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Meter discrepancies, which one?

Kristin251

Expert
so it’s time for a new meter. My old one was discontinued and I’m getting close to running out of strips by the end of the year.

History. A1C last 4 6 month tests were 5.1 ( average 100 US). According to my meter readings I was always surprised as i thought it would be closer to 4.6 (85)

After TOO MUCH research on meters and reading reviews I decided to just get one that seemed less criticized as other ( of course they were all bashed). I’m going to take a pot of 50 of each strips, use the same blood and see how different they are.

The new meter is running about 15 points higher which would match closer to my A1C. So it appears my old meter has always run about 15 points low.

Question then, do I just take the new meter and assume it’s more accurate?

After typing this out I think I have my answer. Just not used to seeing higher numbers !! I always trusted my old meter and I k ow of the allowed variance but as an insulin user with tight control I’m a bit freaked out to change. But I have no other options. The new one is cuter than the old one. Bonus. Matches my shoes and handbag!
 
Given HbA1C is an average 24 hours a day, 7 days a week, personally, I don't hold much stead on a meter's ability to estimate my HbA1C - I test more often when I know my readings are too high or, more often, too low so the estimate would be hugely skewed by these readings. I rarely test in the middle of the night so my usual fasting readings (apart from one first thing in the morning) are missed and replaced by my daytime readings which are affected by food and exercise.
A CGM like a Libre may be more accurate.

That said, all meters must comply to a standard. I believe (but can't for the life of me find the source of this belief) the standard allows for a variance of 12%. This results in a bigger absolute variation for higher readings:
- if your meter says 5.0mmol/l (90mg/dL) you could be anything from 4.4 to 5.6 (79 to 101)
- if your meter says 15mmol/l (270mg/dL) you could be anything from 13.2 to 16.8 (238 to 302)

So it could be your old meter was usually reading at the lower end of its tolerance and your new one at the upper end. They *should* both be equally accurate.
 
The only way to know if there is a consistent difference is to do as you suggest. Test them side by side on the same drop of blood.

If it is just random variance then you should see them agree sometimes and be higher or lower other times.

If one meter is reading consistently lower than the other then there is some kind of bias.

I don't know if some read slightly high (like car speedometers) or slightly low for a percieved safety margin.

All I can add from my own experience is that I decided to test my new ketone meter but put the BG strip in by mistake. Tested on the same drop of blood and got something like a 5.1 when my usual BG meter was about 5.6. I was thinking I might have overdone the ketones a bit until the penny dropped. I haven't cross checked since (normally have only a very small drop of blood) but you do wonder if some read high and some read low. Consistency is the main thing.
 
Does your doctor/nurse have a meter you can cross check with using the same blood sample? Also, different batches of test strips can give different results.
 
Yes. Most times we cross check mine is low. The A1C says I average 100 and my meter readings are rarely over 100 which is why I believe the new one is more accurate. It’s reading closer to my A1C and it is consistently higher, averaging 13 higher which is spot on to match my A1C. I’ll finish the pot of 50 with each meter and do some analyzing.
It’s hard to know what to trust but it seems the old was always running low.

Good point on safety and running higher meters.
 
See these tables for ISO meter accuracy standards, to which they must all conform. The first table applies to 2013, the second applies from 2016.

http://www.diabetes.co.uk/blood-glucose-meters/blood-glucose-meter-accuracy.html

Some meters are known to read higher than others. The Codefree has plenty of anecdotal evidence on this on this forum, and presumably the Tee2 as, again anecdotally, these 2 meters seem to read the same. The Codefree definitely reads higher than my Accu Chek Mobile.

@Kristin251 It could of course be your A1c that is falsely elevated, like mine seems to be.
Have you considered trying a Libre sensor/CGM? They would save all that finger pricking worry and stress.
 

Always find this an interesting observation on the Codefree. For my last but one HbA1c (the first one for which I had a full 3 months of meter readings) it was spot on, but for the last one my HbA1c was a few points higher than the meter average suggested, so in my case I don’t think the Codefree reads high - unless I’m another with an elevated A1C.
 
Also what we care about is the BG in the blood going around our body, this is higher than the blood from a finger prick, so the meters correct for this.
 

I think with the Codefree the problem can be with the batch numbers. Historically, certain batch numbers were very high, and often varied between tubs. Home Health were involved in all this and made a suggestion it could be the weather conditions/temperature when they were shipped from the manufacturers (in Korea??) to the UK. I used the Codefree for just under 3 years but go so annoyed with the inconsistencies that I stopped and reverted to my Accu-Chek. I haven't used the Codefree since 31st December 2016 so things may have changed in the meantime.
 
I know. Could be the A1C or the meter. No way to know for sure. Shame as an insulin user trying to stay in non diabetic ranges accuracy matters. This is why I eat low carb and small meals allowing me to take small doses and I can only hypo so far right?

With the allowed 20% error if I’m sitting at 100 I could potentially be 80 or 120. Both requiring very different doses and amount if food to eat. Arg. Nothing with D is easy....
 
No it hasn’t changed! I had a whole dodgy batch (ten boxes) reading higher through out Aug/Sept this year. The batch of ten since have been back to where I was in July, except one tub which I opened last week which were high so I put them to one side. I meant to phone them about it. Thanks this has reminded me!
 


Agree, there are inconsistencies. Hadn’t thought of contacting Home Health. Would be interested to hear how you get on @Rachox
 
@Rachox @Goonergal

I had a whole batch of 10 boxes replaced for free, but in return they wanted me to do some comparison tests between the bad ones and some from other batches that they sent me, and at the same time Mr. Home Health also did some comparisons on himself. (He isn't diabetic!!!!!) He said he had no diabetics working in the office with him so had to be the guinea pig.. He was very approachable and very concerned about quality. He also contacted the manufacturers in Korea and asked them to do proper standard testing on them comparing results with other brands of meters.
 
Just looked back at the graphs in one of my blood sugar apps, it was infact July/Aug (not Aug/Sept as I said above) that I had the dodgy batch, you can clearly see my gradual decline in average sugars which then showed a rise before going down again during that time Maybe I should suggest I send him my graph?
 
Regarding SD Codefree - there is a comparative assessment of SD Codefree, which was published in Sep 2017 in BMC Research Notes.

The researchers in Ghana took 100 diabetic patients and 50 non diabetic patients and simultaneously measured their blood glucose concentration using SD Codefree (finger prick blood) and reference auto analyzer BT-3000 (venous blood). The conclusion was that SD Codefree is fairly accurate in the whole operational range. The complete article can be found here.

Looking at the article's results and based on my current one week experience with SD Codefree, it looks that the measured values are slightly and consistently elevated but it should be possible to "calibrate" it for myself - if I had some reference values - how to get them? The trends - highs/lows, increases/decreases - are probably tracked accurately, I don't get too many outliers.

Based what I have read here and on other forums, SD Biosensor had in past for some time problems with QA and some batches of test strips had issues, but it looks that they have finally tuned their manufacturing process and results are overall consistent.

The price of measurement strips is really good.

What is your current experience?
 
Very interesting @Bluetit1802 and @Rachox

I got the Caresens Dual this week - to test for ketones rather than BG, but it did come with 10 free strips so I’m doing some limited comparisons. Tuesday evening post dinner Codefree was 5.3 and Caresens was 5.1 so no difference.

This morning Codefree was 5.3 and Caresens was 6.2.
 

Thank you. That is very informative.
 
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