Bleeding tests
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This document provides information on tests used to evaluate bleeding disorders. It describes screening tests like bleeding time, platelet count, prothrombin time, activated partial thromboplastin time and thrombin time that can identify platelet, coagulation factor and fibrinolytic abnormalities. Specialized tests like platelet aggregation, coagulation factor assays and D-dimer are used when screening tests suggest a bleeding disorder. Clinical signs of bleeding disorders in the oral cavity and considerations for dental treatment are also outlined.
Bleeding tests
- 2. INTRODUCTION What Is a bleeding disorder??? General term for a wide range of medical problems that lead to poor blood clotting and continuous bleeding. E.g. Von Willebrand’s disease, haemophilias.
- 4. ORAL FINDINGS Platelet deficiency and vascular wall disorders result in extravasation of blood into connective tissue of mucosa creating small pinpoint haemorrhages called petechiae and large patches called ecchymosis. Platelet disorders with severly altered hemostatsis can result in spontaneous gingival bleeding. Continous oral bleeding over long periods of time can foster deposits of hemosiderin and other blood degradation products on tooth
- 5. Hemarthosis is a common complication in hemophiliacs weight bearing joint yet it rarely occurs in the TMJ. Evaluation of dental disease in a population with bleeding disorders revealed a higher caries rates, a greater number of un restored teeth and severe periodontal disease. Evaluation of dental disease patterns in children with severe haemophilia revealed a significantly lower prevelance of dental caries and low plaque scores as compared to matched healthy controls.
- 8. I) INVESTIGATION OF DISORDERED VASCULAR HEMOSTASIS BLEEDING TIME TEST FOR CAPILLARY FRAGILITY (TORNIQUET TEST)
- 9. BLEEDING TIME Modified Ivy’s test Normal value 1- 6 minutes Indicates time taken for a standardised skin puncture to stop bleeding. Poor indicator of clinically significant bleeding at other sites, hence its use as a predictive screening test for oral surgical procedures has been discouraged. A prolonged bleeding time may be due to following causes: i)Thrombocytopenia ii)disorders of platelet function iii) von Willebrands disease vascular abnormality and factor v and xi deficiency
- 10. TORNIQUET TEST Tourniquet Test for capillary fragility is performed to identify disorders of vascular wall integrity or platelet disorders. Stasis is produced by inflating a sphygmomanometer cuff around the arm in the usual manner.(between 80 – 120mm/hg).
- 11. This moderate degree of stasis is maintained for 5 minutes. 2.5 cm diameter region of skin on the volar surface of the arm 4 cm distal to the antecubital fossa is observed for petechial haemorrhages. Presence of more than 20 petechiae is considered a positive test
- 12. INVESTIGATION OF PLATELET AND PLATELET FUNCTION SCREENING TESTS SPECIAL TESTS • Platelet count • Bleeding time • Examination of fresh blood film to see the morphologic abnormalities of platelets • Platelet adhesion tests • Aggregation tests • Electron microscopy • Prothombin consumption index
- 13. PLATELET COUNT Normal platelet count – 150,000to 450,000/mm3. Platelet count below 10,000/mm3 – platelet transfusion.- To prevent haemmorhagic shock Platelet count <50,000/mm3 – surgical or traumatic haemorrhage. Platelets are more difficult to count due to their small size and its tendency to adhere to foreign surface.
- 14. 3 methods are used to count the number of platelets which includes Direct method- whole blood is diluted and the platelets are counted Semi Automated method -platelets are subjected to sedimentation and coagulation and then counted using electronic particle counter Fully Automated method- platelets are directly counted
- 15. SPECIAL TESTS If the screening test indicate a disorder of platelet function the following tests are carried out i)Platelet adhesion tests such as retention in a glass bead column ii)Aggregation tests which are turbidometric techniques using ADP,collagen or ristocetin
- 16. iii)Granular content of the platelets and their release can be assessed by electron microscopy or by measuring the substances released iv)Platelet Coagulation activity is measured indirectly by prothombin consumption index, which provides information about the first stage of clotting, by measuring the amount of residual serum prothrombin which remains after clotting.
- 17. INVESTIGATION OF BLOOD COAGULATION SCREENING TESTS SPECIAL TESTS • Whole Blood Coagulation Time • Prothrombin Time and INR • Activated partial thromboplastin time • Thrombin Time • Coagulation Factor Assays • Quantitative assay
- 18. COAGULATION TIME Normal range is 4-9 minutes at 37ºC Insensitive and non specific – hence not used It is done by various capillary and tube methods
- 19. PROTHROMBIN TIME Normal range – 11-13 seconds. Its tests the adequacy of extrinsic and common coagulation pathways Increased prothrombin values indicate deficiency of factors v , vii, x, prothrombin or fibrinogen.
- 20. Use : measure the effects of coumarin anticoagulants and reduction of vitamin K dependent Fs II, VII, IX and X Causes of prolonged PT : adminstration of oral anticoagulant drugs, liver disease especially obstructive liver disease, Vitamin K deficiency and DIC
- 21. INTERNATIONAL NORMALISED RATIO INR was introduced by WHO in 1983 INR is based on the ratio of the patient's prothrombin time and the normal mean prothrombin time. Normal coagulation profile is when INR is 1. Evaluates the extrinsic coagulation system and measures the presence or absence of clotting factor i, ii, v, vii and x
- 22. Use : measure the effects of coumarin anticoagulants ,reduction of vitamin k dependant factors ii, vii, ix and x and metabolic aspects of protein synthesis in the liver. It doesnot measure the reduction of factors viii or ix which characterize hemophilias A and B because the extrinsic system uses only these factors. Dental procedures are carried out upto a maximum value of 2.5 above which no surgical procedures are undertaken.
- 23. ACTIVATED PARTIAL THROMBOPLASTIN TIME Normal range :10- 30seconds aPTT is considered normal if the test aPTT and control aPTT are within 10 sec of each other. Use: evaluate intrinsic cascade and measure functional levels of Fs VIII, IX, XI, XII which are the intrinsic system factors. It also measures the factors common to both intrinsic and extrinsic systems (factors x ,v ,prothrombin and fibrinogen.)
- 24. aPTT is altered in haemophilias A and B and with use of anticoagulant heparin. Prolonged aPTT is seen in parentral administration of heparin, disseminated Intravascular coagulation, liver diseases and circulating anticoagulants
- 25. THROMBIN TIME Normal TT – 9-13 sec. Use: Test the ability to form the initial clot from fibrinogen and to measure the activity of heparin or other paraproteins that inhibit conversion of fibrinogen to fibrin. This tests yield abnormal result when the fibrinogen level is below 70 – 100 mg/dl but is unaffected by levels of any other coagulation factor
- 26. Advantages Simple Can be performed quickly Useful in diagnosis of DIC The causes for increased TT value are hypofibrinogenaemia, raised concentration of FDP, presence of Heparin.
- 27. SPECIAL TESTS In the presence of an abnormality in screening tests, detailed investigations for the possible cause is carried out. These include i)Coagulation Factor Assays These are usually based on familiar screening and conformatory tests such as PT and aPTT. Normal range of coagulation factors ranges from 50-150%of normal
- 28. FACTOR IX ASSAY Measures the activity of factor IX -- one of the substances involved in blood coagulation. The test is also known by the names Christmas factor assay; Serum factor IX assay Decreased factor IX activity may be related to: i)Congenital deficiency of factor IX (hemophilia B) ii ) Disseminated intravascular coagulation (DIC) iii) Fat malabsorption iv) Liver disease (such as cirrhosis)
- 29. FACTOR VII ASSAY It is also known by the names proconvertin assay and stable factor assay Decreased factor VII activity may be related to: i)Congenital deficiency of factor vii ii)Fat malabsorption iii)Liver cirrhosis iv)Vitamin K deficiency v)Use of Warfarin
- 30. FACTOR VIII ASSAY A decrease in factor viii is noticed in hemophilia A and also in primary immunodeficiency disease (PID).
- 31. ii) Quantitative assay The coagulation factors can be quantitatively estimated by immunological and various other chemical methods.
- 32. vWF assay It can be assayed by immunological technique or by ristocetin method Ristocetin binds to platelets in vitro and activates vWF receptors on their surface, this leads to platelet aggregation if vWF is available . Thus the ristocetin induced platelets aggregate can be used as an assay for vWF The half life of factor viii in circulation is 12 hours if vWF levels are normal but 24hours
- 33. INVESTIGATIONS OF FIBRINOLYTIC SYSTEMS SCREENING TESTS SPECIAL TESTS i)Estimation of fibrinogen ii)Fibrin Degradation Products iii)Ethanol gelation tests •ELISA • functional assay •immunological assay • chromogenic assays of plasminogen activators
- 34. FIBRIN DEGRADATION PRODUCTS FDPs evaluate the presence of the dimer of fibrinogen and/or fibrin above normal levels. Normal Fibrinogen level – 200-400mg/ dL FDPs are protein fragments of varying size that result from proteolytic action of plasmin on fibrin or fibrinogen. This state can result from primary fibrinolytic disorders or DIC.
- 35. INDICATION FOR A FEW LAB TESTS Identification of a dental patient with or at a risk for a bleeding disorder begins with a thorough review of the medical history. Patient report of a family history of bleeding problem can help identify inherited disorders of hemostasis. A patients past history of bleeding following a surgical procedure can help identify a risk
- 36. Surveying the patient for current medication which may include drugs with haemostatic effect such as coumarin, anticoagulant, heparin, apirin, NSAIDS, is essential Active medical conditions like hepatitis or cirrhosis , renal disease, may predispose patients to bleeding problems. When the history and review systems suggest increased bleeding laboratory studies are warranted Bleeding time is tested in patients with uremia . And also when a clinician needs
- 37. Platelet count is taken in patients with known thrombocytopenia, in patients with easybruising , bleeding from gums when brushing , petechiae, unusual heavy bleeding from nose aPTT is done on patients using heparin, in suspected cases of haemophilia, and when there is easy bruising or bleeding Prothrombin Time in patients with unexplained bleeding, as a screening for patients with bleeding problem prior to surgical procedure and for patients under Warfarin. Thrombin Time is evaluated when heparin contamination suspected and in patients with prolonged clotting time.
- 38. CONCLUSION Patients with bleeding disorders appropriately prepared for preoperatively ,are generally able to withstand dental care as well as the unaffected individuals Consultation with the patients physician is recommended for guidance on management required for high risk dental surgical procedures. When the history and review of systems suggest bleeding propensity laboratory studies are warranted
- 39. BIBLIOGRAPHY Burket’s Oral medicine – 11th edition and 10th edition Wintrobes Clinical haematology -10th edition, part two Robbins basic Pathology -6th edition Essential Pathology For Dental Students by Harsh Mohan -4th edition
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