CLIA Survey Findings Regarding the International Normalized Ratio (INR) Calculation

PDF Version of BQA 02-006 (PDF, 5 KB)

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Date: February 14, 2002 DSL-BQA-02-006

To: Laboratories Reporting the INR Result - CLIA 01

From: Sharon Abraham, Supervisor, Clinical Laboratory Unit

cc: Susan Schroeder, Director, Bureau of Quality Assurance

In the past few months CLIA surveyors have reported that some laboratories are not following instructions on the thromboplastin insert for calculating the INR result. Laboratories failing to follow the manufacturer’s instructions have not determined the normal patient mean according to the instructions in the thromboplastin insert.

Please read the thromboplastin insert for your test method. If you have determined a normal patient mean for the current lot of thromboplastin in use, be sure that the correct value has been entered into the system used to calculate the INR. This may be the coagulation analyzer, a laboratory information system, or a manual calculation. Also confirm that the correct International Sensitivity Index (ISI) value for the lot of thromboplastin currently in use has been entered into the system for calculation of the INR.

The laboratory must ensure physicians have not received erroneous INR results. If the laboratory has not been using the correct ISI, the appropriate normal patient mean value, or the INR was incorrectly calculated, the physicians for the affected patients need to be notified of the recalculated INR results. Document all corrective actions.

Surveyors are available to assist you if you have questions about calculation of the INR and the reporting of prothrombin time results. You may contact the Clinical Laboratory Unit at 608-261-0653  or e-mail abrahsa@dhs.state.wi.

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