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- Direct Platelet Antibodies
- Platelet-associated Immunoglobulin
Platelet-associated antibodies to platelet-specific glycoproteins IIb/IIIa, Ib/IX, and Ia/IIa
Detect the presence of an autoantibody that has been associated with autoimmune thrombocytopenic purpura (AITP)
This assay is not designed to detect antibodies associated with heparin-induced thrombocytopenia (HIT), the most common drug-induced immune thrombocytopenia. While a positive result is useful in supporting the diagnosis of ITP, negative results do not necessarily rule out the condition.
Solid-phase enzyme-linked immunoassay after elution of antibodies from platelets
Autoimmune thrombocytopenic purpura (AITP) occurs when platelet autoantibodies destroy an individual's platelets, resulting in a persistent thrombocytopenia.1 In children, AITP is usually self-limiting and frequently resolves spontaneously.2 AITP in children is often associated to a transient viral infection. Approximately 15% of childhood AITP cases become chronic.1 AITP in adults often has an insidious onset, resulting in chronic thrombocytopenia that rarely remits spontaneously.1,2 This condition can be idiopathic or, in some cases, associated with another autoimmune condition (ie, SLE) or malignancy.2
This platelet autoantibody panel is designed to detect IgG antibodies that are bound to platelet-specific glycoproteins llb/llla, lb/IX, or la/lla.3 Antibodies directed against endogenous platelet membrane antigens have been associated with AITP by several laboratories.3-8 A recent study reported that testing for platelet-associated antibodies to llb/llIa, lb/lX, and la/lla had a sensitivity of 53% and a specificity of 72% for diagnosing AITP.3 These results are consistent with the findings from previous studies showing sensitivity ranging from 49% to 66% and specificity ranging from 78% to 92% using assays to detect platelet-associated antibodies to platelet-specific glycoproteins llb/llla and lb/lX.4,5
Tests that measure antibodies to specific platelet antigens have been shown to provide clinical information that is superior to older assays that measured total platelet-associated immunoglobulin G; assays that have often been referred to as PAIgG assays.3-9 While PAIgG assays are frequently positive in patients with AITP, they are also often positive in patients with nonimmune thrombocytopenic disorders.5-9 In contrast to the older PAIgG assays, the platelet antigen specific panel has been shown to have a relatively high positive predictive value of 90%;3 however, the platelet antigen specific panel has been shown to have a low negative predictive value of 24%, indicating that a negative value should not be interpreted as ruling out the condition.3
12 mL (4 mL in each of three tubes)
Lavender-top (EDTA) tube
Maintain specimen at room temperature.
Causes for Rejection
Hemolysis; specimen more than 72 hour old
- 1. Norton A, Allen DL, Murphy MF. Review: Platelet alloantigens and antibodies and their clinical significance. Immunohematol. 2004; 20(2):89-102. 15373657
- 2. Roback JD, Grossman BJ, Harris T, et al, eds. American Association of Blood Banks. Technical Manual. 17th ed. Bethesda, Md: AABB Press; 2011.
- 3. Davoren A, Bussel J, Curtis BR, Moghaddam M, Aster RH, McFarland JG. Prospective evaluation of a new platelet glycoprotein (GP)-specific assay (PakAuto) in the diagnosis of autoimmune thrombocytopenia (AITP). Am J Hematol. 2005 Mar; 78(3):193-197. 15726595
- 4. Warner MN, Moore JC, Warkentin TE, Santos AV, Kelton JG. A prospective study of protein-specific assays used to investigate idiopathic thrombocytopenic purpura. Br J Haematol. 1999 Mar; 104(3):442-447. 10086776
- 5. Brighton TA, Evans S, Castaldi PA, Chesterman CN, Chong BH. Prospective evaluation of the clinical usefulness of an antigen-specific assay (MAIPA) in idiopathic thrombocytopenic purpura and other immune thrombocytopenias. Blood. 1996 Jul; 88(1):194-201. 8704174
- 6. Kiefel V, Freitag E, Kroll H, Santoso S, Mueller-Eckhardt C. Platelet autoantibodies (IgG, IgM, IgA) against glycoproteins IIb/IIIa and Ib/IX in patients with thrombocytopenia. Ann Hematol. 1996 Apr, 72(4):280-285. 8624385
- 7. McMillan R, Wang L, Tani P. Prospective evaluation of the immunobead assay for the diagnosis of adult chronic immune thrombocytopenic purpura (ITP).J Thromb Haemost. 2003 Mar; 1(3):485-491. 12871454
- 8. Fabris F, Scandellari R, Ruzzon E, Randi ML, Luzzatto G, Girolami A. Platelet-associated autoantibodies as detected by a solid-phase modified antigen capture ELISA test (MACE) are a useful prognostic factor in idiopathic thrombocytopenic purpura. Blood. 2004 Jun 15; 103(12):4562-4564. 14976036
- 9. Kelton JG, Murphy WG, Lucarelli A, et al. A prospective comparison of four techniques for measuring platelet-associated IgG. Br J Haematol. 1989 Jan; 71(1):97-105. 2917134
|Order Code||Order Code Name||Order Loinc||Result Code||Result Code Name||UofM||Result LOINC|
|014102||Platelet Autoantibody Panel||014103||Plt Associated Anti-IIb/IIIa||48504-5|
|014102||Platelet Autoantibody Panel||014104||Plt Associated Anti-Ib/IX||48503-7|
|014102||Platelet Autoantibody Panel||014105||Plt Associated Anti-Ia/IIa||48502-9|