Synonym

• APA
• APLA

Tubes

• Light blue top tube (3.2% sodium citrate tube)
• 4-5 mL of venous blood

Additional information

Deliver to the laboratory within 2 hr of specimen collection

Info

• Antiphospholipid antibodies are autoantibodies that react with serum proteins that are bound to phospholipids
• They cause vasculopathy and thrombosis leading to complications such as
• Deep venous thrombosis
• Gangrene
• Heart attack
• Miscarriage
• Pulmonary emboli
• Stroke
• Commonest form of antiphospholipid antibodies include:
• Anti-beta2 glycoprotein I
• Anti-cardiolipin antibody
• Anti-phoshatidylcholine
• Anti-phosphatidylethonalamine
• Anti-phosphatidylserine
• Lupus anticoagulant

Clinical

Antiphospholipid antibodies (aPL) cause thrombotic diseases and recurrent pregnancy loss.

The antiphospholipid test is done:

• In patients who show symptoms of thromobotic episodes like pain and swelling in the extremities, shortness of breath and headaches
• In women with recurrent abortions
• As a follow up of thrombocytopenia and prolonged activated plasma thromboplastin time (aPTT)

Antiphospholipid syndrome (APS) is a condition where antiphospholipid antibodies are present in a patient who has blood clots, stroke, pregnancy loss, or other related conditions. The formal classification criteria of APS includes at least one of the clinical criteria and one of the laboratory criteria listed below must be met to make a definite diagnosis of APS.

I. Clinical criteria:

1. Vascular thrombosis
1. One or more thromobotic episodes in the artery, vein or capillary of any tissue or organ
2. Pregnancy morbidities
1. One or more unexplained death of a morphologically normal fetus = 10 weeks of gestation OR
2. One or more premature birth of a morphologically normal fetus at = 34 weeks of gestation, due to severe preeclampsia, eclampsia or placental insufficiency OR
3. Three or more unexplained consecutive spontaneous abortions at < 10 weeks of gestation, with the chromosomal causes and the maternal anatomic and hormonal causes being excluded

II. Laboratory Criteria:

1. Medium or high titer of anticardiolipin antibody of IgM or IgG type present in the blood on two or more occasions at least 6 weeks apart
2. Lupus anticoagulant present in the blood on two or more occasions at least 6 weeks apart, detected according to guidelines set by the International Society for Thrombosis and Hemostasis

Features seen with APS but not included in the classification criteria include:

• Dermatological
• Cutaneous Necrosis
• Livedo reticularis
• Painful purpura
• Splinter hemorrhages
• Superficial Thrombophlebitis
• Hematological
• Coombs positive hemolytic anemia
• Thrombocytopenia
• Obstetrical
• Decreased amniotic fluid
• Fetal growth retardation
• Intrauterine fetal death
• Late abortions
• Pre-eclampsia
• Other conditions
• Avascular necrosis of bone in the absence of other risk factors
• Neurological manifestations
• Chorea
• Dementia (rarely)
• Guillain Barre syndrome
• Migraine headaches
• Seizures
• Transverse myelitis
• Pulmonary hypertension
• Unexplained adrenal insufficiency
• Valvular heart disease
• Vascular
• Arterial thrombosis
• Aortic or mitral insufficiency
• Digital ulcers
• Gangrene
• Myocardial infarction
• Retinal artery occlusion
• Stroke
• Venous thrombosis
• Ascites (Budd Chiari syndrome)
• Deep vein thrombosis
• Renal vein thrombosis
• Retinal vein thrombosis
• Pulmonary emboli

Additional information:

• Antiphospholipid antibodies act against serum phospholipid binding proteins, the most common of which is the ß₂-glycoprotein I. Other proteins include prothrombin, protein C, proteinS and annexin V.
• Some antiphospholipid antibodies also bind to negatively charged phospholipids.
• The test is also done to find out the cause for a positive VDRL/RPR test for syphilis. The reagents used to test syphilis contain phospholipids that can cause a false positive result in patients with antiphospholipid antibodies.
• There are two main antiphospholipid antibody tests - immunological tests, like ELISA, and coagulation-based tests for the lupus anticoagulant
• Related laboratory tests, include:
• Anti-beta2 glycoprotein I
• Anticardiolipin antibodies
• Anti-phosphatidylserine
• Anti-prothrombin antibodies
• APTT
• Kaolin clotting time
• Lupus anticoagulant panel
• Platelet neutralization procedure
• Prothrombin time (PT)
• Russell viper venom time

Nl Result

A negative result states that the specific antibody tested is not present at the time of the test. This indicates a normal state.

High Result

A positive result indicates the presence of antiphospholipid antibodies. The titers may be low, moderate or high.

Low to moderate levels of one or more antibodies may occur temporarily due to:

• Aging
• Infection
• Cytomegalovirus infection (Infectious mononucleosis)
• HIV
• Syphilis
• Rheumatoid arthritis

Moderate to high levels of one or more antiphospholipid antibodies seen on 2 occasions, 6 weeks apart, indicates the continued presence of that specific antibody. Such titers are seen in cases of:

• Autoimmune diseases like
• Idiopathic thrombocytopenic purpura
• Sjogren's disease
• Systemic lupus erythematosus
• Malignancy
• Hemopoietic
• Lymphatic

Drugs that may temporarily lead to presence of low to moderate levels of APA include:

• Calcium channel blockers
• Certain antibiotics
• Chlorpromazine
• Hydantoin
• Hydralazine
• Isoniazid
• Phenytoin
• Procainamide
• Quinine
• Thorazine

References

• Cervera R et al. Antiphospholipid syndrome: Clinical and immunologic manifestations and patterns of disease expression in a cohort of 1,000 patients. Arthritis and Rheumatism. 2002;46(4):1019-27
• Chen Q et al. Antiphospholipid antibodies bind to activated but not resting endothelial cells: is an independent triggering event required to induce antiphospholipid antibody-mediated disease? Thromb Res. 2004; 114(2):101-11.
• Hanly JG. Antiphospholipid syndrome: an overview. CMAJ 2003 Jun 24;168(13):1675-82.
• Lab tests online®. Antiphospholipid Antibodies [Homepage on internet]. ©2001-2006. Last reviewed on May 22, 2006. Last accessed on July 13, 2006] Available at URL: http://labtestsonline.org/understanding/analytes/antiphospholipids/test.html
• Laboratory Corporation of America®. Antiphospholipid Antibody Syndrome. [Homepage on internet]© 2003. Last accessed on October 16, 2006. Available at URL: http://www.labcorp.com/coagulation/aps_clinical.html
• Michelle Petri. Lupus Foundation of America Inc. Antiphospholipid Antibodies [Homepage on internet]© 2005. Last updated on February 17, 2005. Last accessed on October 16, 2006. Available at URL: http://www.lupus.org/education/brochures/antiphos02.html