Type 1 Diabetes: Complications

Managing Diabetes with a Visual Impairment

By Mark Uslan, Caesar Eghtesadi, Angie Spiker, Karla Schnell, and Darren Burton.

The authors would like to thank the Joslin Diabetes Center of St. Mary's Hospital, Huntington, WV, the Marshall Diabetes Center of Cabell Huntington Hospital, Huntington, WV, and Detra Bannister of AFB TECH. Funding for this product evaluation was provided by the Teubert Foundation, Huntington, WV.

Diabetes is a disease in which the body is unable to use and store glucose properly. It is a serious health problem in the United States—16 million people have the disease, and over 5 million of them experience some form of vision loss. Using devices that measure their blood glucose levels enables people to keep those levels within a normal range by taking a dose of insulin or eating a certain food. Blood glucose meters have revolutionized diabetes care by allowing individuals with diabetes to have more active control over their condition.

Why is an accessible blood glucose meter so important? The answer is simple: If you are not able to operate the meter and read the results, the meter is not usable. There are about 30 blood glucose meters on the market, including a few that have speech-output capability or can be used with a separately purchased speech module. Some visually impaired people may be able to use an off-the-shelf meter without speech output, but others with less vision need speech access to test their blood independently.

For this evaluation, we acquired and examined 16 blood glucose meters, including the ones that have speech output capability. We identified which meters to acquire by using published reports and physicians' recommendations. To help us understand the devices, we observed blind or visually impaired people using their blood glucose meters and then interviewed them. We identified the key features to look for in a meter, rated the meters that offer speech output and five that do not, and considered the state of the technology of blood glucose meters, including what next-generation devices may be like.

We first review five off-the-shelf meters to identify those that have the most usable features for people who are visually impaired. We also give you background on how meters work, what to look for, and how the technology will be changing in the coming years. We then review meters that offer speech-output capability and show how blood glucose meters are being used by four visually impaired individuals.

How a Blood Glucose Meter Works

Today's blood glucose meters use an enzyme found in the blood to measure glucose levels. The glucose in a drop of blood placed on a test strip reacts with the enzyme, and this reaction is measured by an electric current generated by the reaction. The conventional means of self-testing one's blood glucose level is the finger stick method. To perform finger-stick blood glucose tests, you need a meter, a lancet device, disposable lancets that enable you to draw a drop of blood in a controlled way, and a set of test strips.

Before you use a blood glucose meter, you need to calibrate it to the test strips—every time you open a new container of test strips and before the first strip is used. Some meters require that you push a button until the number that appears on the screen corresponds to the number located on the test-strip container. Other meters use strips that come with an encoded key or strip that allows you to calibrate the meter by inserting the encoded key or strip into a slot in the meter.

After the test strip is inserted into the meter, a blood sample is obtained using the lancet device. Typically, you draw blood from the tip of the finger, but some newer devices allow you to use the forearm, upper arm, or thigh. Then, blood must be applied to the target area of the test strip, which is tiny—sometimes no larger than a few square millimeters. In 5 to 50 seconds, depending on the device, the blood glucose reading (a two- or three-digit number) appears on the meter's display.

Desirable Features of Blood Glucose Meters

Code Key Calibration

Although test-strip calibration is done only once with each new container of test strips, it can be a hassle to do, especially if you can't see the meter display or the code on the container of test strips. Meters that use an encoded key or strip make life a lot easier.

Adjustable Lancet Depth

Each meter comes equipped with its own lancet device and a few disposable lancets. The lancet depth should be adjustable to control the puncture depth, an important feature for reducing discomfort and the need to repeat the test.

Blood Sample Size

Newer meters usually require from 0.3 to 4.0 microliters of blood—much less than the typical 10.0 microliter sample of older models. Since the manufacturers assume that verification of sufficient blood on the strip will be done visually, a smaller sample size gives the visually impaired user better odds of getting enough blood on the strip and reduces the need for retesting.

Capillary and Touchable Strips

The task of applying blood on a test strip can be difficult. It is particularly hard to do if the strips are so sensitive that you cannot touch the test area of the strips, which is the case with some meters. The task is made much easier if the meter uses touchable strips. In addition, it is also easier to apply blood on a strip if the strips are designed to take advantage of capillary action, which draws the blood on the strip.

Ability to Apply More Blood After the Test Starts

Some meters allow you to apply more blood to the test strip after the initial application, in case not enough was initially applied. This feature diminishes the need for retesting.

Cleaning

To remain accurate, some meters need to be cleaned of residual blood that may have gotten on sensitive parts of the meter. Other meters are designed so that these components are not exposed, thereby eliminating the need for cleaning.

Response Time

The response time is the amount of time it takes the meter to provide a reading after the blood is applied. Shorter times make testing less of a hassle in our fast-paced world.

Whole-Blood versus Plasma Readings

Plasma-calibrated meters convert whole-blood readings to plasma-equivalent values, the standard used by health professionals. Plasma-calibrated meters make it easier for patients and their health care professionals to keep track of their progress.

Size/Portability

Active people need the convenience of being able to put a meter into their pocket or pocketbook. Some meters are as small as a pager, while those with speech modules are much larger but still portable. Though all meters use small LCD screens that are not easy to view, the font size on the screens is typically large and bold.

Accuracy and Consistency

The results of the tests of accuracy and consistency of 11 popular meters were published in the October 2001 issue of Consumer Reports. The article defined consistency as "the ability to give similar readings on successive tests of the same blood sample" and accuracy as "how closely the readings agreed with the standard lab results" (p. 38).

Downloading Capability

All meters have the ability to keep test results in memory. In some, the data can be downloaded to a computer and translated into charts or other simplified forms, which can be a helpful tool for patients and their physicians.

Cost

The average meter costs between $50 and $70, and many come with rebates that can significantly reduce the cost. However, expect to pay 5 to 10 times as much if you need speech. The small test strips on which the blood is applied are also a major cost component, especially if you need to test your blood many times a day. On average, they cost from 65 cents to 90 cents apiece, with a new one needed for each test. The disposable lancets must also be purchased separately, but they cost only a few cents apiece. Health insurance covers all the components but may limit the choices of meters.

Five Off-the-Shelf Blood Glucose Meters

We tested 5 meters from among the 16 we acquired. Three were the top picks by Consumer Reports, and the other 2 were the ones from among the 16 that had the largest fonts. Consumer Reports highest rated, in rank order, are the One Touch Ultra from LifeScan, the Accu-Chek Advantage from Roche Diagnostics, and the FreeStyle from TheraSense. The meters with the largest fonts from among the 16 we acquired were the Prestige IQ from Home Diagnostics and the Sof-Tact from Medi-Sense. The Prestige IQ was not rated by Consumer Reports, but its predecessor was, and the manufacturer says that the Prestige IQ uses the same testing technology (see Consumer Reports, October 2001, p. 37).


Caption: From left to right: One Touch Ultra, Accu-Chek Advantage, FreeStyle, Prestige IQ, and Sof-Tact.

The figure is a photograph of five blood glucose meters. The meters are arranged with the smallest on the left and the largest on the right.

The Sof-Tact was not rated by Consumer Reports because it is so new. It uses a testing method that combines all the separate steps of blood glucose testing. You press the meter onto the test site (the base of your thumb, your forearm, or your upper arm) and push a button. The meter creates a vacuum against the skin, obtains a blood sample with its built-in lancet, and then applies the blood to its internal test strip. The unit can also function in the standard way, using the finger-stick method. We looked at the Sof-Tact's automated approach to testing.

The advantages of the three meters that were rated the highest by Consumer Reports are that they are all small and lightweight and were rated "very good" in both accuracy and consistency. The accuracy and consistency of the testing technology used in the Prestige IQ was also rated by Consumer Reports; that meter was rated "fair" in accuracy and "poor" in consistency.

Since all meters on the market use LCD displays, none offers particularly good contrast; in addition, the displays cannot be viewed at a side angle, and the screen is not visible outdoors in sunlight. On the positive side, they all use relatively large fonts. The meter with the largest font is the Prestige IQ. Its font is .78 inches tall and .13 inches thick, which is 24% larger in height and 54% thicker than the largest and thickest of the next best, the Sof- Tact. The three meters chosen by Consumer Reports used fonts that were smaller— approximately 18% shorter and 29% thinner than the Sof-Tact.

As for ease of use, we found that the Ultra and the FreeStyle have the fastest response time and use the smallest blood sample. But the Advantage had other useful features: a code key for calibrating the meter, a tactile notch on the test strip to help feel where to apply blood, and the ability to add more blood after testing begins. The Prestige IQ lacks features that make it easy to use. The Sof-Tact is the easiest to use of the meters we tested because it does not require you to apply blood manually on the test strip. Unfortunately, we do not have feedback from users on how well this new device works or whether the testing process is more painful, the same, or less painful than the standard finger-stick method.

The Bottom Line

Off-the-shelf blood glucose meters, such as the One Touch Ultra, the Accu-Chek Advantage, and the FreeStyle, are highly portable, accurate, and consistent. They leave something to be desired when it comes to ease of use and font size, however. The Prestige IQ offers the largest font, but doesn't measure up to the other meters in either ease of use or accuracy and consistency.

The Sof-Tact is the most interesting of the meters we evaluated because its automated approach makes it the easiest to use. However, since it uses new technology, the real test is feedback from users. Until we hear from Sof-Tact users whether they like the device, we prefer to say that it shows much promise. In addition, at present the only data on accuracy is available from the manufacturer by calling 866-763-8228 and requesting a white paper. But if you are in the market for a blood glucose meter and can consider an off-the-shelf system, speak with your physician or certified diabetes educator about the Sof-Tact. Keep in mind that the Sof-Tact is about $200, which is considerably more expensive than the others. If you prefer to stay with the tried and true, we recommend the Accu-Chek Advantage, since it has been well tested and has the most ease-of-use features. Of course, the best way to determine if you can read the display is to view the meter before you buy it.

From Access World: Technology and People with Visual Impairments, (September 2002, Volume 3, Number 5). Reprinted with permission of the American Foundation for the Blind. Available free online at www.afb.org. Funding for this product evaluation was provided by the Teubert Foundation, Huntington, West Virginia.