Portable INR Analysis Prior to Dental Procedures: Technique Instruction Outcomes for Senior Dental Students

David L. Hall, DDS; and Abdel R. Mohammad, DDS, MS, MPH

Many dental patients receive continuous anticoagulant therapy to prevent thromboembolisms from prosthetic heart valves, dysrhythmias, strokes, deep venous thrombi, and myocardial infarctions.^1-5 Current guidelines recommend that the majority of these patients have minor dental surgical procedures performed without alteration or withdrawal of their anticoagulant therapies.^6-12 The most common standardized test to assess anticoagulant therapy and predict the safety of dental surgery is the international normalized ratio (INR).^12,13 Studies indicate that INR values less than or equal to 3.0,^6-8 3.5,^14-16 or 4.0^9,17,18 are acceptable prior to minor dental surgical procedures.

Portable point-of-care coagulometers are accurate¹⁹ and reliable,²⁰ providing INR results that correlate well with conventional laboratory values.^20-23 Patients prefer them for home^24,25 and clinic²⁶ monitoring.

Previous authors have examined dental school teaching practices regarding anticoagulation and dental procedures,²⁷ evaluated a portable INR testing device in a hospital-based dental practice,¹⁴ and compared portable dental clinic versus laboratory INR values.¹⁵ The current study did not reveal any published reports assessing portable INR technique instruction outcomes for dental students. The objectives of this study were to teach senior dental students to use the INRatio^® (HemoSense, www.hemosense.com) device, to apply the results to actual patients, and to evaluate their outcomes.

Materials and Methods

During the 2008 to 2009 academic year, 105 senior dental students at The Ohio State University College of Dentistry participated in an INRatio training program. INRatio instruction and clinical use was supervised by the faculty from the section of primary care and geriatric dentistry. INRatio training was conducted during a 2-week outreach and engagement experience. Outreach and engagement provided mobile comprehensive dental care to 13 long-term care facilities and numerous community-based healthcare centers. The INRatio education included: 1) a review of an INRatio clinical protocol and dental procedures versus INR guidelines table; 2) completion of a 25-page online INRatio technique training course (https://www.hemosense.com/support/etrainer/sco_01.html); 3) performance of a trial INRatio^® test on another senior dental student; and 4) the use of INRatio for a dental patient taking anticoagulants.

INRatio testing was conducted according to manufacturer’s instructions using an INRatio professional kit. The standard autolance and disposable minipipette (MICROSAFE^® tube, SAFE-TEC Clinical Products, www.safe-tecinc.com) provided by INRatio (Figure 1) were used to obtain capillary blood samples from the lateral plexus of index fingers. Any patient requiring more than one attempt was considered a difficult blood sample.

Patients taking anticoagulants and having minor dental surgical procedures performed were included in this study. Exclusion criteria were as follows: severe liver and/or kidney disease, history of significant bleeding following previous procedures, low platelet count, and a lack of recent (within 24 to 48 hours) laboratory INR test results. Patients’ de-identified INRatio data were collected retrospectively from geriatric outreach charts. Patient information included age, sex, race, anticoagulant and dosage, procedure(s) performed, preoperative and postoperative blood pressure readings, pulse and respiratory rates, immediate and 1-week postoperative hemorrhage results, ease or difficulty of obtaining blood samples, estimated blood loss (EBL), and most recent laboratory INR and preoperative INRatio values. Students were instructed to report any changes in preoperative versus postoperative vital signs greater than 20% and/or any EBL greater than 100 mL. Postoperative hemorrhage was defined as oozing that could not be stopped by biting on gauze and/or requiring intervention. Students completed anonymous written surveys after their geriatric outreach experiences.

The primary outcomes were INRatio results and student survey responses. Secondary outcomes included postoperative hemorrhage and difficulty in obtaining a blood sample. Agreement between patient INRatio and laboratory INR values was analyzed using Cronbach’s α. Student survey results were analyzed independently and compared to mean extramural experience response rates from 2003 and 2006 American Dental Education Association (ADEA) Senior Surveys using Chi-square likelihood ratios with P < .05 significance.

Results

Twelve senior dental students performed INRatio tests on patients taking anticoagulation therapy. Patients’ demographic data, warfarin dosage, EBL, and recent INR and INRatio values are summarized in Table 1. Average warfarin dosage was 4.2 mg. Average EBL was 45 mL (range: 10 mL to 100 mL). The mean of patients’ most recent laboratory INR values was 2.2. The average patient preoperative INRatio was 2.3 (range: 1.3 to 4.0). Laboratory INR and preoperative INRatio results (Cronbach’s α 0.88) corresponded. All patient procedures were completed without postoperative hemorrhage or other serious complications. Of 12 patients taking anticoagulants, 8 required more than one blood sample attempt. No patient experienced changes in vital signs greater than 20% or EBL greater than 100 mL. One elderly female exhibited extensive bruising (ecchymosis) that resolved in 2 to 3 weeks.

A total of 105 senior dental student surveys were evaluated, showing 87% (91 out of 105) (P < .05) agreed that their INRatio training was simple, valuable, and clinically significant. A total of 79% (83 out of 105) of students (P < .05) indicated they would use portable INR testing in their future practices. There were 73% (85 out of 117) (P < .05) who reported difficulty obtaining adequate blood samples from fellow students (78 out of 105) and/or anticoagulated patients (7 out of 12).

Discussion

Studies have shown that the risks of discontinuation of antithrombotic therapy^9,28,29 far outweigh the risks of performing minor dental surgical procedures on these patients.^10,30-32 Therefore, most should have minor dental surgery performed without alteration or withdrawal of their anticoagulants, provided that INR values are within the acceptable range.¹⁷ Studies indicate INR values less than or equal to 3.0,^6,8 3.5,^14-16 or even 4.0^9,17,18 are acceptable prior to minor dental surgical procedures. Preoperative INR testing to assess, verify, and document anticoagulant therapy and predict safety of dental surgical procedures is crucial. INR values for patients taking anticoagulants can be affected by many diseases, drugs, herbs, and foods.^7,16 INR results are also valuable in the diagnosis and treatment of hemorrhage following dental surgical procedures.⁶ The small differences between laboratory INR and INRatio values measured during this study were clinically insignificant.

The methods used to control hemorrhage in anticoagulated patients include: 1) sutures^8,33; 2) gelatin packs and cellulose sponges^33,34; 3) local anesthetic infiltration with vasopressor¹⁶; 4) elimination of inflamed and/or infected granulation tissues^6,35; 5) tranexamic and aminocaproic acid rinses^30,33,36; 6) fibrin glue^33,36; 7) heparin or low-molecular-weight heparin “bridge” therapy^31,37; 8) topical thrombin¹⁶; 9) vitamin K⁷; and 10) protamine.¹⁶

The INRatio device used in this study requires 2 to 3 drops of blood. Other devices such as CoaguChek^® S (Roche Diagnostics, www.coaguchek.com) require a single drop.³⁸ Other researchers have reported difficulty obtaining a single drop of blood from 13% of their patients taking anticoagulation therapy.²⁶ In the present study, several students successfully supplemented autolancing with the use of a tourniquet.

The cost of portable point-of-care INR monitors ranges from $300 to $1,000. Single-use disposable test strip prices vary from $1 to $5 each. Third-party reimbursement to a healthcare provider for performing this procedure is $3 to $10 per test.²⁴

The high percentage of students (79%) who would use INRatio testing in their future practices and the 100% success rate in treating patients suggest that this program effectively trained dental students. These results indicate significantly higher student approval rates than other published surveys of comparable extramural clinical rotation outcomes.^39,40 Students’ survey responses were consistent regarding both positive (dental procedures after INRatio analysis) and negative (difficult blood sampling) clinical outcomes. Seven of 8 students whose patients required more than one blood sample attempt indicated on their surveys that they had difficulty. The main limitation of this research was the small number of clinical patients.

Conclusion

The results indicate that INRatio analysis can be included in dental student training, providing safe, efficient, and successful patient care. Difficulty obtaining blood samples underscores the need for extra training, additional clinical experience, and the use of INR devices requiring smaller blood samples.

References

1. Baglin TP, Keeling DM, Watson HG; British Committee for Standards in Haematology. Guidelines on oral anticoagulation (warfarin): third edition-2005 update. Br J Haematol. 2006;132(3):277-285.

2. Owens CD, Belkin M. Thrombosis and coagulation: operative management of the anticoagulated patient. Surg Clin North Am. 2005;85(6):1179-1189.

3. Salem DN, Daudelin DH, Levine HJ, et al. Antithrombotic therapy in valvular heart disease. Chest. 2001;119(suppl 1):207S-219S.

4. Hirsh J, Dalen JE, Anderson DR, et al. Oral anticoagulants: mechanism of action, clinical effectiveness, and optimal therapeutic range. Chest. 1998;114(suppl 5):445S-469S.

5. Mok CK, Boey J, Wang R, et al. Warfarin versus dipyridamole-aspirin and pentoxifylline-aspirin for the prevention of prosthetic heart valve thromboembolism: a prospective randomized clinical trial. Circulation.1985;72(5):1059-1063.

6. Morimoto Y, Niwa H, Minematsu K. Hemostatic management of tooth extractions in patients on oral antithrombotic therapy. J Oral Maxillofac Surg. 2008;66(1):51-57.

7. Jiménez Y, Poveda R, Gavaldá C, et al. An update on the management of anticoagulated patients programmed for dental extractions and surgery. Med Oral Patol Oral Cir Bucal. 2008;13(3):E176-E179.

8. Al-Mubarak S, Al-Ali N, Abou Rass M, et al. Evaluation of dental extractions, suturing and INR on postoperative bleeding of patients maintained on oral anticoagulant therapy. Br Dent J. 2007;203(7):E15.

9. Pototski M, Amenábar JM. Dental management of patients receiving anticoagulation or antiplatelet treatment. J Oral Sci. 2007;49(4):253-258.

10. Wahl MJ. Dental surgery in anticoagulated patients. Arch Intern Med. 1998;158(15):1610-1616.

11. Souto JC, Oliver A, Zuazu-Jausoro I, et al. Oral surgery in anticoagulated patients without reducing the dose of oral anticoagulant: a prospective randomized study. J Oral Maxillofac Surg. 1996;54(1):27-32.

12. Steinberg MJ, Moores JF III. Use of INR to assess degree of anticoagulation in patients who have dental procedures. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 1995;80(2):175-177.

13. Stern R, Karlis V, Kinney L, et al. Using the international normalized ratio to standardize prothrombin time. J Am Dent Assoc. 1997;128(8):1121-1122.

14. Brennan MT, Hong C, Furney SL, et al. Utility of an international normalized ratio testing device in a hospital-based dental practice. J Am Dent Assoc. 2008;139(6):697-703.

15. Plaza-Costa A, Garcia-Romero P, Poveda-Roda R, et al. A comparative study between INR and the determination of prothrombin time with the Coaguchek^® portable coagulometer in the dental treatment of anticoagulated patients. Med Oral. 2002;7(2):130-135.

16. Scully C, Wolff A. Oral surgery in patients on anticoagulant therapy. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2002;94:57-64.

17. Jeske AH, Suchko GD; ADA Council on Scientific Affairs and Division of Science; Journal of the American Dental Association. Lack of a scientific basis for routine discontinuation of oral anticoagulation therapy before dental treatment. J Am Dent Assoc. 2003;134(11):1492-1497.

18. Salam S, Yusuf H, Milosevic A. Bleeding after dental extractions in patients taking warfarin. Br J Oral Maxillofac Surg. 2007;45(6):463-466.

19. van den Besselaar AM. Accuracy, precision, and quality control for point-of-care testing of oral anticoagulation. J Thromb Thrombolysis. 2001;12(1):35-40.

20. Plesch W, van den Besselaar AM. Validation of the international normalized ratio (INR) in a new point-of-care system designed for home monitoring of anticoagulation therapy. Int J Lab Hematol. 2009;31(1):20-25.

21. Boehlen F, Reber G, de Moerloose P. Agreement of a new whole-blood PT/INR test using capillary samples with plasma INR determinations. Thromb Res. 2005;115(1-2):131-134.

22. Ignjatovic V, Barnes C, Newall P, et al. Point of care monitoring of oral anticoagulant therapy in children: comparison of CoaguChek Plus and Thrombotest methods with venous international normalised ratio. Thromb Haemost. 2004;92(4):734-737.

23. Koerner SD, Fuller RE. Comparison of a portable capillary whole blood coagulation monitor and standard laboratory methods for determining international normalized ratio. Mil Med.1998;163(12):820-825.

24. Yang DT, Robetorye RS, Rodgers GM. Home prothrombin time monitoring: a literature analysis. Am J Hematol. 2004;77(2):177-186.

25. Siebenhofer A, Rakovac I, Kleespies C, et al. Self-management of oral anticoagulation in the elderly: rationale, design, baselines and oral coagulation control after one year of follow-up. A randomized controlled trial. Thromb Haemost. 2007;97(3):408-416.

26. Woods K, Douketis JD, Schnurr T, et al. Patient preferences for capillary vs. venous INR determination in an anticoagulation clinic: a randomized controlled trial. Thromb Res. 2004;114(3):161-165.

27. Linnebur SA, Ellis SL, Astroth JD. Educational practices regarding anticoagulation and dental procedures in U.S. dental schools. J Dent Educ. 2006;71(2):296-303.

28. Yasaka M, Naritomi H, Minematsu K. Ischemic stroke associated with brief cessation of warfarin. Thromb Res. 2006;118(2):290-293.

29. Ogiuchi H, Ando T, Tanaka M, et al. Clinical reports on dental extraction from patients undergoing oral anticoagulant therapy. Bull Tokyo Dent Coll. 1985;26(4):205-212.

30. Patatanian E, Fugate SE. Hemostatic mouthwashes in anticoagulated patients undergoing dental extraction. Ann Pharmacother. 2006;40(12):2205-2210.

31. Ansell J, Hirsh J, Poller L, et al. The pharmacology and management of the vitamin K antagonists: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy. Chest. 2004;126(3 suppl):204S-233S.

32. Wahl MJ. Myths of dental surgery in patients: receiving anticoagulant therapy. J Am Dent Assoc. 2000;131(1):77-81.

33. Blinder D, Manor Y, Martinowitz U, et al. Dental extractions in patients maintained on continued oral anticoagulant: comparison of local hemostatic modalities. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 1999;88(2):137-140.

34. Mulligan R, Weitzel KG. Pretreatment management of the patient receiving anticoagulant drugs. J Am Dent Assoc. 1988;117(3):479-483.

35. Blinder D, Manor Y, Martinowitz U, et al. Dental extractions in patients maintained on oral anticoagulant therapy: comparison of INR value with occurrence of postoperative bleeding. Int J Oral Maxillofac Surg. 2001;30(6):518-521.

36. Carter G, Goss A, Lloyd J, et al. Tranexamic acid mouthwash versus autologous fibrin glue in patients taking warfarin undergoing dental extractions: a randomized prospective clinical study. J Oral Maxillofac Surg. 2003;61(12):1432-1435.

37. Pettinger TK, Owens CT. Use of low-molecular-weight heparin during dental extractions in a Medicaid population. J Manag Care Pharm. 2007;13(1):53-58.

38. Williams VK, Griffiths ABM. Acceptability of CoaguChek S and CoaguChek XS generated international normalised ratios against a laboratory standard in a paediatric setting. Pathology. 2007;39(6):575-579.

39. Thind A, Atchison K, Andersen R. What determines positive student perceptions of extramural clinical rotations? An analysis using 2003 ADEA Senior Survey data. J Dent Educ. 2005;69(3):355-362.

40. Chmar JE, Harlow AH, Weaver RG, et al. Annual ADEA survey of dental school seniors, 2006 graduating class. J Dent Educ. 2007;71(9):1228-1253.

About the Authors

David L. Hall, DDS Associate Professor
Section of Primary Care
The Ohio State University College of Dentistry
Columbus, Ohio

Attending Dentist
Ohio State University Medical Center
Columbus, Ohio

Abdel R. Mohammad, DDS, MS, MPH
Professor of Geriatric Dentistry and Oral Medicine
The Ohio State University College of Dentistry; Director
Geriatric Dentistry and Community Outreach and Engagement Programs
The Ohio State University College of Dentistry
Columbus, Ohio