HSL Special Coagulation

Factors that significantly affect the performance of the examination or interpretation of results

• Underfilled or overfilled citrate tubes so that the ratio of anticoagulant to blood is less or greater than 1:9.
• Clotted samples.
• Haemolysed samples as a result of mixing tubes too vigorously, using the wrong size tube, using the wrong size needle or when the blood is drawn too slowly.
• Heparin-contaminated samples (unless for monitoring heparin levels).
• Presence of DOACS (unless for monitoring) – e.g. Rivaroxaban, Apixaban, Edoxaban, Dabigatran, Argatroban.
• Presence of anti-platelet or non-steroidal drugs prior to platelet function testing (unless used for the detection of the drug).
• Out-of-date citrate tubes.
• Samples for coagulation tests greater than 4 hours old.
• Samples for INR greater than 6 hours old.
• Chylomicrons causing lipaemic samples can interfere with the measurement of platelet aggregation studies and therefore the test should not be performed shortly after a fatty meal.
• Patient samples with low platelet counts (<80–100 x10⁹/dL) for platelet function investigations. When platelet investigations are required for patients with platelet counts <80 x10⁹/L, please inform the laboratory.
• Factors affecting platelet function can include: :
• Foods: e.g., garlic, alcohol, onions, peppers and ginger affect platelet function.
• Drugs: A comprehensive list for patient preparation is outlined in the BSH Clinical and laboratory diagnosis of heritable platelet disorders in adults and children: a British Society for Haematology Guideline (2021 (https://onlinelibrary.wiley.com/doi/epdf/10.1111/bjh.17690)
• Examples include:
  • Non-steroidal anti-inflammatory drugs – aspirin; reversible cyclooxygenase inhibitors such as indomethacin, ibuprofen, sulindac and naproxen.
  • Antibiotics, penicillins, cephalosporins, nitrofurantoin, Miconazole Thienopyridines – Ticlopidine, clopidogrel.
  • GPIIb/IIIa antagonists – Abciximab, tirofiban, eptifibatide.
  • Drugs that affect platelet cAMP levels – Prostacyclin, iloprost, dipyridamole, cilostazol.
  • Anticoagulants and fibrinolytic agents – heparin, streptokinase, tissue plasminogen activator, urokinase, e-aminocaproic acid.
  • Cardiovascular drugs – nitroglycerin, isosorbide dinitrate, propranolol, nitroprusside, nifedipine, verapamil, diltiazem, quinidine.
  • Volume expanders – Dextran, hydroxyethyl starch.
  • Psychotropic drugs and anesthetics – psychotropic drugs: imiprimine, amitriptyline, nortryptaline, chlorpromazine, flufenazine, trifluoperazine and haloperidol.
  • Anesthetics – dibucaine, tetracaine, metycaine, cyclaine, butacaine, nepercaine, procaine, cocaine, plaquenil and halothane.
  • Chemotherapeutic agents – Mithramycin, daunorubicin, BCNU.
  • Miscellaneous drugs – serotonin antagonists, antihistamines, Radiographix contrast agent, foods and food additives.

Patients should be advised to avoid taking these medications for up to 14 days before the test, asked about their current medication and diet prior to obtaining blood samples for these tests.