Forearm test not good for checking blood sugar

People with diabetes who need to monitor their blood sugar levels should not use their forearm to get a blood sample if they think their levels are low, two teams report.

Although testing blood sugar levels using a forearm prick produces readings similar to those obtained from a fingerstick when levels are high or normal, it may overestimate blood sugar levels when they are low, according to two brief reports in the medical journal Diabetes Care.

In the first study, Dr. Shu Meguro and colleagues at Saiseikai Central Hospital in Tokyo, Japan, gave 10 healthy volunteers intravenous insulin injections to lower their blood sugar levels.

Measurements were made using blood taken from the fingertip, the fleshy part of the palm, and the forearm, every five minutes for 70 minutes.

The lowest blood sugar values recorded were 37 at the fingertip, 38 at the palm, and 50 at the forearm.

"Blood [sugar] measurement at the forearm should be avoided to prevent incorrect clinical decisions," Meguro's team advises. However, the palm is a suitable testing site "because it provides accurate measurements with less pain."

The second team, led by Dr. Nadine Lucidarme at the Robert Debre Teaching Hospital in Paris tested whether children preferred the palm or the forearm over the fingertip for testing blood sugar levels.

The 29 children, between 5 and 17 years old with type 1 diabetes, who were included in the study measured blood sugar four times a day in blood drawn from the fingertip and either the palm or the forearm for two weeks. Then for one month they chose whichever site they preferred.

At the end of the study period, three quarters of the kids said they preferred the alternative testing site because of easier sampling and less pain.

The testing produced similar a reading from the three sites, except during periods of low blood sugar, or hypoglycemia. When fingertip testing showed levels averaging 50, forearm testing was 11 points higher.

Lucidarme's group suggests that "alternate sites can be recommended with the caveat that forearm sampling should not be used in children with symptoms of hypoglycemia or in specific conditions carrying a high risk of hypoglycemia."

SOURCE: Diabetes Care, March 2005.