Test Catalog

Test ID: PSPTG    
Phosphatidylserine/Prothrombin Antibody, IgG, Serum

Useful For Suggests clinical disorders or settings where the test may be helpful

Second-tier 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 IgG antibodies against phosphatidylserine/prothrombin

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

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 Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Negative < or =30.0 U

Borderline 30.1-40.0 U

Positive > or =40.1 U

Interpretation Provides information to assist in interpretation of the test results

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

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

A diagnosis of antiphospholipid syndrome (APS) should not be based only on the presence of antiphosphatidylserine/prothrombin (PS/PT) antibodies.


A negative result for anti-PS/PT antibodies does not exclude the diagnosis of APS.


Anti-PS/PT antibodies are not yet included in the classification criteria for APS.

Clinical Reference Recommendations for in-depth reading of a clinical nature

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