Why are the test results different for the same drop of blood?

Why are the results of the same drop of blood, measured using three different brands of blood glucose meters, so different? This is a question from a netizen on a certain website. There is also a picture posted together with the question, which shows the results measured by three different blood glucose meters: 13.6mmol/L, 11.8mmol/L, and 9.9mmol/L.

Following closely, there were many comments, and most people thought: The gap between blood glucose meters is too big, and they don’t know which blood glucose meter to trust; the maximum difference and the minimum difference are actually 3 values different. Is it okay to measure blood glucose? Significant.

Reasons why blood sugar levels vary greatly

In response to these questions, first of all, we need to say with certainty: monitoring blood sugar is very meaningful. If controlling diabetes is regarded as a war without gunpowder, then monitoring blood sugar is an essential enemy situation investigation to win the war. Among the "five carriages" recognized around the world for the prevention and treatment of diabetes, monitoring blood sugar is an essential one. So, there is no doubt about this.

So, will there be errors in monitoring blood sugar? Are there any operational errors? This issue should be viewed from four aspects:

First, according to the "National Standard of the People's Republic of China - General Technical Conditions for Blood Glucose Monitoring Systems for Self-Testing of In Vitro Diagnostic Testing Systems", if the measurement result deviation of the blood glucose meter and test strip meets the requirements in the following table, it is considered qualified.

Take the situation at the beginning as an example. If the blood sugar is 13.6, the result is greater than or equal to 5.55mmol/L. Therefore, as long as the plus or minus does not exceed 15%, it will be fine. Taking 13.6 as the base point, the range of plus or minus 15% is between 11.56 and 15.64. As long as Within this scope, everything is allowed by the state. Of course, this difference is too big. Because of this, from a medical perspective, the monitoring results of a blood glucose meter can only be used to judge blood sugar control, but not to diagnose diabetes.

Moreover, if you want to see whether the blood glucose meter is qualified, you cannot use different blood glucose meters to compare, but you should use the blood glucose meter and biochemistry to compare, because almost all blood glucose meters and biochemistry currently have errors.

If the normal blood glucose meter error is exceeded, you can contact the manufacturer for after-sales service.

Second, the same drop of blood needs to be tested with three blood glucose meters, which means that this drop of blood is very small, so it involves that the drop of blood comes from different surface layers, some from the superficial layer, some from the deep layer, and it may be squeezed out got some tissue fluid. Therefore, the results of different blood tests are naturally different. This has nothing to do with blood glucose meters.

Third, it is understandable that if you use different blood glucose meters to measure different fingers, you will get different results. Because the blood sugar test of capillary blood can be interfered by many external environments, such as different times, depth of finger pricking, mood, etc., the blood sugar obtained will definitely be different.

Fourth, we must also prevent deviations caused by incorrect operation, such as blood glucose test strips that have exceeded the expiration date, fingers that have not been disinfected with alcohol, and blood glucose meter codes that are not adjusted to the same as the test strips.

Ways to Reduce Blood Sugar Differences

So, how do you minimize blood sugar differentials? In addition to the possible differences in the blood glucose meter itself, what we can do is try to operate correctly when monitoring blood sugar:

1. Check whether your blood glucose meter needs to be adjusted. If so, adjust the code of the blood glucose meter so that it is the same as the code of the test strips you are currently using. Note that test strips purchased at different times have different codes, so they must be adjusted first. Glucose meter code;

2. Wash your hands and use alcohol to disinfect your blood-drawing fingers;

3. Droop your arms for 30 seconds to allow blood to fully flow to your fingers;

4. Put the blood collection needle into the pen, select the puncture depth according to the thickness of the finger skin, and prick the finger to take an appropriate amount of blood;

5. After the blood glucose meter indicates to take blood, drop the blood on the indicator hole of the blood glucose test paper;

6. Insert the blood glucose test strip into the blood glucose meter. Note that some blood glucose meters require you to insert the test paper into the blood glucose meter first, and then drop blood on the test paper;

7. After a few seconds or more than ten seconds, read the blood glucose value from the blood glucose meter;

8. Record the blood glucose value and monitoring time in the record book.