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Better Control with Fructosamine?

New At-home Test Gives 2-3 Week Look-back

By David Mendosa

Last Update: August 21, 2002

A new meter that gives you the first measure of overall glucose control without relying on laboratory testing became available last year. And what promises to be a much more user-friendly model is due out later this year.

Fructosamine tells you your 2-3 week average.

Paying close attention to overall glucose control is the key to managing diabetes. The 1993 Diabetes Control and Complications Trial showed that keeping blood glucose levels as normal as possible is the best strategy to reduce the risks of complications.

Unlike blood glucose meters—which measure only how you are doing at that moment—and hemoglobin A1c tests—which measure blood sugar over a period of months and must be done in a laboratory—this new meter can immediately tell you your blood sugar average for the past two to three weeks. By testing weekly you can quickly see the results of new medications and diet.

This new at-home test measures fructosamine, which the manufacturer, LXN Corp. of San Diego, calls GlucoProtein. It measures the amount of glucose attached to albumin and other serum proteins, which last only about 17 to 21 days in the bloodstream.

Clinical laboratory fructosamine tests have been available since the mid-1980s. But LXN's new Duet Glucose Control System is the first that lets you do the test at home. LXN's meter is called the Duet, because it does two tests: both fructosamine and blood glucose, using different test strips.

The Duet's fructosamine test takes a relatively large drop of blood compared to blood glucose meters—25 microliters—and gives the result in four minutes. Still, that's a lot less than laboratory tests require.

The meter's blood sugar test takes 10 microliters of blood, which is more than other meters on the market. But it gives the result in as little as 8 seconds, which makes it the world's fastest glucose test.

The Duet is also somewhat larger than other meters on the market. It's 3" by 5" and 1.5" deep.

It lists for $299, including 25 glucose test strips and 4 GlucoProtein test strips. LXN offers a $50 rebate for your old meter. Vials of 100 Duet glucose test strips list for $90; 16 GlucoProtein test strips are $128. According to LXN, however, one retailer, Wal-Mart, is offering the Duet at $238 less a $100 coupon rebate. LXN's toll-free number is (888) 596-8378.

The Food and Drug Administration approved the Duet in 1997 based on LXN studies that show that its fructosamine results are as accurate as the standard clinical laboratory test and that the variation from one test strip to another is no greater than 10 percent. That means your actual fructosamine level could be 20 to 25 points higher or lower than the test results, says CEO Randy Nelson.

More than 97 percent of the company's sales of its Duet meter have been to healthcare professionals, says Nelson. Yet a Diabetes Wellness Letter survey of a dozen endocrinologists who have an Internet presence found that most of those who responded had never heard of the Duet and only one used it in his practice.

In spite of LXN's data, several endocrinologists expressed concerns over fructosamine's accuracy. Most of those who use laboratory fructosamine tests use them in gestational diabetes, which ironically is one use that the FDA has not yet approved for the Duet meter.

"I have no experience with the Duet meter," replies Tom Dorsch, M.D., an endocrinologist in Peoria, Illinois. "I think fructosamine testing is helpful in pregnancy, because we are changing insulin doses very often, and it is a very dynamic situation during pregnancy. I do not do fructosamine on non-pregnant patients, but I think many patients on oral agents could do very well with a fructosamine test once a week, rather than blood sugar testing periodically."

The one endocrinologist we contacted who uses the Duet meter in his practice still has questions about it. "Despite doing 1,500+ tests in the office and having some patients test at home, we have run into a few too many inexplicable situations," says J. Joseph Prendergast, M.D., the medical director of the Endocrine Metabolic Medical Center in Atherton, California.

Some type 2 patients could appropriately do a fructosamine test every two weeks instead of frequent glucose tests, Dr. Prendergast believes. However, he does not recommend it for people with type 1 diabetes, because "their intermediary metabolism is so bad."

The problem for Dr. Prendergast and his patients may be largely a question of technique. "We think we are doing it by the book, and still have these questions," he says. Nevertheless, "I'm trying desperately to like it."

The Duet is "very technique driven," acknowledges LXN CEO Nelson. It requires use of a blood sampling straw to collect the appropriate amount of blood. You touch the straw to the strip but can't tap or blow on it, he says. You should not milk the finger to get a blood sample.

Several people with diabetes who use the Duet reported problems with their technique. "I was told that the meter is very sensitive, so by squeezing blood from the finger and/or tapping the straw on the strip, one can get significantly different results," says Buzz Wolf in Huntington Beach, California, who says he isn't sure if he is past the learning curve yet. "I do question the accuracy, as I generally test twice and get 75 point differences."

On the other hand, Karen Wheelock in Colchester, Vermont, says she uses the meter to test fructosamine every three to four weeks "and it's right on the money with my most recent lab A1c." She "just loves" the meter and was impressed with LXN's customer service.

There's a good reason why people with diabetes may like the Duet meter more than their endocrinologists. "It's better to use fructosamine for home testing because you can adjust your diet or medication within a relatively short time. A1c is better for your doctor because he only sees you every four to six months and wants a long-term measurement," a satisfied user writes on the newsgroup.

LXN is hoping for even greater user acceptance of their second-generation meter, which the company expects to market in the third quarter of this year. Tentatively named the Duet II, this meter will be about one-third the size of the Duet and will retail for $90 to $100, Nelson says.

More importantly, it will be more customer friendly. "We are testing the Duet II without using a straw, and we are trying to get below 10 microliters of blood," he says.

"It will still do the glucose test in 8 seconds or less and the fructosamine test in 4 minutes," Nelson concludes. "But we are hoping to get away from these little idiosyncrasies that people have mentioned with the Duet." 

Comparing the Tests

The three ways of measuring blood glucose levels show changes in glucose control over different periods. Blood glucose meters provide a snapshot of your blood sugar at the time you test. The GlucoProtein (fructosamine) test measures the average of your continuous blood glucose levels over the past two to three weeks. The hemoglobin A1c (or HbA1c or glycosylated hemoglobin) test measures a longer period. Originally, scientists thought that test gave you a three-month average, but it now appears to be closer to four to eight weeks, according to William C. Biggs, an endocrinologist in Amarillo, Texas. Also, keep in mind that hemoglobin A1c tests are not standardized from lab to lab and may provide somewhat different results from those shown below.

Blood Glucose Meters


Milligrams of glucose per deciliter of blood (mg/dl)

GlucoProtein (fructosamine)

Micromoles of fructosamine per liter of blood (�mol/L)

Hemoglobin A1c

Percent of glycated hemoglobin of total hemoglobin































Source: LXN Corp., San Diego.

This article originally appeared in Diabetes Wellness Letter, February 1999, pages 3, 6.


In 2002 LifeScan bought LXN and discontinued all of its products including the In Charge and Duet meters. It also recalled all GlucoProtein (fructosamine) test strips because they may produce false highs.

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