Self-Monitoring Blood Sugar: Is ‘Second Drop’ and Squeezing Finger to Draw Blood OK?

I’ve been regularly testing my blood sugar at home for nearly a decade now. At times when I get an error message on the glucometer (thanks to incorrect technique but more often because of insufficient blood), I never hesitate to squeeze out a second drop of blood on a fresh strip to get a “proper” reading. All the while I was blissfully unaware that both my actions are a matter of debate in Diabetes Self-Management Education (DSME) pundits.

It seems there is no general agreement regarding the use of the first or second drop of blood for glucose monitoring. The American Diabetes Association and other groups say that people should thoroughly wash and dry their hands, and then test the first drop of blood that comes from the finger. However, they do not have advice on what to do when you cannot wash your hands.

Now a new study suggests if soap and water are nowhere to be found, using the “second drop” of blood may be OK.

As for squeezing the finger, the researchers found that too much pressure did appear to interfere with accurate test results. On average, blood sugar readings were lower when people put pressure on the finger. The finding, according to the researchers, is in line with advice to avoid firm squeezing of the tested finger.

For the study, Dutch researchers at the Isala Clinics Diabetes Center at Zwolle in the Netherlands had 123 people with diabetes test their blood sugar under various conditions: after thoroughly washing and drying their hands; without hand washing; after handling fruit, which leaves sugar on the fingers; and after washing their fruity fingers.

The participants also tested their blood sugar using varying amounts of pressure to squeeze a drop of blood from the tested finger. (In general, guidelines advise against squeezing the finger too hard to get a blood drop because it may distort blood sugar readings.)

Overall, the study found, clean hands and the first drop provide the most accurate result. But compared with tests of clean hands, 11 percent of study participants had test results that were at least 10 percent off when they tested the first drop of blood from their unwashed hands. The same was true of 4 percent of study participants when they used the second drop of blood.

Based on that, the researchers recommend that people wash and dry their hands before testing, then use the first blood drop. But if they cannot wash up for some reason, it’s “acceptable” to use the second drop after wiping away the first.

But what about fruity hands? In that case ‒ or whenever hands are visibly dirty ‒ a good washing is necessary, according to the researchers. They found that when study participants tested fruit-exposed hands without washing, 88 percent had blood sugar levels that were at least 10 percent off from their clean-hand readings ‒ at least when using the first drop of blood.

They fared better when using the second drop. But 11 percent still had results that differed substantially from their clean-hand measurements.

As for squeezing the finger, the researchers found anywhere from 5 to 13 percent of study participants had a significantly different blood sugar result (versus no squeezing), depending on how much pressure they put on the finger. On average, blood sugar readings were lower when people put pressure on the finger. The finding, according to the researchers, is in line with advice to avoid firm squeezing of the tested finger.

The findings are published in the early online edition of the journal Diabetes Care.

SOURCE: Diabetes Care

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