Accuracy of BG meters

Is it possible for a meter to start giving inaccurate readings? Hairy's readings the last few days have mostly been sky high regardless of when I take the reading. Tonight I tested on myself and it read 288. I am not diabetic. Granted it was at the end of the day but whenever I have been tested with routine blood work it is usually between 90-100. I plan on testing it on myself again in the morning but I'm really suspicious of the accuracy of the readings. Hairy has made dramatic improvement in his symptoms and is negative in urine testing, so I am just having a hard time believing that his BG would be in the 500 to 600+ range being on insulin and showing no symptoms while he was in the 400 range when he was having symptoms and not on insulin. It doesn't seem likely that he is continuously bouncing and that even if he were it would be driving his BG up higher that it was without insulin. Any thoughts?

 

There can be bad batches of test strips.
The test strips may degrade if opened and unused for a while.
Sometimes, the strips may be contaminated if the hands aren't clean.
The meter may be defective.

And Sienne just mentioned it is possible a meter doesn't reset for a new test if they are close together in time here

 

If you tested at 288, then either the strip was bad or the meter is. I'd probably go with the meter being bad if you suspect that Hairy's numbers are false as well.

When you said "negative in urine testing", that's urine glucose as opposed to urine ketones, correct?
That would indicate that hours earlier (not sure how many hours) he didn't have sugar spilling over into his urine, so his BG would have been under the "renal threshold" at that time. I don't know if there's a precise value associated with the renal threshold, as I've seen numbers ranging from 220 to 250 mentioned as far as where that "line" is.

Probably the best way to check the meter would be to run a side by side test with the vet's meter and see if it's within allowable variance for meters in general.

 

Urine testing shows if the glucose spilled into urine anytime since the last void. So if he urinated at 10pm, and he had urinated previously at 2pm, it means if didn't go over then the renal threshold between 2pm and 10m.

 

Thanks for the explanation. :smile:
OK, then that would indicate that Hairy's numbers aren't always high, right? Doesn't mean they are always low either, but at least this would mean there are low numbers in there someplace. Either the meter/strips are an issue, or Nancy just hasn't been able to catch the low numbers when they happen. And if that's the case, assuming there are lows that aren't being captured, then at least some of the "highs" could be due to bouncing off those lows. If Hairy is testing negative for urine glucose, then at some point(s) in time, he's probably running below 200ish?

 

She also did not state which meter she is getting these readings from. Remember she is using two - alpha and relion and she previously complained about the relion and was given lots of information and suggestions then. ie - bad meter, bad strips, contact manufacturing for replacement, etc. and each suggestion was met with negative response - stating that relion is crap and alpha is better.

Don't think anyone tested themselves with an alpha - so no way to know how that reads human blood.

If she tested on the same relion meter/strips she previously complained about - well.....

 

Well, we dont know when she is checking urine compared to the blood tests. If she checked his urine in for sugar the AM and had high BG readings in the PM, that doesnt tell us anything. Need to check both at the same time
I would check for sugar everytime he urinates for 24 hours and if the high readings continue when checking BG (over 300) during that time also, I would say the meter, strips are bad. But I would also get a fresh box of urinalysis strips to make sure the urine strips are okay too. I never had any bad ones, but I suppose you could get defective ones. Or they could be old, I know they should be used within 30 days after opening.

Nancy, when are you checking the urine? Maybe you could add that to your SS?

 

I talked to my vet today and will take Hairy in tomorrow morning and we will test him with both my AT meter and the vet's.

I have used the Relion meter on Hairy for the last 2 days and reading have been about 35% lower than with the AlphaTrak. I never had a problem (that I know of) with the accuracy/consistency of the readings with the Relion. The reasons I don't like that meter is because it requires more blood and is very slow in displaying any reading with an error message for not enough blood or the BG reading.

I don't really know what the urine tests indicate. They are also made by Relion and they are color coded. I've tested Hairy's uring 4-5 times with them but haven't really tracked when vis a vis his meter tests. Each time they have remained the same beige color as is on the tip of the strip and the instructions indicate that means his urine is negative.

I tested myself with both meters this morning. The Relion was 108 and the AlphaTrak was 357. That is like a 350% increase!

Since I don't test Hairy continuously throughout the day, yes, it is certainly possible that I haven't caught his nadir. But why would he bounce higher than his BG was before he was even on insulin? I understand about the pancreas thinking it needs to get him back to the levels to which he had been accustom, but I have had midcycle readings that were 150-200+ higher than any of his reading before ever being on insulin.

 

Nancy,
There's no way to logically explain the "why so high" nature of bounces. Once the process starts, the sky is the limit I would expect, depending on how severely the liver/pancreas react to a low.

I "watched" a kitty in Lantus TR this morning, who had some insane numbers.

Look at this spreadsheet over the past few days.
https://docs.google.com/spreadsheet/ccc?key=0AjBJGaZt2NrJdHBldUc1dHBaZUpkOEhka1ZVbF9WZXc&output=html
You can see a small bounce yesterday, as Corduroy (on a measly dose of .1u) started the day at 110. Four hours later, he was at 99, which is very flat, and just what you want when you are really close to being off of insulin. This kitty hadn't seen a 200 for days. At some time after +4, the suspicion is that he dropped lower, at least low enough to trigger a bounce. By +10 he was reading 251. He got another .1u dose last night, went up to 271, then the insulin started working to push down his numbers.

This morning he was back down to 116 and got a tiny dose of .1u again. This morning, at +2, he was reading in the low 20s! After lots of carbing him up to get him up to safe numbers, he was around 150 by nadir time. Looked great. Just after that, the "bounce" started showing up on the meter.
Because he dropped so low, the advice was "no more insulin for Corduroy". Tonight, two hours after he would have gotten his PM shot, his BG was 392. All of that is "bounce".

This kitty was just about "done" with insulin, and had been on .1u for several days. He hadn't bounced for a while. But yesterday, an "unseen low" looks to have caused a small short-lived bounce. Today, mere drops of insulin caused him to come within minutes of a trip to the emergency room. His liver freaked out, and good thing it did.

But my point here is that there doesn't seem to be any clear logic to "why today, and why so high?" It just happened. His BG went low enough to possibly cause a seizure if he was in the 20s. It didn't happen, thankfully, but a 392? Corduroy hadn't seen a number that high, or even close to that high, in three weeks.
Brigitte thought, and so did some of us, that maybe her meter was screwy, possibly a battery going bad. She even went out today and got a back-up meter to be sure it wasn't a meter problem. She got similar results after that with both meters. So it looks like her numbers are accurate.

Bounces are just confusing and difficult to deal with, because although the process makes logical sense, the numbers can drive you crazy.

When you bring Hairy in tomorrow and talk to the vet, ask him what is up with that? I know that AT's are "pet specific" but can you ask him to explain what is it that is so different that it would cause the reading to be over three times as high with human blood vs. cat blood? I don't know off hand of anyone who has tested themselves with an AT. I know that many (maybe most) of us have double checked our human meters on ourselves when we see a BG number that seems like it must not be right. I did a couple times when Bob's numbers were wonky. But 108 to 357 is just crazy. :shock:

 

I did ask him today and he thinks there may well be a problem with the meter. That's why we are doing the comparison in the morning of AT to AT on Hairy. He said the ATs will read higher (and more accurately) for cats and humans that human meters, but not anywhere near that much. He says the deltas he has seen are more like 20-30%.

 

Okay, I think you are just testing for ketones, not glucose too, if your sticks just have the color code that is a beige color.
Glucose/ketone tests (Ketodiastix) have 2 colors to check, the glucose is blue (neg) and goes brown (high), and ketones are beige (neg) that can up to maroon (high). You seem to have just the ketone test (Ketostix) .

So all the discussion earlier about comparing it to your BG is n/a.

 

re: the "more accurately" comment by your vet:

Its the difference between reading temperature in Fahrenheit vs Celsius. For example, freezing is 32 degrees Fahrenheit vs 0 degrees Celsius. So long as you have the reference scale for the measurement tool you are using, you do get accurate results, within the limits set by the FDA for meters sold in the US

From a recent article at Medscape (site is free, requires registration), a medical news aggregator:
"..current accuracy standards used by the FDA for clearance — 95% of all measurements must be within 20% of reference values at or above 75 mg/dL and within 15 mg/dL below 75 mg/dL — with errors often being overestimations in the low glucose range." The article was discussing setting up a surveillance program for glucometers

 

Right, but 50% - 350% is not within anybody's acceptable limits.

I'm glad now I didn't test Hairy anymore than I did, since now if appears all of those results could be suspect.

Took him to the vet and we tested him simultaneously on 3 meters: My AlphaTrak2, 572; vet's AlphaTrak, 439, my Relion Confirm, 396.

He also is doing a lab blood test for glucose which he says will be the most accurate result, but won't know what that is until later today.

Guess I will have to start using the Relion as the primary meter after all. Fortunately Hairy is getting slightly more tolerant of the testing and I've become more practiced at how much extra blood the Relion needs so not get the dreaded 7 second delayed E-7 error as often.

 

That's the difference in numbers that seems "normal" here (between his AT and your Relion). We usually expect the AT to read 30 points higher - more in higher range BGs and less in low range BGs. The 30 point difference is built into our protocols and reflected in our advice, which is why we ask people to add "Alpha Track" to their sig. The only time it really matters is in the lower numbers when when hypos or dose reductions are an issue.

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I agree to the extent that if all the high readings were in fact errors in the meter, they would cause people to mistakenly believe that dose increases needed to be made either too quickly or too much at a time. If a nadir of 240 were really a 45, nobody would have advised you to reduce on a 240.

 

We know the human glucometers read on a different scale; this does not make them wrong, nor inaccurate.

They tend to be about 30-40% lower from pet-specific meters.

Specifically, your Confirm vs your AlphaTrac is 396/473 = 69%, ie 31% lower.

This is not a problem. It is reading correctly for the type of meter. The reference numbers you have seen posted indicate the ranges for the different types of meters and for mg/dL vs mmol/L.

Here's the FDA page where you can look up any meter you want and read the technical specifications for any meter you want to research.

 

I'm not sure where you got the 473 number from, but my issue is not the delta between my Relion meter and my vet's AlphaTrac meter, it is the difference between my vet's AlphaTrak meter and my AlphaTrak meter. There shouldn't be any difference, let alone a difference of 133. The number on my AlphaTrac was 572 and my vet's was 439.

 

The difference between the 2 AlphaTracs may the other 5% of the time the FDA allows.

The most important measurement range is when the cat is low. High is high and you take action to reduce the glucose, whether its in the 300s, 400,s or higher, it does not matter what the specific number is, it is too high.

Low, though, can kill quickly. That's why if the glucose is less than 50 mg/dL on a human meter, or less than 80 mg/dL on a pet-specific meter, we take action to keep the glucose from going lower. It could be as much as 15 mg/dL lower as what it is reading.

 

I think we are on two different tracts here. My issue is with the accuracy of the meter that I have been using all along for Hairy's tests. Whether it is wrong by 50% or 350% at any given time, it is wrong. And because of that, whatever it reads, it could be significantly higher or lower for any given reading. The bottom line is that I am trying to regulate Hairy's blood glucose, and it is hard enough to do that under the best of circumstances, and impossible when you use a meter that gives wildly false readings. I understand your celcius and fahrenheit analogy, but it just isn't applicable here. The issue is that the readings are widely different when comparing 2 meters using the same scale, not different ones.

And even when there is a significant variation in degrees of high, it does make a difference as an indication of whether his dosage is appropriate to his BG measurement. Lots of people her have told me about bounces and that I should decrease/increase/not change his dosage based on those high numbers that may have all been faulty with not relative degree of consistency between them.

 

Update: Got a call from my vet's office. The blood test matched their AlphaTrak reading. I called Abbot Animal Services (manufacturer) and so far am getting a runaround. Customer service wants me to deal with tech support and tech support is a voice mail message. So for now at least I will use the Relion on the primary and just assume it to read about 15% lower than an accurate AlphaTrak would.

Update 2: Abbott called me back. Went through several possibilities (miscoding, getting blood on both sides of the strip, blood clotting too quickly, contaminates, etc.) but none seemed to be the case. He had me do a test using the control solution which returned a value in the acceptable range. So basically, nobody knows why the reading are so far off. They are sending me a new meter which I will test against the faulty one. In the mean time, I'll use the Relion.

 

Yay! I'm so glad to hear that things are going better with the testing. I've been wondering about you two.

That's great that they're giving you a new meter. Do you know when you'll be getting it? I'd be interested/curious to see a side-by-side comparison with the old Alpha-Trak vs. the new one.

 

Should have been here by the end of last week but haven't received it yet. Will give it a couple more days and then call them again.

 

These numbers are just nuts. I got the replacement AlphaTrak meter and have done 3 comparison tests:

1. Tested them on myself:
original AlphaTrak: 186
replacement AlphaTrak: 212
Relion: 118

The highest reading on blood tests done by a lab for my BG was 101, so all of those numbers are suspiciously high. Tests were done first thing in the morning before eating or drinking anything.

2. Tested on Hairy about 3 1/2 hours after eating and shot:
original AlphaTrak: 530
replacement AlphaTrak: 486
Relion: 572

This is totally nuts. The reading on the human meter was the highest when you would expect it to be the lowest.

3. Tested on Hairy at vet's office about 2 hours after eating and 1 hour after shot:
original AlphaTrak: 481
replacement AlphaTrak: 417
vet's AlphaTrak: 394

So based on that comparison, vet feels the difference between his meter (which was previously confirmed to be accurate compared to actual blood test) and my replacement AlphaTrak is within an acceptable range, and that my original one is malfunctioning as previously thought.

Still not feeling really comfortable using glucose meter readings as the primary basis for determining how well managed Hairy's diabetes is or using it as the basis for adjusting dosage.

 

The Secondary Monitoring Tools in my signature link give some 'softer' assessments which may be used.

The clinical signs - excessive eating, excessive drinking/amount drunk, excessive urination, glucose in the urine, ketones in the urine, and weight loss have been used to adjust insulin dose, too, in this document at the U of Queensland.

No one measure may be perfect, and short of having lab equipment in your home, home glucometers are more quantitativ than the clinical signs. Your cat is more than a number, though, so using all the tools you can will give you a more rounded picture of how the cat is doing. Appetite, thirst, urine and fecal output characteristics, weight, breath scent, dehydration/skin tenting, activity level and more all give you a sense of how your cat is doing.

 

I have been monitoring the 5 Ps, water intake and output, eating, coat, and weight and he is doing excellent on his current dose in all of those areas. But for the most part the BG readings (on any meter) would suggest that he should be worse off than the was before starting insulin and just the opposite is the case on all other indicators.

 

How are things going with you two? Are Hairy's numbers looking better? How are his 5Ps?

 

I saw your numbers - pretty low greens. Have you told the vet? Our protocols say that anything under 50 is too low and approaching hypo territory - we usually reduce dose in that case by 1/4 unit.

If he is going too low that could explain reduced appetite - thats what happened to my Tiggy .. not what you would expect from a hypo but he stopped eating altogether and we had to stop the insulin as a result. Turned out he was in remission.

Wendy