Sign in →

Test ID: PSPT Phosphatidylserine/Prothrombin Antibody, IgG and IgM, Serum

Useful For

Preferred second-tier panel for the detection of IgG and IgM antibodies against phosphatidylserine/prothrombin complex in patients with strong suspicion of antiphospholipid syndrome (APS) who are negative for the APS criteria laboratory tests (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

Profile Information

Test ID Reporting Name Available Separately Always Performed
PSPTG PS/PT Ab, IgG, S Yes Yes
PSPTM PS/PT Ab, IgM, S Yes Yes

Reporting Name

PS/PT Ab, IgG/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

Clinical Information

According to the 2006 revised Sapporo classification criteria, a diagnosis of antiphospholipid syndrome (APS) is based on the presence of specific pregnancy-related morbidities, arterial or venous thrombosis in association with persistent lupus anticoagulant (LAC), anticardiolipin IgG/IgM or anti-beta 2-glycoprotein I IgG/IgM antibodies.(1) Cardiolipin is an anionic phospholipid that interacts with the protein cofactor beta 2-glycoprotein I. LAC is an indirect assessment for the presence of antiphospholipid antibodies, which is evident in the in vitro prolongation of phospholipid-dependent coagulation.(2) Anticardiolipin and anti-beta 2-glycoprotein I antibodies are detected in solid-phases immunoassays using beta 2-glycoprotein I-dependent cardiolipin/or beta 2-glycoprotein I alone as substrate, respectively.(2,3)


There is evidence from multiple studies to suggest that patients with APS may develop autoantibodies to other phospholipid/protein complexes, specifically phosphatidylserine/prothrombin (PS/PT).(4-9) Like beta 2-glycoprotein-dependent I cardiolipin, PS/PT is a complex composed of the anionic phospholipid phosphatidylserine and the protein cofactor prothrombin. In a systematic review, Sciascia et al demonstrated that the presence of anti-PS/PT IgG antibodies is an independent risk factor for arterial and/or venous thrombotic events, with odds ratio (OR) of 5.11 (95% CI: 4.2-6.3).(4) A multicenter study showed that IgG anti-PS/PT were more prevalent in APS patients (51%) than in those without (9%), OR 10.8, 95% CI (4.0-29.3), p <0.0001.(5) Furthermore, a number of studies have shown clinical and laboratory evidence that PS/PT antibodies may be a useful second-line test for the evaluation of patients at-risk or suspected with suspected APS, particularly for those individuals with evidence of thrombosis or abnormal LAC testing.(6,7) While anti-PS/PT antibodies were highly prevalent and correlated with other anti-PL antibodies, IgG anti-PS/PT conferred a high risk for thrombosis (8,9) but not for pure hematologic involvement.(9) These antibodies may also be seen in patients with other autoimmune diseases such as systemic lupus erythematosus.(5,8) In individuals who test positive for antiphospholipid antibodies without clinical features of APS (carriers), the cumulative incidence rate of thrombotic events has also been reported to be significantly higher for anti-PS/PT IgG positive than anti-PS/PT IgM positive subjects.(10)

Reference Values

Negative ≤30.0 U

Borderline 30.1-40.0 U

Positive ≥40.1 U


A positive and persistent result for anti-phosphatidylserine/prothrombin complex IgG and/or IgM antibodies may be suggestive of a diagnosis of antiphospholipid syndrome (APS) in patients with evidence of arterial, venous, or specific pregnancy-related morbidities. These antibodies may also exist prior to the occurrence APS clinical manifestations as well as in patients with other systemic autoimmune diseases such systemic lupus erythematosus (SLE).


Anti-phosphatidylserine/prothrombin complex IgG antibodies have relatively higher correlations with positive results for lupus anticoagulant than the IgM isotype as well as significant risk for APS-associated thrombotic events compared to the IgM isotype in antiphospholipid antibody carriers.


A negative result does not exclude the diagnosis of APS, as other phospholipid/protein antibodies are also associated with this disorder.

Clinical Reference

1. Miyakis S, Lockshin MD, Atsumi T, et al: International consensus statement on an update of the classification criteria for definite antiphospholipid syndrome (APS). J Thromb Haemost. 2006 Feb;4(2):295-306. doi: 10.1111/j.1538-7836.2006.01753.x

2. Pengo V, Bison E, Denas G, Jose SP, Zoppellaro G, Banzato A: Laboratory diagnostics of antiphospholipid syndrome. Semin Thromb Hemost. 2018 Jul;44(5):439-444. doi: 10.1055/s-0037-1601331

3. Tebo AE: Laboratory evaluation of antiphospholipid syndrome: An update on autoantibody testing. Clin Lab Med. 2019 Dec;39(4):553-565. doi: 10.1016/j.cll.2019.07.004

4. Sciascia S, Sanna G, Murru V, Roccatello D, Khamashta MA, Bertolaccini ML: 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 Feb;111(2):354-364. doi: 10.1160/TH13-06-0509

5. Amengual O, Forastiero R, Sugiura-Ogasawara M, et al: Evaluation of phosphatidylserine-dependent antiprothrombin antibody testing for the diagnosis of antiphospholipid syndrome: results of an international multicentre study. Lupus. 2017 Mar;26(3):266-276. doi: 10.1177/0961203316660203

6. Heikal NM, Jaskowski TD, Malmberg E, Lakos G, Branch DW, Tebo AE: Laboratory evaluation of anti-phospholipid syndrome: A preliminary prospective study of phosphatidylserine/prothrombin antibodies in an at-risk patient cohort. Clin Exp Immunol. 2015 May;180(2):218-226. doi: 10.1111/cei.12573

7. Nakamura H, Oku K, Amengual O, et al: First-line, non-criterial antiphospholipid antibody testing for the diagnosis of antiphospholipid syndrome in clinical practice: A combination of anti-beta 2 -glycoprotein I domain I and anti-phosphatidylserine/prothrombin complex antibodies tests. Arthritis Care Res (Hoboken). 2018 Apr;70(4):627-634

8. Radin M, Foddai SG, Cecchi I, et al: Antiphosphatidylserine/prothrombin antibodies: An update on their association with clinical manifestations of antiphospholipid syndrome. Thromb Haemost. 2020 Apr;120(4):592-598. doi: 10.1055/s-0040-1705115

9. Nunez-Alvarez CA, Hernandez-Molina G, Bermudez-Bermejo P, et al: Prevalence and associations of anti-phosphatidylserine/prothrombin antibodies with clinical phenotypes in patients with primary antiphospholipid syndrome: aPS/PT antibodies in primary antiphospholipid syndrome. Thromb Res. 2019 Feb;174:141-147. doi: 10.1016/j.thromres.2018.12.023

10. Tonello M, Mattia E, Favaro M, et al: IgG phosphatidylserine/prothrombin antibodies as a risk factor of thrombosis in antiphospholipid antibody carriers. Thromb Res. 2019 May;177:157-160. doi: 10.1016/j.thromres.2019.03.006

Day(s) Performed


Report Available

1 to 7 days

CPT Code Information

86148 x 2

LOINC Code Information

Test ID Test Order Name Order LOINC Value
PSPT PS/PT Ab, IgG/IgM, S 97026-9


Result ID Test Result Name Result LOINC Value
PSPTM PS/PT Ab, IgM, S 85358-0
PSPTG PS/PT Ab, IgG, S 85359-8

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.
Mayo Clinic Laboratories | Hematology Catalog Additional Information: