Dextrostix are the reagent strips that, by means of a specific enzymatic method, determine the levels of glucose in blood through shades of blue color or colorimetry. In 1963 Ernie Adams invented the Dextrostix strips, which give an approximate value of blood glucose levels and can detect levels between 10mg / dL and 400mg / dL.
The reading and interpretation of the Dextrostix strips is performed by shades of blue, whose intensity, evaluated with the naked eye and compared with a panel of shades, is proportional to the glycemia values. For the more experienced doctors and nurses, the readings and interpretations were considered barely acceptable.
However, for those with less experience the interpretation of the values was influenced by the intensity of the ambient light or by the visual clarity of the operator, and the margin of error was considered quite wide. That is why in 1970 the Ames reflectance meter was invented.
This invention is generated by the need for the most accurate and constant measurement of blood glucose levels for people with a diagnosis of diabetes mellitus. It is a portable and lightweight battery-operated device that measures the light reflected by the test strip and converts it, yielding results in mg of glucose per 100ml.
The invention of the reflectance meter by the Ames company is one of the most valuable advances in medicine, as it allowed patients to measure their blood glucose levels and control their diet and insulin doses, thus reducing emergency visits for hypo and hyperglycemia.
Currently there are hundreds of glucometers that use various techniques for the analysis of the capillary blood sample and give the results in mg / dl or mmol / L. According to the WHO, normal capillary glycemia values are between 70 mg / dL and 110 mg / dL, allowing reaching 125 mg / dL without being considered diabetes mellitus.
Values between 111mg / dL and 125mg / dL reflect some insulin resistance, and although the diagnosis of diabetes has not yet been established, general measures should be monitored and initiated to prevent or delay the onset of diabetes mellitus as far as possible.
Process
It is important to mention that neither the Dextrostix nor the blood to be used for the measurement of glycemia can be refrigerated, since the enzyme that Dextrostix contains (being protein) tends to denature when it is below the temperature of the environment in which it is will use.
Initially, if the situation allows it, the patient and / or family member (if the patient is unconscious) is explained what the intention of the procedure is. The patient is physically and emotionally prepared for the puncture to be performed on the finger to obtain the sample.
Aseptic and antiseptic measures must be performed to later puncture the patient's finger with a lancet, while the finger is squeezed with the other hand to obtain a drop of blood sufficient to perform the test.
Blood covered surface
It must be ensured that the entire area of the Dextrostix strip is covered with blood by using the same finger of the patient to spread the drop of blood evenly over the entire surface of the test strip.
The color of the strip area must be uniform for the correct operation of the reflectance meter's optical lens; that is why the same amount of blood must be contained along the entire surface of the test strip.
Wait time
Wait exactly 60 seconds as measured by a clock, and within the next 2 seconds wash quickly with running water to remove the blood, let it drain a little vertically and dry with a tissue.
Then the test strip must be inserted into the reflectance meter, and in 15 seconds the reading of blood glucose levels in mg / dL is obtained.
Current procedure
The current glucometry procedure is less complicated and cumbersome. After taking the blood sample from the finger pad and placing it in a small compartment that has the test strip, it is inserted into the glucometer and the time indicated according to each manufacturer is waited.
After that time, the capillary glycemia measurement in mg / dL or mmol / L, as the case may be, is displayed on a digital screen.
Dextrostix in neonatology
In neonatology, hypoglycemia is one of the most feared and dangerous pathologies, as it can cause irreversible brain damage in the newborn.
For this reason, the need for a method for the precise, fast and simple measurement of blood glucose levels in neonates is imperative, in order to take appropriate measures if necessary.
Dextrostix has been found to be effective in detecting hypoglycemia, but not as accurate as laboratory methods. According to recent studies in neonates, 90% of the readings made with the Dextrostix strips and with the reflectance meter overestimated the actual values obtained by the glucose oxidase method.
However, it is much faster. An estimated value can be obtained in 3 minutes, while laboratory tests take approximately 1 hour, time that is not available at the time of a hypo or hyperglycemic emergency.
Although it is a useful method in the screening of neonatal hypoglycemia, it is recommended to take measurements in values shown by the strips with the naked eye or by the reflectance meter less than 40 mg / dL due to the overestimation.
References
- I. Drury, EC Sweeney, D. UaConaill. Blood glucose determination by dextrostix / reflectance meter system. December 1972, Volume 141, Issue 1, pp 181–186. Irish Journal of Medical Science. Recovered from: link.springer.com
- World Health Organization. Mellitus diabetes. Diabetes Action Online. Recovered from: who.int
- by Montserrat González García when we have the information. Sensitivity and specificity of a visual refractometer in the rapid diagnosis of hypoglycemia in neonates. Vol. 66, No. 3 May-Jun. 1999 pp 88-91. Mexican Journal of Pediatrics.
- E. Vlok. Manual of nursing. Volume 1. Basic Nursing. 9 th Edition. Recovered from: books.google.pt
- Onyushkina, Ksenia; Nichols, James H. (2009). "Glucose Meters: A Review of Technical Challenges to Obtaining Accurate Results." Journal of diabetes science and technology (Online). 3: 971–980