Purpura, easy bruising, mucocutaneous bleeding (adult, child)

• No tests before treatment: call the emergency medical service (SAMU-Centre 15).
• Ceftriaxone without delay, preferably intravenous, otherwise intramuscular: 1 to 2 g in adults; 50 to 100 mg/kg not exceeding 1 g in children (cefotaxime if ceftriaxone is not available).
• Blood culture or blood sample only if it does not delay the antibiotic.

Laboratory tests the same day

• FBC with platelets and blood film examination
• Serum creatinine with eGFR

Urine tests

• Urine dipstick (proteinuria, haematuria)
• Urine protein:creatinine ratio (spot sample) (if dipstick positive for protein)if needednon-French guidelineVascular purpura (normal platelets) with proteinuria on dipstick: quantification guides management (renal biopsy, nephrology advice) in IgA vasculitis ^[6].

• First a standardised bleeding questionnaire (personal and family): tests are useful only if it suggests a haemostasis disorder.

Laboratory tests (citrate tube, away from a bleed, an infection or a pregnancy)

• FBC with platelets
• PT, aPTT
• Fibrinogen
• Screen for von Willebrand disease: von Willebrand factor activity and factor VIII (the laboratory scientist adds the antigen if needed)
• CRP (if inflammation is possible, to interpret von Willebrand factor)if neededPossible inflammatory context: an inflammatory syndrome raises von Willebrand factor and can mask von Willebrand disease ^[1].
• ASTif needednon-French guidelinePossible liver disease: the German recommendation (DGHO, 2025) and the Scottish NHS Lothian guide look for an acquired cause with liver function tests, the liver synthesising the clotting factors ^[9,10]. The French PNDS on von Willebrand disease does not address this point ^[1].
• ALTif needednon-French guidelinePossible liver disease: the German recommendation (DGHO, 2025) and the Scottish NHS Lothian guide look for an acquired cause with liver function tests, the liver synthesising the clotting factors ^[9,10]. The French PNDS on von Willebrand disease does not address this point ^[1].
• Serum creatinine with eGFR (if renal failure is possible)if needednon-French guidelinePossible renal failure: the German recommendation (DGHO, 2025) and the Scottish NHS Lothian guide also look for this acquired cause, uraemia impairing platelet adhesion and aggregation ^[9,10]. The French PNDS on von Willebrand disease does not address this point ^[1].
• TSH (if signs of hypothyroidism)if needednon-French guidelineSigns of hypothyroidism: the German recommendation (DGHO, 2025) and the Scottish NHS Lothian guide cite the thyroid, hypothyroidism being associated with impaired platelet function and a prolonged bleeding time ^[9,10]. The French PNDS on von Willebrand disease does not address this point ^[1].
• Serum ferritin (if heavy periods, repeated bleeding or microcytic anaemia)if needednon-French guidelineRepeated bleeding: the German recommendation (DGHO, 2025) has iron assessed, a hypochromic microcytic anaemia reflecting repeated losses, especially with heavy periods ^[9]. The French PNDS deals with associated iron deficiency, without including it in the initial work-up ^[1].
• Serum protein electrophoresis (if bruising or bleeding starting after 40 years without a cause found)if needednon-French guidelineAcquired disorder after age 40: the Scottish NHS Lothian guide then asks for electrophoresis, and the German recommendation (DGHO, 2025) cites it among the possible tests, a monoclonal gammopathy being able to cause acquired von Willebrand disease ^[9,10]. The HAS (French National Authority for Health) does not cite bruising among its indications for first-line prescription ^[11].
• State the ABO blood group on the prescription if known (blood group card).
• ABO blood group (only if not known, to interpret von Willebrand factor)if neededPatient’s blood group unknown: von Willebrand factor is interpreted according to ABO group, its levels being 25 to 35% lower in group O subjects ^[12,13]. Do not request it routinely: the diagnostic thresholds (< 30%, or < 50% in a patient who bleeds) apply whatever the group ^[14].
• State on the prescription any anticoagulant, antiplatelet or NSAID.