Bleeding time is a clinical laboratory test performed to evaluate platelet function. It involves the creation of a standardized incision and timing the cessation of bleeding. The historical indications were the pre-operative assessment of patients taking aspirin or NSAIDs and screening for von-Willebrand disease. Unfortunately, it is insensitive and lacks reproducibility. Platelet function assay (i.e PFA 100) has largely replaced bleeding time. Despite standardization of methods, the sensitivity and specificity of the bleeding time for platelet-mediated coagulopathy is low.
Many hospitals and health systems have removed the test without any demonstrated harm. In most cases, a thorough history and physical is the only workup needed for the pre-operative assessment of bleeding risk. When the clinical effectiveness of platelet aggregation is desired, a modern platelet function assay can provide the necessary information. This is being increasingly utilized in intracranial hemorrhage on various antiplatelet agents prior to pooled platelet transfusion.
While measuring the bleeding time requires trained personnel, no gross specimen collection is necessary. Modern alternative platelet function analyzers require a small aliquot of peripheral blood. Technicians utilize standardized instruments to perform and interpret the test.
This test is performed via two primary methods based on the length and location of the incision.
The IVY method is the most common. The patient’s arm is positioned at the level of the heart, and a blood pressure cuff inflated to 40 mmHg. After cleansing with alcohol, a standardized device is utilized to make a 10mm long and 1mm deep incision on the volar forearm. Using a timer the blood is blotted twice a minute. The time stops when there is no further bleeding after blotting.
The Duke method involves a stab incision in the patient’s cleaned finger or earlobe with a lancet. Otherwise, the methodology is the same.
The IVY method is more accurate but has an increased scarring risk. The Duke method is less accurate and carries a higher hematoma rate.
Either method carries the risks of infection and bleeding. In addition, the discomfort is not insignificant. Different normal ranges exist for each method further confounding the interpretation of results by lay clinicians.
The measurement of bleeding time is mostly of historical value in the screening of qualitative platelet abnormalities. It was used to screen for bleeding disorders and quantify platelet function in patients taking aspirin or non-steroidal anti-inflammatory medications. The American College of Clinical Pathologists position statement identifies a carefully conducted clinical history that includes family and previous dental, obstetric, surgical, traumatic injury, transfusion, and drug histories as the best predictor of bleeding risk. As most hospitals and laboratories have removed this exam from their offerings, it has fallen out of regular use. Most current uses are likely grounded in physician preference rather than clinical research.
Normal bleeding time:
Times greater than 5 minutes in the Duke method and 10 minutes in the IVY method are concerning for coagulopathy. Abnormalities would require further evaluation with a focus on the coagulation pathway of interest.
Anything that alters platelet function can interfere with the bleeding time. Some examples include aspirin, thrombocytopenia, and uremia. Additional factors include the test procedure and subjective observation by the performing technician. As with all subjective tests, this one is at risk of human error.
Both methods carry a risk of local scarring due to the incision, but this is worse in the IVY technique. Local pain, infection, hematoma, and aberrant results are other potential complications. The risk of misdiagnosis due to the poor sensitivity and specificity of bleeding time is an often unaccounted complication.
The University of Utah Health Sciences Center undertook a retrospective review of bleeding complications in kidney biopsy five months before and after discontinuation of the bleeding time test. There were no statistically significant differences in post-procedural complications, DDAVP administration, or transfusions between the two groups. Additionally, the clinicians surveyed did not alter their workup and treatment of these patients. This data supports the removal of bleeding time from the workup of presurgical patients. Although the test is safe, its use continues to come under scrutiny due to low sensitivity and specificity. If your doctor requests this test, inquire whether a platelet function assay would be more appropriate. Consultation with a hematologist is the proper recommendation if the clinical picture is unclear.
Clinicians have sought a global test to assess the adequacy of primary hemostasis. While the bleeding time seems the logical fit, it has proven a poor predictor of clinical bleeding. Its diagnostic sensitivity and specificity are also disappointingly low. “The bleeding time is affected by a large number of diseases, drugs, physiologic factors, test conditions, and therapeutic actions, not all of them platelet-related.” In May 2011 a double-blinded randomized control trial demonstrated that several points of care platelet function analyzers were equal or superior to bleeding time in the diagnosis of aspirin and clopidogrel mediated coagulopathy. With the adoption of modern platelet function analyzers, this test has largely been abandoned.