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Approach to Thrombocytopenia or low platelet count on

definitions –Count below the 2.5 th lower percentile of the normal platelet count distribution.
Traditional cut-off is < 150 x 109
 National Cancer Institute – severity criteria

 Grade 1 From 75000 to 150 , 000 Grade 2 From 50,000 to < 75,000 Grade 3 From 25,000 to < 50, 000 Grade 4 Below 25,000

Causes- Decreased production Marrow failure -
○ Aplastic anaemia
 Marrow infiltration-
○ leukaemias
○ Myelodysplasia
○ myeloma
○ myelofibrosis
○ lymphoma
○ metastatic carcinoma
 Marrow suppression
○ cytotoxic drugs
○ radiotherapy
○ drugs
 HIV Vit D Deficiency Hereditary causes eg
○ hereditary thrombocytopenia

increased destruction Immune-ITP HIT ( heparin induced ) Drug induced antibodies Infection eg
○ other viruses
○ Malaria Post transfusion Connective tissue disease Non-Immune-DIC Sepsis Cardiac valves TTP / HUS
haemolytic uraemic syndrome Cardiopulmonary bypass Kassabach Merrit Syndrome

Pseudothrombocytopenia-Laboratory artifact caused by platelet clumping due to naturally occurring antibodies directed against normally hidden epitopes of platelet surface antigens-Essential to r/o before considering other causes

history-Bruising or bleeding – check particularly about epistaxis , haematuria and menorrhagia or previous episode of heavy bleeding following eg childbirth , dental extraction Ask about recent viral infection Pregnancy- risk of TTP , gestational thrombocytopenia , HELLP Liver disease -Alcohol history , chronic liver disease Medications – any recent change ( drug incuded ), aspirin, quinine , NSAIDs
H2 blockers , paroxetine , furosemide , metronidazole
Herbal remedies Cancer history Travel – Dengue fever , malaria , rickettsial disease Transfusion- autoimmune , post-transfusion Hospitilization ( Heparin induced ) Immunization – MMR , Varicella , influenza H1N1 Infection eg Hepatitis C and HIV Family history of platelet disorders- congenital thrombocytopenia Constitutional symptoms – fever , night sweats or weight loss

Examination-Location and severity of bleeding risk or easy bruising
For example skin , mucous membranes , GI tract , brain , urinary tract and retroperitoneum Skin – check for petechiae , purpura , bruising Eye-Fundoscopy –> CNS bleeding most common cause of death in severe thrombocytopenia Lymph nodes Abdomen-Hepato / splenomegaly Infection , rash Skeletal abnormalities

Further testing-FBC- repeat to confirm Blood film- genuine TCpenia or factitious ( platelet clumping ) Coagulation screen Liver function test including GGT Renal function including creatinine Serum B12 and Folate HIV serology – if risk factors Anti-nuclear factor ( ITP may be 2ary to SLE ), Rh factor , anticardiolipin antibodies , lupus anticoagulant and CXR , Monospot TTP suspected consider – LDH , reticulocyte count , indirect bilirubin ,PT , 
APTT , Fibrinogen , D-Dimer, Serum creatinine LDH Bone marrow biopsy

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