Improving Blood Glucose (Sugar) Monitoring for Diabetes

by Food and Drug Administration (FDA)

When most people sit down for lunch, the only guidance they seek is from the menu. But for an estimated 1 million Americans who are diagnosed with Type I diabetes mellitus, lunch — or any other meal — starts with a test using a portable device called the blood glucose meter.

Self-monitoring of blood glucose (a sugar) is called SMBG for short. Most insulin-dependent diabetics carry out SMBG four to seven times a day, as it is crucial to treatment of the potentially degenerative disease of diabetes. Properly executed, SMBG enables the users to modify the type of food they eat, vary the amount and time of exercise, and adjust medications. SMBG, which is also recommended for some diabetics who have non-insulin-dependent diabetes (known as Type II), enables the physician and patient to clearly define treatment goals and to measure the effectiveness of therapy with minimum disruption of daily life.

Yet, some diabetics have had difficulty following the procedures involved with self-monitoring of blood glucose. Complaints, which started reaching the Food and Drug Administration's Center for Devices and Radiological Health in the mid-80s, raised questions about the accuracy of blood glucose readings obtained by diabetics at home, and caused concern about the impact on treatment regimens. For the past three years, FDA has been trying to find out why errors occur in SMBG — and the search is now almost finished.

Major Advance

Diabetes, which in some forms is genetically linked, reduces the level of insulin needed to deliver energy-rich glucose to the cells of the body. In its mildest form, Type II diabetes can go practically unnoticed — an estimated 5 million American diabetics have never been diagnosed and are presumably unaware of their illness or of the long-term health consequences. But the most severe type of diabetes mellitus, Type I, characterized by insulin dependence, can lead to blindness, gangrene of the extremities, kidney dysfunction, arteriosclerotic heart disease, and, if these complications are untreated, death.

For the 10 percent of America's 11 million diabetics — and a similar proportion of the 200 million diabetics worldwide — who closely watch their glucose levels, blood glucose meters represent a major advance. Traditionally, a urine test strip was used at home by diabetics to monitor glucose levels. However, its results were indirect, measuring spillover of sugar in the urine, and for Type I diabetics it was of only limited use for total diabetes management. Generally, only high glucose levels could be detected.

Blood glucose measurements were introduced for home use in the late 1960s, enabling diabetics to detect high and low blood sugar levels by visually noting color changes on a chemical test strip from a single drop of blood.

By the late 1970s, the evolution to a portable meter to "read" the chemical strips was complete, and a new trend in diabetes management was born. The blood glucose meters, sold over the counter in pharmacies and grocery stores today, detect the glucose level in the blood on the strip and provide immediate warning about the onset of hyper- or hypoglycemia (high or low blood sugar). Experts agree that measuring glucose in the blood is a more preferred method than measuring it in the urine.

Moreover, the meters include many features designed to make self-monitoring convenient. Many operate on batteries and are small enough to fit in a purse or a shirt pocket and can be used almost anywhere. Some contain electronic memory, and more advanced models even have built-in modems for transmitting the test results to the diabetic's physician.

The Procedure

With most of the meters, the process of SMBG takes just a few minutes. For some meters, the first step is to calibrate the meter for the particular batch of test strips being used. Then, as with the use of visual test strips, the user obtains a drop of blood by pricking a clean finger with a puncture device and places that drop of blood on the chemically treated pad of a testing strip. The user starts the meter, which measures the exact time necessary for the chemicals in the pad to react to the blood. Several seconds later, the meter alerts the user to blot or wipe the excess blood from the pad of the test strip. At another signal from the meter, the user inserts the strip in the meter. Shortly afterward, the display window shows the glucose level in the blood. Some older SMBG systems require wiping or blotting of blood from the test strips, but new technology has eliminated this step from the procedure. For these new meters, once the blood is placed on the test area, the meter times the reaction and delivers a glucose reading.

Complaints

While SMBG has proved its worth for hundreds of thousands of diabetics, there have been many complaints about inaccurate results and difficult meter maintenance. The manufacturers of the meters are obligated by law to report such occurrences to FDA, which regulates medical devices and monitors medical devices that present problems for users.

User error seems to be involved in many complaints about inaccurate results. Various age- and diabetes-linked physical problems of the l million users of blood glucose meters raise further questions about the number of diabetics who might have difficulty in performing the steps for the use of the meter. According to the American Diabetes Association, about 27 percent of diabetics are visually impaired, and 25 percent have loss of sensation in hands or feet or problems in moving fingers. Many diabetics have a low education level with below average reading skills. In addition, a substantial number of diabetic patients are Hispanics with a limited command of English.

As Joseph S. Arcarese, director of CDRH's Office of Training and Assistance noted, "the reports of inaccurate readings with the use of blood glucose meters are the largest medical device user problem reported to FDA. We know something is going wrong. The question is, what?"

Search for Answers

An important early step in the search for answers was a special November 1986 conference of organizations most directly involved in the problems of diabetics — the American Diabetes Association (ADA), FDA, the Centers for Disease Control, and the National Institute of Diabetes and Digestive and Kidney Diseases. This Consensus Development Conference on Self-Monitoring of Blood Glucose, attended by many health professionals and representatives from the medical device industry, probed questions about the usefulness and efficacy of SMBG under conditions ranging from use in hospitals to use in summer camps by children with diabetes.

The principal conclusion, according to John A. Colwell, M.D., Ph.D., the president of ADA, who chaired the conference, was that SMBG was "recommended for insulin-treated diabetics [generally, Type I]." In the view of the health professionals and regulators of the health industry, the test kits had proved their potential therapeutic value, and physicians had encouraged many Type II diabetics to use SMBG to monitor their blood glucose.

The second most important finding of the conference was that the blood glucose meters should be made easier to use, and that the users should be better trained in their operation. "We did not have much [research] data," Dr. Colwell recalled, "but we felt that there was a tremendous need for better user education."

FDA Studies

Following the consensus conference, FDA conducted several in-house studies. One probed the reliability, accuracy and precision of 14 marketed portable meters. An analysis of the meters by FDA's laboratory in Baltimore showed that, with minor exceptions, they performed as they were supposed to when used according to the manufacturer's directions. But an in-house FDA study of instructions included by the manufacturers with the meters strongly suggested that much of the material did not adequately give the users the self-monitoring guidance they needed.

The specific problems faced by diabetics emerged only from a detailed user analysis of a sample of nine meters and their accompanying instructional materials by the Pacific Science and Engineering Group in an FDA-sponsored study, "Human Factors Analysis of Blood Glucose Monitoring." With the final report near completion, preliminary conclusions show that FDA was on the right track. In the FDA findings, approximately two-thirds of the experienced users made significant errors. The main factors behind the inaccurate readings appear to be inadequate training in the use of meters and misunderstanding of the manufacturers' instructions leading to errors in the operation of the meter.

Common user errors were:

• failure to follow the manufacturer's procedures
• inadequate amount and placement of blood on the test strip
• failure to calibrate the meter
• lack of cleaning
• use of outdated strips.

About the Author

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FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.