Thrombocytopenia ( Low platelet count )
Approach to Thrombocytopenia or low platelet count on A4Medicine.co.uk
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 ○ HIV ○ 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
Referral -Platelet count < 50 Platelet count 50 -100 in association with other cytopenias / findings as ◘ Hb < 10 ◘ Neutrophils < 1 ◘ splenomegaly ◘ lymphadenopathy Pregnancy related thrombocytopenia Patient with count < 20 or active bleeding -> admit Thrombocytopenia and a previous h/o thrombosis
LINKS AND RESOURCES
A very comprehensive informative page from the National Heart Lung and Blood Institute (NIH) https://www.nhlbi.nih.gov/health-topics/thrombocytopenia
A simple explanation from Labtestsonline UK can be quite helpful https://labtestsonline.org.uk/tests/platelet-count
A very easy to understand explanation from Oneblood Org is also very educative for patients https://www.oneblood.org/media/blog/platelets/what-causes-low-platelet-count.stml
Another simple explanation from Platelets on the web https://www.ouhsc.edu/platelets/platelets/platelets%20intro.html
References
- How to approach thrombocytopenia Robert Stasi Evidence-Based Approach to Cytopenias ; Department of Haematology , St Georges Hospital , United Kingdom
- Thrombocytopenia in Adults ; A practical approach to Evaluation and Management Sudhir S Sekhon et al
- CME Topic E Medicine overview of platelet disorders August 2017
- Assessment of thrombocytopenia BMJ Best Practice
- Thrombocytopenia in an adult BMJ 2013 ;346 :f3407
- Investigating an incidental finding of thrombocytopenia BMJ 2013 ;346; f 1 1
- RACGP -Incidentally detected thrombocytopenia in adults Volume 43 , No 10 , October 2014
- AAFP Thrombocytopenia 2012
- Dynamed Plus Approach to the patient with thrombocytopenia
- Oxford Handbook of Clinical Haematology Quick reference 2013
- Clinical Practice Guideline on Thrombocytopenia in Pregnancy American Society of Haematology
- King’s Health Partners Haematology Institute and Network GP Referral Guide Adult Haematology
- Thrombocytopenia StatPearls Sruthi Jinna et al May 2019