highest correlation with LAC, compared to anticardiolipin or anti-beta 2-glycoprotein I antibodies (p=0.002). Anti-PS/PT antibodies may be a useful additional marker for evaluation of patients with suspected APS, particularly for those individuals with evidence of thrombosis or abnormal LAC testing.

Reference Values

Negative ≤30.0 U

Borderline 30.1-40.0 U

Positive ≥40.1 U


A positive result is consistent with the presence of an antibody specific for the phosphatidylserine/prothrombin complex, and may be consistent with a diagnosis of antiphospholipid syndrome (APS) in patients with evidence of arterial or venous thrombosis or recurrent pregnancy loss.


A negative result is consistent with the absence of an antibody specific for the phosphatidylserine/prothrombin complex. However, this does not exclude the diagnosis of APS, as other phospholipid/protein antibodies are also associated with this disorder.

Clinical Reference

1. Otomo K, Atsumi T, Amenqual O, et al: Efficacy of the antiphospholipid score for the diagnosis of antiphospholipid syndrome and its predictive value for thrombotic events. Arthritis Rheum 2012;64:504-512

2. Hoxha A, Ruffatti A, Tonello M, et al: Antiphosphatidylserine/prothrombin antibodies in primary antiphospholipid syndrome. Lupus 2012;21:787-789

3. Sciascia S, Sanna G, Murru V, et al: Validation of a commercially available kit to detect anti-phosphatidylserine/prothrombin antibodies in a cohort of systemic lupus erythematosus patients. Thromb Res 2014;133:451-454

4. Sciascia S, Sanna G, Murru V, et al: Anti-prothrombin (aPT) and anti-phosphatidylserine/prothrombin (aPS/PT) antibodies and the risk of thrombosis in the antiphospholipid syndrome: A systematic review. Thromb Haemost 2014;111:354-364

5. Heikal NM, Jaskowski TD, Malmberg E, et al: Laboratory evaluation of anti-phospholipid syndrome: A preliminary prospective study of phosphatidylserine/prothrombin antibodies in an at-risk patient cohort. Clin Exp Immunol 2015;180:218-226

Day(s) and Time(s) Performed

Tuesday; Evening

Analytic Time

1 day

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

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 U.S. Food and Drug Administration.
Mayo Clinic Laboratories | Hematology Catalog Additional Information: