Alternate Site Testing is the practice of drawing blood from locations other than finger tips. AST is also sometimes referred too as painless testing. Finger tips have a high concentration of nerve endings and pricking fingers can be painful. Alternate sites such as your forearm, have less nerve endings, which means virtually no pain when pricked. So you may ask, "Why is anyone pricking fingers?", well there some issues with AST and that is why you see such a varying level of support for the practice from manufacturers. I wanted to know more about AST and why the recommendations varied so much. Here is what I found.
Disclaimer: What you read here are my opinions and thoughts after studying material from manufactures and other sources. What you read is not a substitute for talking with your doctor, so please ask your doctor before considering any change in your diabetes care management.
The problems with AST
All manufacturers recommend that you do not use AST in situations where your glucose levels may be changing rapidly. Blood takes longer to work its way to the surface of your skin in AST locations than your finger tips. This can be problematic if you are hypoglycemic since your glucose levels may be much lower in your body core than a glucose test may indicate by testing blood which has had to travel though more body tissue such as your arm or thigh. Considering people have varying amounts of fat and muscle it is easy to see why manufacturers are leery of AST. Here is a complied list from several meter manuals of conditions when to avoid AST.
- If you think your blood glucose is low (hypoglycemia)
- When blood glucose is changing rapidly (after a meal,insulin dose or exercise).
- Within 2 hours of eating, exercise, or taking insulin.
- If you have hypoglycemic unawareness (lack of symptoms).
- If you get alternative site blood glucose results that do not agree with how you feel.
- During illness or times of stress.
- If you will be driving a car or operating machinery.
- If your blood sugar may be rising or falling rapidly or your routine results are often fluctuating.
- If your blood sugar may be low or high.
As you can see, the manufacturers are unwilling to recommend AST for virtually any test other than a fasting or pre-meal test. Please use the reference links in the left column of this page for more information about AST issues.
Which Glucose Meters can be used for Alternate Site Testing?
The table below list which meters are rated for alternate site testing, the number of or name of alternative sites and the required blood sample size. This information is taken from each meters owners manual and(or) company website.
|Accu-Chek Aviva||Aviva Plus||0.6||3||Ask Doctor|
|Accu-Chek Compact Plus||Drum||1.5||5||Ask Doctor|
|Bayer Contour USB||Contour||0.6||2||X||X|
|Bayer Breeze 2||Breeze Drum||1.0||2||X||X|
|FreeStyle Lite||FreeStyle Lite||0.3||5||X||X||X||X||X|
|FreeStyle Freedom Lite||FreeStyle Lite||0.3||5||X||X||X||X||X|
|One-Touch Verio IQ||OneTouch Verio||0.4||No information provided|
|One-Touch Ultra 21||OneTouch Ultra Blue||N/A||2||X||X|
|One-Touch UltraMini||OneTouch Ultra Blue||N/A||2||X||X|
|One-Touch UltraSmart 1||OneTouch Ultra Blue||N/A||2||X||X|
|ReliOn Micro||Confirm / Micro||0.3||1||X|
|ReliOn Confirm||Confirm / Micro||0.3||1||X|
As you can see, there does not seem to be a correlation between minimum sample size and the number of available testing sites. You also do not see all newer meters promoting AST over older meters. My theory is that because testing your glucose levels in any area other than your finger tip may lead to problems, the safest approach for manufacturers is not to promote AST any more than they have too, to make their product competitive. If a meter and(or) strip are not easy to use for AST due to ergonomics, sample size, strip technology or other design factors, then perhaps more strips are waisted thereby leading to lower consumer satisfaction for the product.
I think what we have here is a battle between the best diabetes care possible and the desire of manufactures to offer a product that is less painful, cost effective and does not expose them to legal liability, because no matter how well they make a meter system there is a huge unpredictable variable, the diabetic.
It is common for a manufacture to recommend a different lancet end cap for AST. These ends caps usually are clear and have a larger contact area with your skin. The clear end caps are a little shorter and you receive a slight deeper poke which is required when testing in areas other than your finger.
Which Is The Best Glucose Meter For AST?
Of all the meters I have used, I think the FreeStyle meters and strips are by far the best for AST. There are three main reasons:
- Small sample size,
- Long duration of time to get sufficient blood to the strip,
- Strip design which allows better targeting of blood for less mess.
While manufactures are often quick to point out small blood sample size requirements, there is another factor to consider. How much blood do you need actually to get that amount into the strip.
FreeStyle test strips only require a 0.3 microliter of blood and with the little arrow points on the test strips it can wick in a very tiny drop of blood and give a reading. If you do not get enough blood the first time, you can wait up to 60 seconds for more blood to become available and wick additional blood into the same strip.
When I used systems from Bayer, Accu-Chek, Agamatrix and One-Touch I sometimes had test errors due to lack of blood which resulted in a waisted test strip. It was not always because I did not draw enough blood but because I was tired, or one time hypo, and did not line up the test strip properly. This resulted in only drawing in a portion of the available blood, and before I could move the test strip to pick up more blood, the meter gave me an error.
To avoid a wasted test strip I found myself waiting for a blood sample to grow to a point where I knew it would be more than enough. After the test was done I would pull the strip from the meter and would often have excess blood on my fingers. I never had that problem with the FreeStyle Strips.
1. Lifescan does not list this information in their product manuals but does make this claim on their Alternate Site Testing Webpage.