Why do different BG machines tell you different results

Hi Terryson,
Actual machines most of us use are merely an indication of Blood glucose.
Perhaps the average of your three machines is close to the true reading?

I would do a calibration on the one in the middle of the results table if it is consistent and easy to use and stick with it like a friend, that is if it calibrates ok first.

When my Accuchek Mobile gave a lower reading than two of the nurses machines at the surgery I requested some calibration fluid from Roche and found in both bands checked, my machine was mid range and therefore almost 'spot on' !

But it is a difficult machine for getting the blood droplet right.

What did surprise me was the wide range of acceptable calibration for the instrument according to Roche....It was in the circa +20% or -20% range!!! Therefore, for a true reading of 5mmol/l the meter would be acceptable if it gave a reading of 4 or 6 mmols/l.

One has to work up a relationship with one's meter, as I have done with my Codefree )...it is so easy to get the blood droplet for a good test, the strips are inexpensive and it gives a reading in the same parish as the Accuchek and is very consistent.

Don't get disillusioned, those here that advocate 'eating to meter' and having a low GI diet are right and one just needs a reliable indicator to do that.
atb
Derek

Terryson10 said:

I recently received news about the Insulinx machines having problems with high BG results so i decided to test the same pool of blood from the same site on all three of my machines.
The results were interesting as none of my machines read the same result even though theoretically i would have thought that they would have done.
This has some what confused me a little and now i don't know which machine to believe

Can anybody help me out??




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Meters are not that accurate with current standards. They get worse if one moves onto the proposed standards. From, "Accuracy of Self Monitoring Blood Glucose Systems in a Clinical Setting: Application of New Planned ISO - Standards" (2013):

Results:
Evaluating GM results according to the current ISO criteria, all GMs reached the minimum acceptable system accuracy criteria. Analysing GM results according to the more stringent planned ISO standard criteria, only 8 of 19 GMs reached the minimum acceptable accuracy criteria, i.e. ≥ 95% of the individual glucose results fell within ± 15 mg/dL of the results of the reference value at glucose concentrations < 100 mg /dL and within ± 15% at glucose concentrations ≥ 100 mg/dL. When results obtained in BG ranges < and ≥ 100 mg/dL were separately analysed, readings of 10 and 8 GMs, respectively, fell in the area of acceptable accuracy.

Conclusions:
The study shows that more than half of the tested GMs would fail the proposed tighter ISO criteria. Most GMs reveal similar accuracy in BG measurement when compared at lower and higher BG ranges.

http://www.clin-lab-publications.com/fi ... lacher.pdf

Note: ± 15 mg/dL is more or less 1.0 mmol/L


From, 'System Accuracy Evaluation of 43 Blood Glucose Monitoring Systems for Self-Monitoring of Blood Glucose according to DIN EN ISO 15197' (2012):

Results:
Complete assessment according to the International Organization for Standardization (ISO) standard was performed for 34 out of 43 systems, and 27 (79.4%) meet the requirements of the standard, i.e., ≥95% of their results showed at least the minimum acceptable accuracy. For 9 of the 43 systems, complete accuracy assessment was not performed due to an oxygen sensitivity (manufacturer’s labeling). The bias (according to Bland and Altman) of all 43 evaluated systems ranged from -14.1% to +12.4%.


Conclusions:
From the 34 systems completely assessed, 7 systems did not fulfill the minimal accuracy requirements of the ISO standard. The CE mark apparently does not guarantee that all BG systems provide accuracy according to the standard. Because inaccurate systems bear the risk of false therapeutic decisions, regular and standardized evaluation of BG meters and test strips should be requested in order to ensure adherence to quality standards.

http://www.journalofdst.org/September20 ... CKMANN.pdf


If you stick to one meter, you can at least tell if your BG is going up or down depending on what you eat but, the result is not likely to be an accurate result. I did read one study which stated that out of all their tests, not a single reading was accurate but the average of them was. It is probably not worth anyone's while in developing a very accurate system because your BG varies according to your blood flow and that is changing all the time. It's very much a rough guide to how you are doing.