June 2011
Volume 32, Issue 5

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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


OBJECTIVES: This study aimed to teach dental students to use an INRatio® (HemoSense) device, to apply the results to patients, and to evaluate the outcomes.
DESIGN: This was a retrospective convenience data study that used student surveys.
The research was conducted at The Ohio State University College of Dentistry Geriatric Dental Program in Columbus, Ohio.
PARTICIPANTS: A total of 105 senior dental students participated in an INRatio training program.
The instructions involved the following: 1) a table showing INRatio protocol and dental procedures versus international normalized ratio (INR) guidelines; 2) an online technique training course, 3) a trial INRatio test on another senior dental student; and 4) INRatio for a dental patient.
The clinical outcomes including INR values were a retrospective convenience data study. Instructional outcomes were obtained from student surveys.
RESULTS: A total of 79% of students indicated they would use portable INR testing in their future practices; however, 73% of students had difficulty obtaining an adequate blood sample. All patient surgical procedures were completed successfully without serious complications.
CONCLUSIONS: This study indicates the INRatio analysis can be included in dental student training, providing safe, efficient, and successful patient care. Difficulty obtaining blood samples suggests the need for extra training, additional clinical experience, and INR devices requiring smaller blood samples.

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 4.09,17,18 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 home24,25 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 (http://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.


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).


Studies have shown that the risks of discontinuation of antithrombotic therapy9,28,29 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 4.09,17,18 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) sutures8,33; 2) gelatin packs and cellulose sponges33,34; 3) local anesthetic infiltration with vasopressor16; 4) elimination of inflamed and/or infected granulation tissues6,35; 5) tranexamic and aminocaproic acid rinses30,33,36; 6) fibrin glue33,36; 7) heparin or low-molecular-weight heparin “bridge” therapy31,37; 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.


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.


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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

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