Q: I keep my blood glucose meter and testing strips in my car between patients. Will that impact the reliability or accuracy of the glucose measurements I obtain on my patients?
Blood glucose measurement equipment has come a long way over the years. The utility of these devices has improved and so has the accuracy. However, improper storage or use can lead to inaccurate blood glucose results. To prevent this, there are a few things to keep in mind regarding safe storage and handling of blood glucose measurement equipment. As with any medical device, it is important to follow the manufacturer's recommendations to assure the glucose strips and meter continue to work properly. One of the most frequent reasons for errors in glucose readings has to do with how you handle the strips. For example, Bamberg et al. (2005) studied the effect of adverse storage environments on glucose test strip performance. The researchers exposed the test strips to adverse conditions such as direct sunlight, humidity, and refrigeration and found that the stability of test strips was longer when the strips were stored in closed vials. The authors concluded that glucose test strips should be stored in the original container with the cap secured and at room temperature, as recommended by the manufacturer.
Because the outside temperature varies considerably by season and geographic location, store your equipment (meter, strips, and control solution) in the carrying case in a cool, dry place with a temperature no more than 86 [degrees]F. Also choose a place that protects the equipment from humidity, dust, and dirt. If your meter is accidently exposed to a contaminate, most manufacturers recommend that you clean the outside of the meter with mild soap and water on a soft cloth. Take care to prevent any liquids from entering the inside of the meter through the test or data ports. Following these recommendations will prevent damage to the equipment that may lead to erroneous results.
If you receive a blood glucose result that you don't expect or the patient cannot explain, there are a few things the U.S. Food and Drug Administration (FDA) (2015) recommends that you check first:
* Perform a system check to make sure the equipment is working properly. When you turn the equipment on, it automatically completes a system check. When a problem is detected an error code is displayed on the screen. If you receive an error code, refer to the user's manual to identify the meaning of the code and to determine how to correct the problem.
* You can also perform a check on the system by using control solution. Because control solution contains a known amount of glucose, you can test the validity of your blood glucose testing results. To perform the check, simply use a small drop of control solution in place of blood. The result should fall within the range identified on the test strip bottle. Use this opportunity to teach your patient how to use control solution as well. Most manufacturers recommend using control solution whenever you open a new vial of strips, if you suspect there is a problem with the equipment, or if you receive results that are higher or lower than expected.
* Compare the results from your meter with a laboratory result. When the machine is working properly and correct testing technique is followed, the results from your device should be close to the laboratory's result.
* If you suspect the machine has malfunctioned, contact the manufacturer. Most devices have a toll-free number on the back of the device that you can call for assistance.
Because improper testing technique can also lead to erroneous results, it is a good idea to periodically review blood glucose testing technique with your patients as well. For example:
* Make sure your patients wash their hands with soap and warm water before each test, as contaminates can alter the test result.
* Some meters require test strip calibration coding before use. Be sure to match the code on the meter screen with the test strip vial before use.
* Check the expiration date on the test strips and control solution. The expiration date is located on vial label. Many manufacturers recommend discarding an open vial after 3 months; refer to the instructions that accompany the vial to determine the appropriate discard date.
* Be sure the test strip is fully inserted in the meter and that an adequate blood sample is obtained in order to avoid a false low reading. If your patient has difficulty obtaining an adequate sample, suggest warming the hands first under water and then hang the hand down while gentle squeezing the blood down to the tip of one finger. Avoid excessive squeezing or pinching of the fingertip when obtaining a sample as this can alter test results.
* Some meters provide an option for alternative site testing, such as the palm of the hand or the forearm. Remember, blood glucose can change quickly and these rapid changes are picked up in the finger tips before alternative sites. Teach your patients to only test his or her blood glucose from fingertip sites when experiencing signs or symptoms of hypoglycemia.
* Don't hesitate to question results that are not consistent with physical symptoms.
Finally, to protect yourself and your patients from exposure to bloodborne pathogens, remember to wash your hands and wear gloves before obtaining a blood glucose sample from your patient. You should also follow the manufacturer's recommendation for cleaning the surface of the meter between patients and use disposable, single-use lancing devices. If your patient experiences a serious adverse event that may be associated with glucose monitoring equipment, both patients and healthcare professionals are encouraged to report the event to the manufacturer. If you do not know the manufacturer, report the event to the FDA at https://www.accessdata.fda.gov/scripts/medwatch/index.cfm?action=reporting.home
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