Thrombocytopenia (adult, including pregnancy)

• No tests in the community: hospital admission or haematology opinion the same day.
• Platelets < 20 G/L of recent discovery, bleeding, schistocytes on the film, thrombosis on heparin.

In 1 month

• FBC with blood film
• Platelet count on citrate tube
• ASTif neededAlcohol consumption or sign of liver disease: portal hypertension from cirrhosis is a frequent cause of thrombocytopenia in general practice, even without splenomegaly when fibrosis is advanced ^[1], and alcohol is among the causes to look for ^[8].
• ALTif neededAlcohol consumption or sign of liver disease: portal hypertension from cirrhosis is a frequent cause of thrombocytopenia in general practice, even without splenomegaly when fibrosis is advanced ^[1], and alcohol is among the causes to look for ^[8].
• GGTif neededAlcohol consumption or sign of liver disease: portal hypertension from cirrhosis is a frequent cause of thrombocytopenia in general practice, even without splenomegaly when fibrosis is advanced ^[1], and alcohol is among the causes to look for ^[8].

Laboratory tests

• FBC with blood film read by the laboratory scientist, and reticulocyte count
• Platelet count on citrate tube (check for EDTA-induced pseudothrombocytopenia)
• PT, aPTT, fibrinogen
• Haptoglobin
• LDH
• Bilirubin
• CRP
• Serum creatinine
• AST
• ALT
• Serum protein electrophoresis
• HIV serology
• Hepatitis C serology
• Hepatitis B serology
• Antinuclear antibodies (ANA)
• TSH (if signs of thyroid dysfunction)if neededSigns of thyroid dysfunction: the text of the PNDS recommends TSH (possible association with Graves’ disease, usually clinically obvious), but its general practice algorithm does not list it ^[1].
• Vitamin B12if needednon-French guidelineMacrocytosis or setting of deficiency (alcohol, undernutrition): severe vitamin B12 or folate deficiency can cause thrombocytopenia ^[8].
• Folateif needednon-French guidelineMacrocytosis or setting of deficiency (alcohol, undernutrition): severe vitamin B12 or folate deficiency can cause thrombocytopenia ^[8].
• Serum β-hCG (woman of childbearing potential)if needednon-French guidelineWoman of childbearing potential: the international consensus ranks the pregnancy test among the tests of possible usefulness ^[8]; pregnancy changes the interpretation (see the tab “Pregnancy”).

Laboratory tests

• FBC with blood film (schistocytes?) and reticulocyte count
• Platelet count on citrate tube (if clumps on the film)if neededPlatelet clumps on the blood film: exclude spurious thrombocytopenia due to platelet agglutination linked to EDTA; the citrate tube underestimates the count by about 10% ^[1].
• PT, aPTT, fibrinogen
• AST
• ALT
• LDH
• Haptoglobin
• Serum creatinine
• TSH
• HIV serology
• Hepatitis C serology
• Urine protein:creatinine ratio (if BP ≥ 140/90 mmHg)if neededBP ≥ 140/90 mmHg: proteinuria ≥ 0.3 g/24 h with platelets < 100 G/L defines severe pre-eclampsia, to be referred urgently ^[9].
• Antinuclear antibodies (ANA) (depending on the context)if neededSigns suggestive of lupus or connective tissue disease: the international consensus places them “depending on the context” in the work-up of thrombocytopenia in pregnancy ^[8]; they look for secondary ITP (lupus, Sjögren’s syndrome) ^[1].

• Platelets < 20 G/L or mucosal bleeding (Buchanan score > 2): hospital management, haematology opinion within 24 hours.

Laboratory tests

• FBC with blood film (schistocytes, size and appearance of platelets) and reticulocyte count
• Platelet count on citrate tube (if clumps on the film)if neededPlatelet clumps on the blood film: exclude spurious thrombocytopenia due to platelet agglutination in the presence of EDTA, the anticoagulant in the tube ^[10].
• PT, aPTT, fibrinogen
• Serum creatinine
• Urine dipstick (proteinuria, haematuria)
• AST
• ALT
• GGT
• Bilirubin
• Serum immunoglobulins (IgG, IgA, IgM)
• Antinuclear antibodies (ANA) (after 8 years, or earlier if context)if neededRoutine in children over 8 years; before 8 years, only if there is a family history of lupus or a context of immune dysregulation ^[10].
• ABO and RhD blood groupif neededRecommended mainly in severe forms, where a red cell transfusion (or, exceptionally, a platelet transfusion) may become urgent ^[10].
• RAI (severe forms)if neededRecommended mainly in severe forms, where a red cell transfusion (or, exceptionally, a platelet transfusion) may become urgent ^[10].

Platelets between 100 and 150 G/L: in 1 month

• FBC