A retrospective review of clinical international normalized ratio results and their implications.

Background: Warfarin is a key element in therapy for atrial fibrillation, deep venous thrombosis (DVT), stroke (cerebrovascular accident) and cardiac valve replacement. Often, patients' warfarin blood levels are not tightly controlled with regard to accepted therapeutic ranges, by virtue of the drug's unpredictable nature.

Methods: The authors searched 16,017 active clinical charts for active patients of record from the three campuses of the School of Dentistry, Marquette University (MU), Milwaukee, for the years 2009 and 2010. Dental records of 315 patients contained entries including "INR," the abbreviation for the term "international normalized ratio." Only 247 of those records contained an indication of whether the patient's INR values were within therapeutic range. The authors found that 1.96 percent of the total MU dental clinic patient population had a history of warfarin use.

Results: When the authors compared the INR values for patients with diagnoses of atrial fibrillation, DVT, stroke and cardiac valve replacement, they found that INR values for 107 of the 247 patients (43.3 percent) were not within therapeutic range for the respective diagnoses. For example, only 50 percent of the patients being treated for atrial fibrillation presented themselves for surgical dental treatment while their INR values were in tight control.

Conclusion: The INR values for a significant number of dental patients are not within the therapeutic range for their medical conditions. These patients need to seek follow-up care from their medical care providers.

Clinical Implications: Screening for INR in the dental office-especially before invasive dental treatment such as periodontal surgery, tooth extraction and dental implant placement-can help prevent postoperative complications. It also can aid the clinician in evaluating whether a patient's INR is within therapeutic range and, subsequently, whether the patient's physician needs to adjust the warfarin dosage.