The usual problem with using one of our fingertips to check our blood sugar is that it hurts. Our fingertips need to have lots of nerve endings because we use our fingers as fine sensing devices.
That's why people with diabetes got excited about using alternative test sites about 15 years ago when blood glucose meters that require just 1 microliter or less of our blood first became available. These sites have far fewer nerve endings, so any pain from testing there is uncommon. But researchers soon discovered that the alternative test sites we were using, like the forearm, had one serious limitation.
Our fingertips detect a change in our blood sugar level first, and these alternative sites can sometimes lag by more than a quarter of an hour, as I reported in an article, "Lag Time in Alternativeland," on my website in 2001. While that wouldn't matter much when our blood sugar is steady, if it were falling into the hypoglycemic range, the consequences could be serious. That's why some meter manufacturers have generally recommended since then that we don't use alternative sites if our blood sugar is likely to be falling. Unfortunately, we are unlikely to know if we are going hypo unless we test.
Now, however, Genteel has found two new alternative test sites on each hand that have little or no lag from our fingertips. These sites are on the fleshy areas of our palms on a line between where the thumb joins the palm and the center of the wrist (technically know as the thenar), and fleshy area along a line connecting where the pinky joins the palm to the wrist (technically the hypothenar) as shown below.
Genteel is the company that recently introduced the revolutionary "gentle lancing instrument" that I reviewed here starting in June with "Gentle Testing for Diabetes." Dr. Christopher Jacobs, the engineer who heads Genteel, conducted the tests, which he just shared with me.
The Genteel study recruited 24 test subjects, including people with well-controlled diabetes, pre-diabetes, and so-called "normal" people. The study took simultaneous blood samples from traditional alternative site such as the forearm and the calf/knee, from the fingertips, and from the thenar/hypothenar areas.
Before the researchers made the first blood draws, each of the test subjects sat for 15 minutes and then consumed the standard 15 gram load of fast-acting glucose. Then at 5 minute intervals, the researchers simultaneously measured blood sugar levels from alternate sites, fingertips, and either the thenar or hypothenar areas. After testing at 5 minute intervals for 1 hour, they increased the test intervals to 10 minutes for another hour or until blood glucose levels returned to at or near baseline levels, whichever came first.
Here is the graphic evidence of the comparative results of five of the test subjects. Dr. Jacobs gave me similar tabular data for the other test subjects with similar dramatic differences between alternative sites and fingertips/thenar/hypothenar areas.
Figure 1.1: Measuring Rate of Change Between Calf/Knee (Alternate Site), Fingertip, Thenar and Hypothenar Eminence of Palm - #17
Figure 1.2: Measuring Rate of Change Between Calf/Knee (Alternate Site), Fingertip, Thenar and Hypothenar Eminence of Palm - #31
Figure 1.3: Measuring Rate of Change Between Calf/Knee (Alternate Site), Fingertip, Thenar and Hypothenar Eminence of Palm - #23
Figure 1.4: Measuring Rate of Change Between Calf/Knee (Alternate Site), Fingertip, Thenar and Hypothenar Eminence of Palm - #27
Figure 1.5: Measuring Rate of Change Between Calf/Knee (Alternate Site), Fingertip, Thenar and Hypothenar Eminence of Palm - DG
In summary, blood sugar levels from the thenar and hypothenar areas of each hand consistently matched those of the fingertips well within meter accuracy. Both areas had matching bell-shaped curves reaching about the same growth rates and peak levels at the same times. The traditional alternate sites not only lagged behind both the thenar and hypothenar areas by about 22 minutes, but only reached about 70 percent of the rise from static levels to peak values.
When you check your blood sugar on your fingertips with the Genteel lancing device, you are unlikely to feel any pain. Therefore, you might wonder what advantage that using the thenar and hypothenar areas might have. The other problem is that constantly using fingertips to check our blood sugar can leave them bruised, calloused, and with reduced tactile sensation.
Still, when we switch to the thenar and hypothenar areas, blood does not rise easily or readily to the surface without using the specific technology in Genteel's lancing instrument. With this technology, comfortable and accurate blood draw is now available, allowing our fingertips to heal and regain sensation.
Dr. Jacobs continues to research these findings. He tells me that if you would like to be informed of the latest results, you can go to firstname.lastname@example.org, provide your email address, and add the note, "Palm Research Results." He promises to keep you up-to-date on further developments in his breakthrough research.