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Frequently asked questions

Find answers to your questions about point-of-care testing, patient self-testing, and CoaguChek®.

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Point-of-care (POC) testing

In general, measuring coagulation values is done with biological materials, which can vary naturally in individual patients. In the case of anticoagulation with vitamin K antagonists (VKAs), changes in the activity of the coagulation factors occur, which can also vary between different patients.

In addition to these immutable “natural” differences, external factors can contribute to measurement value deviations. This can result in differences between measurement values from different labs and results obtained using the CoaguChek® system.

Here are just a few of the contributing factors:

  • Varying sensitivities of the reagents used
  • Varying procedures during the pre-analytics
  • Influences of the calibration (determination and consideration of the deviation of a reagent/measuring device from a reference)

Note: Quick values measured with different reagents cannot be compared with one another because of the lack of standardization. Therefore, most professional associations now recommend the use of the INR value.

Pre-analytics include the various process steps that are taken before, during, and after the sample-taking for measurements using the CoaguChek® Pro II (XS Pro) system in a clinic or lab. From experience, these steps contain a number of sources of error that can influence the measurement results.

If for some reason you are concerned about the accuracy of your CoaguChek® results, you can validate the results accuracy using one of the following methods:

1. Run a Quality Control test using the CoaguChek® control solution to check if the result falls within the acceptable range. Contact the CoaguChek® Roche Care Center for support (1-877-426-2482), Monday to Friday between 8 a.m. and 5 p.m. (EST).

2. Run a correlation (comparison) test using your CoaguChek® meter against a laboratory prothrombin time (PT/INR) test.

  1. Try to select a laboratory that uses the thromboplastin reagent Dade® Innovin® for their prothrombin time (PT/INR) test.
  2. Bring a doctor’s prescription for a PT/INR test (for health insurance coverage).
  3. Bring your CoaguChek® meter, lancing device and test strips with you.
  4. The blood draw for the lab test and your CoaguChek® INR test should be done at the same time, one after the other, to ensure that the warfarin level in your body is the same.
    • Please run your CoaguChek® test as usual, using a fingerstick sample of blood. (Do NOT use the blood from the lab test tube because it contains citrate, which alters the CoaguChek® test).
  5. Record your CoaguChek® test result.
  6. Wait for the laboratory INR test result.
    • You will need to ask that the lab INR result be sent to both you and your doctor as soon as possible, otherwise there may be an unnecessary delay.

  • Test strips must be stored in the original vial, tightly capped, at room temperature 2-30 °C (36-86 °F).
  • Wash the patients hands with soap and water prior to pricking the finger.
  • If you choose to clean with alcohol, allow area to dry completely.
  • Sample blood is taken the usual way from a fingerstick, the first drop, and applied within 15 seconds to the test strip.
  • Applied blood should NOT be taken from a test tube or from a butterfly needle after other tubes are filled.
  • Use the test strip within 10 minutes of removal from vial.
  • Do not touch the test strip or add more blood to it during the test.

  • Blood should be drawn from a needle that is ideally 21-gauge in diameter.
  • Minimum needle diameter is 23-gauge.
  • If multiple lab tests are needed, the INR sample should be filled first (test tube has a light-blue cap).
  • Test tube sample is stored in correct temperature conditions and length of time prior to prothrombin time analysis.
  • Test tube undergoes minimal shaking or bumping prior to analysis.
  • Ideally laboratory uses the thromboplastin reagent Dade® Innovin® for prothrombin time tests.

Use the following table for comparison tests involving your CoaguChek® meter

If my CoaguChek® result is: And the difference between my
CoaguChek® and the lab result is:
My CoaguChek® is:
≤ 2.0 INR < 0.5 INR difference Good
≤ 2.0 INR ≥ 0.5 INR difference Need more investigation
> 2.0 INR ≤ 30% difference Good
> 2.0 INR > 30% difference Needs more investigation

CoaguChek INR - lab INR

smallest INR value
 x 100
% difference (+ or -)

Patient self-testing

We encourage all healthcare professionals to become familiar with the CoaguChek® INRange/XS. Once familiar with these systems, you will be able to show your patients how to use them confidently.

We also invite you to watch the series of training videos available for each device.

How to use CoaguChek®

CoaguChek® resources for patients

CoaguChek® systems

At least twice per month, but preferably once per week. This has proven to increase time in therapeutic range (TTR) by enabling faster reactions to variations in INR due to exercise and diet. It also increases patient compliance and engagement.1–3

More about patient self-testing

TTR is the percentage of time that your patient’s INR values fell within the upper and lower target value set by you.

No, calibration is performed automatically upon inserting the code key from the strip vial.

NOTE: Important to keep the code key and not discard it when opening the strip vial. If you use a new test strip lot and have not inserted the corresponding code chip yet, you must do so at latest after inserting the test strip. Otherwise, you cannot perform a test. The meter displays the number of the code chip belonging to the new test strip lot. With every change of test strips lot number, dispose of the old code chip with your household waste and slide the new code chip into the slot on the side of the meter.

Due to diverse measurement standards used by labs, small variations should be expected. If the variation is of therapeutic significance, please contact the CoaguChek® Roche Care Centre toll-free at 1-877-426-2482 Monday to Friday between 8 a.m. and 5 p.m. (EST).

Polyglobulism: Hematocrit outside the standard range (25%–55%)

Lupus anticoagulant: INR abnormally high. The presence of anti-phospholipid antibodies (APAs) such as lupus antibodies (LA) can potentially lead to prolonged clotting times (i.e., elevated INR values). A comparison to an APA-insensitive laboratory method is recommended if the presence of APAs is known or suspected.

For further details on CoaguChek® systems interferences and limitations, please refer to the Limitations-interference section of the CoaguChek® strips package inserts.

The open vial stability is 10 minutes maximum. Keeping the strip out of the vial for too long, especially in high humidity or temperature, would be detected by the onboard integrity system and result in an error message. No international normalized ratio (INR) would be displayed if the strips are found to be defective by the integrated quality control of the CoaguChek® system.

If the incorrect code chip is in the machine, you cannot perform a test. The code chip provides the meter with important information which it needs to perform the coagulation test. The chip contains information about the test method, the lot number, and the expiry date.

The meter is ready to use once the code chip has been inserted. If you use a new test strip lot and have not inserted the corresponding code chip yet, you must do so at latest after inserting the test strip. Otherwise, you cannot perform a test. The meter displays the number of the code chip belonging to the new test strip lot.

In the measuring channel, a chemical called resazurin is incorporated. Resazurin is sensitive to ambient factors like light, humidity, and temperature, leading to a reaction process where resazurin is converted into resorufin. The concentration of resorufin is measured electrochemically, and the result is a direct measure of strip alteration.

The fill of the capillary is detected by a current flow between two electrodes on the test strip. If the capillary is not completely filled, an error message (error number 5) will appear on the display.

No. Apply the blood drop to the test strip within 15 seconds after lancing your finger. Applying blood after this period of time could falsify the result as the coagulation process could already have begun. If it takes longer to form a good drop of blood, lance a different finger before doing another test.

CoaguChek® INRange: An error message (error number M-44) will appear on the screen.

CoaguChek® XS: An error message (error number 4) will appear on the screen.

CoaguChek® XS Pro, Pro II: An error message will appear on the screen.

The user can erase the entire memory. A user cannot, however, erase individual results.

The meter has a built-in internal quality control so liquid controls are not needed.

No. The CoaguChek® Pro II system is a much more suitable solution in a professional or POC setting due to the data management capabilities created for professionals:

  • Positive strip lot identification
  • The ability to input patient and operator ID to facilitate record keeping
  • Touchscreen
  • A search function for patient data in the memory

The CoaguChek® Pro II system is the ideal choice for you when accuracy and ease of use need to be combined with data management.

More about POC testing