A coagulation specimen for prothrombin time assay that is unopened and stored at 18-24°C must be tested after collection within a MAXIMUM of:

For a coagulation specimen specifically for prothrombin time (PT) assay, it is crucial to perform the test within a certain timeframe to ensure the accuracy and reliability of the results. When the specimen is unopened and stored at a temperature range of 18-24°C, it is acceptable to test it within a maximum of 24 hours after collection. This time frame helps to preserve the integrity of the specimen and ensures that factors involved in the coagulation process do not decay or become altered, which could impact the results.

Testing beyond this timeframe could lead to inaccuracies in the coagulation parameters due to factors such as the degradation of clotting factors, which may not provide a true assessment of the patient's coagulation status. Therefore, maintaining the specimen within the specified time limit is essential for achieving valid and clinically relevant results.