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

1. How to approach thrombocytopenia Robert Stasi Evidence-Based Approach to Cytopenias ; Department of Haematology , St Georges Hospital , United Kingdom
2. Thrombocytopenia in Adults ; A practical approach to Evaluation and Management Sudhir S Sekhon et al
3. CME Topic E Medicine overview of platelet disorders August 2017
4. Assessment of thrombocytopenia BMJ Best Practice
5. Thrombocytopenia in an adult BMJ 2013 ;346 :f3407
6. Investigating an incidental finding of thrombocytopenia BMJ 2013 ;346; f 1 1
7. RACGP -Incidentally detected thrombocytopenia in adults Volume 43 , No 10 , October 2014
8. AAFP Thrombocytopenia 2012
9. Dynamed Plus Approach to the patient with thrombocytopenia
10. Oxford Handbook of Clinical Haematology Quick reference 2013
11. Clinical Practice Guideline on Thrombocytopenia in Pregnancy American Society of Haematology
12. King’s Health Partners Haematology Institute and Network GP Referral Guide Adult Haematology
13. Thrombocytopenia StatPearls Sruthi Jinna et al May 2019