An invalid blood test result despite a positive PT test can occur due to various reasons. One possibility is that there was an error or issue with the blood sample collection, handling, or processing. It could also be caused by interference from certain medications or substances in your bloodstream. Additionally, technical issues with the testing equipment or methodology could lead to an invalid result. To determine the exact cause, it is recommended to consult with your healthcare provider who can review your specific case and provide further guidance. They may suggest repeating the blood test using proper protocols and precautions to ensure accurate results.