Overview

• Platelet factor 3 (PF3) test detects platelet damage caused by antibody, therefore indirect test for antibody.
• More direct tests: anti-megakaryocyte antibody and more recent anti-platelet antibody test.

Sampling

Tests

Methodologies

Platelet-associated antibody tests

• Immunofluorescence, ELISA, radioimmunoassay, electron microscopy using a staphylococcal protein A-colloidal gold conjugate, flow cytometry.
• Direct methods: use whole blood, EDTA sample.
• Indirect methods: sample serum or plasma tested against pooled normal platelets.

Anti-megakaryocyte antibody test

• Detects megakaryocyte-associated immunoglobulin.
• Positive test may also suggest presence of antibodies against platelets.
• May be more sensitive than PF3 test.

Platelet factor 3 test

• Platelets damaged by antibody release increased PF3.
• Determined by accelerated activated partial thromboplastin time (APTT).
• Indirect.
• Rarely used due to many false negatives.

Availability

• Limited in UK.
• Cambridge University Vet School (UK) performs antibody test (EDTA sample).

Validity

Sensitivity

• Direct anti-platelet antibody tests: low sensitivity due to low numbers of platelets.
• Indirect tests: 70-95% sensitive.

Specificity

• Indirect tests: false positives in patients with other immune-mediated diseases, non-immune-mediated thrombocytopenia, neoplasia.

Technique (intrinsic) limitations

• Absolute confirmation of immune-mediated disease.
• Information about source of anti-platelet antibody.

Technician (extrinsic) limitations

• Depends on method used.

Result Data

Further Reading

Publications

Refereed papers

• Recent references from VetMedResource and PubMed.
• Campbell K L et al (1984) Application of the enzyme-linked immunosorbent assay for the detection of anti-platelet antibodies in dogs. Am J Vet Res 45, 2561.
• McVey D S & Shuman W S (1989) Detection of antiplatelet immunoglobulin in thrombocytopenic dogs. Vet Immuno Immunopathol 22, 101.