laboratory features
Last reviewed 10/2022
The laboratory features of ITP include:
- thrombocytopenia:
- platelet count less than 100 000 per cubic mm
- no bleeding until less than 50 000 per cubic mm
- spontaneous bleeds may occur when count between 20 - 50 000 per cubic mm
- serious bleeding more likely if the count drops below 20 000 per cubic mm
- platelets may be enlarged - megathrombocytes - produced in response to enhanced destruction.
- bone marrow - normal or increased megakaryocytes - there are no other abnormalities. Bone marrow investigation is mandatory if steriods are to be given, to rule out leukaemia.
- PT, PTT and coagulation time are normal
- if haemorrhage occurs then there is:
- increased WBC with shift to left
- anaemia - reticulocytes
- tests for platelet associated IgG - 95% sensitivity, 50% specificity for increased platelet IgG due to thrombocytopenia