Manual INR Check

The Manual INR Check module verifies that the correct ISI and Normal Patient Mean PT values are programmed into a coagulation analyzer. When a new reagent lot is placed into service, both of these calibration parameters must be entered into the analyzer's software. An entry error — a transposed digit, a wrong decimal, or a stale value carried over from a previous lot — will cause all subsequent INR results from that analyzer to be systematically wrong, potentially affecting patient safety for those on oral anticoagulant therapy.

This verification works by recalculating the INR for 3–5 patient specimens using the ISI and Normal Patient Mean PT values that should be programmed into the analyzer, then comparing those calculated INR values to the INR values the analyzer actually reported. If the analyzer's programmed parameters are correct, the reported and calculated INR values will agree within rounding tolerance. Any mismatch indicates a programming error that must be corrected before the analyzer is used for patient testing.

When to Use This Module

This check should be performed in the following situations:

• After programming a new reagent lot — Every time a new thromboplastin reagent lot is entered into service and its ISI and Normal Patient Mean PT are programmed into the analyzer, this check confirms that the values were entered correctly.
• After analyzer servicing or software updates — Instrument repairs, firmware upgrades, or any event that could reset analyzer parameters should be followed by this verification to confirm that calibration values were not altered.
• Periodic verification — Some laboratory policies and accreditation programs recommend periodic confirmation that the analyzer's programmed parameters remain correct, particularly for high-volume coagulation analyzers where programming errors may otherwise go undetected.
• Discrepant INR results — When a patient's INR result is inconsistent with their clinical status or recent history, a Manual INR Check can quickly determine whether the discrepancy is caused by incorrect analyzer programming rather than a true change in the patient's anticoagulation status.
• Accreditation requirements — CAP and The Joint Commission require documented verification of INR calibration parameters as part of PT/INR system qualification records.