Harr Hematology Practice Test 2026 - Free Hematology Practice Questions and Study Guide

In the context of hematology tests, especially those requiring accurate results such as Prothrombin Time (PT) and Activated Partial Thromboplastin Time (APTT), the proper volume of blood in the blue-top tube (which contains sodium citrate) is crucial. The tube is designed to maintain a specific blood-to-anticoagulant ratio, which is typically 9:1. If the correct volume of blood is not reached, as in this scenario where only 3.0 mL of blood was submitted in a 4.5-mL tube, the anticoagulation properties of the sample may be compromised.

When a sample is not filled to the required volume, it may result in an incorrect anticoagulant-to-blood ratio, leading to aberrant test results that cannot be relied upon for clinical decision-making. Additionally, this compromised ratio can affect the accuracy of both the PT and APTT tests, potentially leading to misinterpretation of a patient's coagulation status.

Consequently, the best course of action for the technologist is to reject the sample and request a new sample, ensuring accurate and reliable results for the patient. This approach prioritizes patient safety and the integrity of the testing process.