Testing international normalized ratio (INR) before surgery is primarily indicated in patients with conditions or medications that may significantly alter coagulation and increase the risk of perioperative bleeding or thrombosis. Current evidence does not support routine INR screening in all surgical patients; instead, testing should be targeted toward individuals with identifiable clinical risk factors (1). One of the most important indications is chronic anticoagulant therapy, particularly warfarin use. Patients taking warfarin for atrial fibrillation, venous thromboembolism, or hypercoagulable disorders require INR testing before surgery to determine whether anticoagulation has been adequately reversed and whether perioperative bridging therapy is needed (1). The INR result directly influences surgical timing and helps guide administration of vitamin K, prothrombin complex concentrate, or fresh frozen plasma when urgent correction is necessary. 

Prosthetic heart valves are a particularly important indication for INR testing before surgery. Individuals with mechanical mitral valves, older-generation aortic mechanical valves, or multiple prosthetic valves are maintained on long-term warfarin because of their high risk for valve thrombosis and systemic embolization (1). In these patients, perioperative management is complex because interruption of anticoagulation increases thromboembolic risk, whereas continuation increases surgical bleeding risk. INR assessment helps determine whether anticoagulation has reached a safe level for surgery and whether bridging anticoagulation with low-molecular-weight heparin or intravenous unfractionated heparin is appropriate. Patients with bioprosthetic valves generally require less aggressive long-term anticoagulation, but INR testing may still be indicated early after valve implantation or when other thrombotic risk factors coexist. 

Another major indication for INR testing is known or suspected liver disease. Because the liver synthesizes most coagulation factors, hepatic dysfunction can prolong clotting time and predispose patients to perioperative bleeding (2). Patients with cirrhosis, chronic hepatitis, alcoholic liver disease, or obstructive jaundice frequently demonstrate impaired coagulation and may require perioperative correction strategies depending on the severity of INR elevation and the invasiveness of the planned procedure. Similarly, patients with malnutrition, prolonged broad-spectrum antibiotic use, or vitamin K deficiency may develop coagulation abnormalities significant enough to affect surgical planning. 

A detailed bleeding history is critical to informing the decision to perform INR testing before surgery. Patients with prior postoperative hemorrhage, excessive bleeding after dental extraction, spontaneous bruising, recurrent epistaxis, or a family history of inherited bleeding disorders may require coagulation evaluation before surgery (2). Although INR alone does not detect all hemostatic abnormalities, an elevated result may identify acquired coagulation defects requiring further investigation. In contrast, routine INR testing in asymptomatic patients without anticoagulant use or liver disease has poor predictive value for perioperative bleeding complications and often leads to unnecessary delays or additional testing (3). 

INR assessment is particularly important before procedures in which even minor bleeding can produce catastrophic consequences. Neurosurgery, spinal surgery, major vascular operations, cardiac surgery, and certain ophthalmologic procedures typically require careful coagulation assessment because confined-space bleeding may result in neurovascular injury, airway compromise, or vision loss. Emergency surgery also frequently necessitates rapid INR testing, especially in elderly patients whose medication histories may be incomplete. 

In summary, rather than being performed routinely, INR testing should be performed before surgery when there are clear indications based on the patient’s clinical status. Careful assessment is especially important in patients receiving warfarin, those with mechanical heart valves or liver disease, and individuals with a significant bleeding history, as INR results may directly influence perioperative management and surgical timing. A selective, risk-based approach allows clinicians to reduce bleeding and thromboembolic complications while avoiding unnecessary testing in low-risk patients. 

References 

1. Douketis JD, Spyropoulos AC, Murad MH, et al. Perioperative Management of Antithrombotic Therapy: An American College of Chest Physicians Clinical Practice Guideline. Chest. 2022;162(5):e207-e243. doi:10.1016/j.chest.2022.07.025 
2. Northup PG, Caldwell SH. Coagulation in liver disease: a guide for the clinician. Clin Gastroenterol Hepatol. 2013;11(9):1064-1074. doi:10.1016/j.cgh.2013.02.026 
3. Chee YL, Crawford JC, Watson HG, Greaves M. Guidelines on the assessment of bleeding risk prior to surgery or invasive procedures. Br J Haematol. 2008;140(5):496-504. doi:10.1111/j.1365-2141.2007.06968.x