Hometesting - add 40 to results?

I talked to the vet tech yesterday and she said that they add 40 to the result that they get from their human glucometer. Is this true? Should I be adding to my results at home?

I apologize if this has already been asked but I am still learning my way around

 

I don't think I've ever heard that before.

I've used many meters and in the past have brought them to the vet with me and Tucker and the difference was minimal. My own vet no longer asks to do curves or tests for Tucker's BGs, I simply send her my own spreadsheet once in a while.

Maybe others can offer some information.

 

Never have I heard of adding 40 to the test results because it is a cat being tested on a "human" glucometer. Seems to me that just inflates the test result number for no good reason.

~M

 

The Rand protocol (I don't have a link handy here at work, but maybe someone else here does?) says a human meter is about 30% off, so they recommend adding around 30 on the low end of numbers but not adding to high numbers. For example, in the Rand protocol, the good range is 50-200 on a human meter, 80-200 on a pet meter like AlphaTrak.

 

I have heard conflicting stories about how "off" readers are. You can get 6 different results from 3 different meters in a matter of minutes. My own vet told me that human meters read a little high as a safety precaution.

I have always just gone by what number the glucometer spits out at me. That way you won't confuse yourself looking at your charts, "Did I remember to ad 40 this time?"

 

That makes me feel better, because I was just going by the results the meter gave me. Thanks

 

Here's the link: http://www.uq.edu.au/ccah/docs/diabetesinfo/link4.pdf Note that they even separate pages of the protocol guidelines for human meters (p. 2-3) and feline meters (p. 4-5).

 

Tara,

This is what I was reading yesterday too, but that was before I had even heard of AlphaTrak. So am I reading this correctly that I should only add 30 to the numbers if I am using the AlphaTrak feline meter? I am not sure if I read this correctly.

 

No, it's the other way around: you would add 30 (especially at the low end of the scale, at high end it isn't as significant a difference) if you are using a human meter. In theory, 100 on a human meter would equate to 130 on an AlphaTrak (or other feline meter). But since most human meter users on this board don't do that, from what I can tell, it's probably not necessary to bother. Not to mention, meters have some variance of their own anyway in either direction.

(Personally, I use the AlphaTrak. I like it a lot b/c it only needs the teeniest little drop of blood, but dang the strips are expensive!)

 

Hi Paige -

We tested my meter against my vets Alpha Trak when Six was first DX. I kept getting HI readings which meant his BG was over 600. My vet wondered if it was my meter (we were using an old true track left over from a previous DC).

Six went in along with my meter for a day.

Turns out, my meter was wonky (probably because it was old). At the lower numbers it was reading within 5 -10 of the Alpha Trak and at the higher numbers (300+) our old meter was adding on 100+ compared to the Alpha Trak.

I ended up buying an Alpha Trak and I like it, but if I knew I had a reliable human meter I imagine I would like it just as much.

 

As I understand it, human meters are designed to be "cautious." That means, when a person's glucose is getting high, the meter is calibrated in a way that tells you it is somewhat higher than it is. On the other end, wanting people to take action when they are getting too low, meters are calibrated on the low end to give readings lower than actual.

What I have just begin wondering about is hematocrit. Human meters are designed to work within normal human hematocrit levels. But cats and humans have different hematocrit levels. The Wavesens Presto, which we are using now, claims to compensate for hematocrit and for temperature.

 

Regarding human meter reading intentionally low, a couple of years ago someone on the board contacted a few human meter manufacturers. They said there meters do not intentionally read low. Human meters are FDA approved devices and the manufacturers said it would be against FDA rules to have the meter intentionally read low.

 

Hmm. While I believe they said that, it doesn't mean I believe it's true. LOL! They do have a 20% window of accuracy within which to meet FDA rules and that they would play within those limits would not surprise me at all. But would they admit to it? Well, that's another question altogether!

 

What is your basis for saying the meters intentionally real low? I have never seen any facts that support that even though it is mentioned a lot. The meter manuals I have seen give a limit on the HCT for which the meter is accurate. The limit I have seen is outside the normal feline HCT levels. My One Touch Ultra 2 meter says it reads within HCT range of 30 t0 55%.

 

I actually didn't say that the always read low. What I said (which I was told by a human doctor) is that the meters read a little low on the low end (so a person will take some action earlier rather than later to address possible hypoglycemia) and a little high on the high end (for a similar reason). This would really be sensible if you were trying to catch problems earlier rather than later.

I'm not an expert and am relying on my memory here, but I thought normal hematocrits for cats wre somethng like 30-40. Humans are higher. If a meter does not take hematocrit into account, presumably it will assume an average human hematocrit, which will be higher than an average feline one.

 

I've been tracking results of my OTU against the AlphaTrak for awhile now. I test at the same time, although with different drops of blood (same ear, pricks next to each other).

In general, I'm seeing the OTU read lower that the AlphaTrak at lower numbers, but then there's a break point where the two meters give nearly identical results. I don't have all of the data in front of me right now, but here are some of the results. It's been pretty consistent.

OTU --- AlphaTrak
------------------
36 ----- 59
61 ----- 78
73 ----- 87
84 ---- 116
90 ---- 119
154 --- 171
165 --- 196
262 --- 270
268 --- 266
402 --- 382

What that tells me is that the AlphaTrak user needs to be mindful of this when hearing the commonly espoused "hypo" numbers (i.e., 40-50 or less, or whatever is currently being quoted). For an AlphaTrak user, the comparable number where they need to take action against hypo will be higher (perhaps 70 or 80).

Beyond that, I think it's important to use the same meter consistently and to test the meter using control solution periodically.

The values above were using the same vial of AlphaTrak strips, but the OTU strips were from multiple vials (codes 17 and 25). There was a slight difference per OTU vial, but I don't think it was statistically significant.

I use the OTU as my day-to-day meter but double-check against the AlphaTrak if I have any questions or just want a "second opinion."

(Edited to make numbers more readable.)

 

Regarding One Touch vs AlphTrac, how do you know that the One Touch reading is more accurate than the AlphaTrac and thus a higher low warning is required for the AlphaTrac. Maybe the AlphaTrac is more accurate and the error is with the One Touch.

Regarding BG measurements in general, there is a significant difference in the distribution of glucose in the RBC portion and liquid portion of the blood. The vet's lab measure the glucose in the liquid portion only. The meters measure it on whole blood. The variation is:

Species Glucose Concentration in RBCs Glucose Concentration in Plasma
Human 42% 58%
Canine 12.5% 87.5%
Feline 7% 93%

 

Actually, I'm NOT saying one is "more accurate" than the other. My point is that most people here use human meters and come to see 50s and 60s as "normal" (just look at the results that are seen in civvies). However, those same cats might test in the 70s or 80s on an AlphaTrak, meaning those values are "normal" for the AlphaTrak meter. It's a frame of reference issue, so to speak, and an AlphaTrak user needs to not take the commonly quoted "a hypo is below 40" or "a hypo is below 50" mantra too literally (IMHO). I mentally adjust my expected target range when switching between meters -- i.e., I'll intervene if see the 30s or 40s on the OTU but perhaps intervene if I see the 50s or 60s on the AlphaTrak. I actually EXPECT them to read differently, for some of the reasons you stated, therefore I adjust my expectations (and actions) accordingly. Make sense?

ETA: Testing my civvies gives me a clue about what to perceive as "normal" range for the meters. And yes, I'm assuming that my civvies have "normal" BG values. I don't much care what those particular values are -- I'm just establishing a baseline for comparison when giving exogenous insulin to my diabetics.

 

This topic (or one much like it) has come up repeatedly over time. There is several discussions about it on Think Tank on the OLD forum.

That is correct, there is a slight difference and at least in the Lantus Group that has been pointed out (we have a FEW users with the AlphaTrak) those people are aware that there MINIMUM BG is higher than what the protocol (aka Tilly) recommends. They are also told to put clearly in thier SS and signature that they are using an AT meter so dosing advisor etc. can account for that fact.

The point is the Alpha Trak is not nessisary and quite expensive. Most people are using a human meter. The Protocol for Lantus/Levemir are written with the explicit "assumption" that a human meter will be used.

This is from Roomp and Rand (dosing for cats on Lantus and Levemir). The given NORMAL range for BG for healthy non FD cats is 70-120 mg/dl (plamsa) when measuring in whole blood 60-110 mg/dl is the reference range *NOTE: this is also true for humans* A BG of below 60 is mild hypoglycemia in either species. The dosing guidlines state that If blood glucose is < 50 mg/dL (2.8 mmol/L) Reduce dose by 0.25-0.5 IU depending on if cat on high or low dose of insulin This is already accounting for the +30mg/dl discrepancy when using a human meter on a feline. The protocol can be followed without the caregiver having to make conversions or worry about meter variations. Caregivers who use the Alpha Trak are (at least in the Lantus Group) advised otherwise, the number of persons using these meter is however small. Those who have the meter usually end up setting to the side at some point and use a more resonably priced human model.

Most important is not the absolute accuracy of the device used but rather the consistancy (precision) which is why it is recommended to always use the same meter. The meters themselves are by industry standards somewhat inaccurate (FOR HOME USE ONLY) for any diabetic human or other species it is adequate, We are looking for Zip codes not house numbers.

 

I was just at my vets and took my reader, we are using the ReliOn Micro, our vet tested her two meters against mine and it was 25 points off. Both her readers were getting a BG reading of 66 and mine was 41, yes he was really low.


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Ok, I will continue to use my human meter and not confuse myself with the Alpha Trak especially since we are going to start Lantus next week.