What Is PT INR Test and Why Is It Important?

What is PT INR test?

The full form of PT is Prothrombin time and the INR denotes Internationalised normalised ratio. PT INR test is basically a test to evaluate how your blood clots and is especially important when patients are on blood-thinning medications (anticoagulant) for e.g. warfarin

What are the requirements before testing for PT INR testing?

There are no special requirements for PT INR testing. The patient is reassured that only a tiny prick to collect venous blood in blue topped vacutainer is the only requirement. The trained phlebotomists and technicians at Aster Labs have all qualifications and training to collect an adequate sample for testing. There are no serious consequences post blood collection.

How is PT/INR test performed or derived?

The traditional manual but labour intensive time tested methods for Prothrombin time utilises mixing of an external tissue factor to convert precursors to thrombin and then add ionised calcium to start clotting so as to evaluate the prothrombin time.

The modern automated coagulometers have replaced manual tests so as to reduce testing subjectivity by removing minor manual errors like pipetting errors.  The automated coagulometers utilise either the electromechanical impedance endpoint detection methods or the photo-optical analysis to detect exact clotting time for the benefit of the patient and help in diagnostic and therapeutic.

INR on the other hand is a calculated value so as to compare Prothrombin time results from different laboratories. INR utilises International sensitivity index (ISI) which is an experimentally derived value that is typically determined by a manufacturer for specific instrument / reagent combinations.

What is the significance of PT/INR testing?

The normal Prothrombin time is in between 11 to 14 seconds and is useful 

1. In diagnosing bleeding and clotting disorders 

2. To evaluate the condition of the liver as a part of liver function tests

3. To plan for surgeries 

INR is a calculated value and is usually between 0.8 to 1.1 and is derived from standardised reagents so that patients can compare INR results done in various laboratories and consultants can utilise these values for the benefit of patients. An abnormal INR is usually because of treatment with oral anticoagulants for patients having stroke to prevent arrhythmias or to prevent deep vein thrombosis or complications like pulmonary embolism. INR is also requested in patients with prosthetic heart valves to avoid the same consequences.

In conclusion PT/INR helps your doctor alter or temper your doses of oral anticoagulants so as to reduce dosages, skip dosages or to institute drugs to reverse the effects of warfarin. We at Aster Labs have stringent quality assurance measures and training sessions imparted to technicians so that patients are given accurate results and help doctors to treat patients in some of the disorders as mentioned.