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Almost always, a doctor needs laboratory results from a patient’s blood or urine samples to make an accurate diagnosis. These manipulations require a different amount of time: from several minutes to a week. But there are cases when it is impossible to wait or there is no opportunity to use the services of a laboratory, then diagnostic test strips are used. Some rapid tests are designed for home use and provide only approximate results, while others can serve as an adequate alternative to a serious laboratory test.
How did the first rapid tests appear?
It may seem that the idea of diagnostic test strips is the know-how of recent years, but in fact it is a rather old invention. The French chemist Jules Moumene can be considered the creator of the first rapid tests. It was he who in 1850 created the first “strips” for the rapid diagnosis of urine.
Although the process was rather primitive, took much more time than today and evaluated urine only by one indicator, but, as they say, a start was made. Mumene made his test strips from merino wool impregnated with stannous chloride. A drop of urine was to be applied to the “test” and then heated over a candle. If the strip darkened, this indicated the presence of glucose in the urine.
The next important step in the evolution of rapid diagnostics was made in 1900, when Helfenberg AG developed and marketed reagent paper, which served as the basis for a new generation of test strips. At this time, doctors already had the opportunity to quickly check urine for two indicators: protein and glucose. By the 1930s, the quality of diagnostics improved, and it became easier to work with tests. By the mid-40s, using the express method, urine could already be checked for 8 indicators. But the real breakthrough came in the 1950s. It was then that test strips for urine analysis, reminiscent of modern ones, first appeared.
How do they work
Test strips are a method of express diagnostics of urine, blood and other biological fluids for the presence of certain impurities that indicate diseases or for self-monitoring of health status (for example, in diabetes mellitus, diseases of the genitourinary system). Also, with the help of test strips, an increase in excess of the norm of individual indicators in the analysis is detected.
Most modern tests are a plastic or cardboard strip, on some parts of which reagents are applied. The fixative for the reagent, as a rule, is the gel base. After contact of the reagent with a biological fluid (urine, blood), a chemical reaction begins, as a result of which the reagent changes color. A buffer mixture, Griess reagent, organic hydroperoxide, sodium nitroprusside, phosphomolybdic acid, or other substances that change color after contact with a biological fluid can be used as a reagent in an express test.
For example, in tests for the determination of glucose in the urine, the indicator zone contains peroxidase, glucose oxidase, and a redox indicator. If the analyzed urine sample contains glucose, then the indication zone on the test strip will change color. To determine the amount of glucose in a urine sample, you need to compare the color of the indicator on the test with the scale on the package or additional insert. For the accuracy of the result, the comparison should be carried out in good light (preferably in daylight).
In rapid tests, there is always a direct relationship between the hue, color intensity of the reagent and the concentration of certain elements in the biological fluid (protein, glucose, erythrocytes, leukocytes, etc.). Modern test strips can work on two principles: based on the so-called dry chemistry or based on immunochromatographic analysis. The accuracy of the results of the test strips of the latest generation, subject to the rules of operation, reaches 95%.
The leaders in the production of diagnostic test strips are the United States, Canada, Switzerland, Korea and Russia. The most popular are the diagnostic materials from Human-test GmbH, CombiScreen, Combina, Mcral Test.
Types of modern tests
Despite the fact that over the past 60 years, diagnostic test strips have not changed much in appearance, but their functionality, accuracy and quality have improved significantly. New methods of impregnation with test liquid have appeared, color indicators have become more stable, the scale of the color gradient has expanded, which makes it possible to more accurately determine the results of analyzes. Many of the modern test strips are used in medical practice as quite reliable diagnostic tools. Every year, rapid tests are sold in millions of copies around the world.
If the first test strips were intended only for express diagnostics of urine, then in our time the range is much wider. Today, there are a huge number of mono- and polyfunctional tests for the study of urine and blood. For example, the level of glucose and ketone bodies in the urine can be determined either using one multifunctional test, or two monofunctional.
Diagnostic test strips are:
- to determine pregnancy;
- for the presence of drugs in the body;
- detection of various infections, primarily HIV;
- determination of the amount of sugar in the blood;
- to check the level of hemoglobin;
- for the presence of poisons in the body.
Using test strips for urine, you can analyze the content in the body of certain substances and their decay products, determine the amount of protein, glucose, erythrocytes, leukocytes, bilirubin, nitrites, urobilinogen, and control the level of urine acidity. One test can determine from 1 to 12 biochemical parameters. All you need to get the result is to dip the test strip into the urine, wait 1-2 minutes and evaluate the color changes according to the control scale.
As for rapid blood tests, the most popular in the world are diagnostic strips for glucometers. With their help, in a few seconds, 1 drop of blood can determine the exact level of sugar in the bloodstream. Diagnosis of this type is easy to carry out independently at home, and it is also resorted to in a hospital setting and in an ambulance. The advantage of the method is that it requires special skills or medical education, and the procedure can be carried out without assistance.
Diagnostic test strips, working on the principle of an immunochromatographic blood test, help diagnose a patient with myocardial infarction, HIV, the presence of opiates, barbiturates, tricyclic antidepressants, psychotropic and other substances in the body.
Using different types of diagnostic strips, it is possible to determine diseases of the blood, cardiovascular system, kidneys, liver, biliary tract. In addition, with the test strips, diabetics can easily monitor their glucose and ketone levels.
How to use
The accuracy of the results of modern rapid tests is so high that even doctors trust most of them when making a diagnosis. But in order for the strip to give the most accurate result, it is important to follow a few rules during testing. First and most important: it is strictly forbidden to touch the area with the reagent with your hands. The study must be carried out at a temperature not lower than 15 degrees Celsius. Temperature indicators directly affect the quality and speed of the reaction. Failure to follow the rules may result in skewed results.
If the urine for the study was collected in advance and stored in the refrigerator, then it should be warmed to room temperature before the test. Meanwhile, it is worthwhile to understand that it is best to carry out diagnostics immediately after collecting urine, since many substances in its composition decompose (even storage for about 2 hours can distort the result). The test strip should not be left in the urine longer than indicated in the instructions, as this may lead to washing out of the reagent.
Before express blood tests, hands should be washed with soap and water, and the finger should be wiped with alcohol before piercing. To avoid distorting the results, it is recommended to wipe the first drop of blood with a dry sterile cloth or cotton wool, and only then squeeze 1-2 drops of blood onto the test strip.
All types of rapid tests are intended for single use. After the expiration date, they may show false results.
When needed
In medicine, test strips are used when it is necessary to quickly find out the patient’s condition, make a diagnosis, start treatment or gain access to an operation. Sometimes instant determination of biochemical parameters of blood or urine is vital for the patient. For example, if we are talking about the level of sugar in the blood of a diabetic patient. Both hyper- and hypoglycemia cause weakness and malaise, but the treatment in both cases is fundamentally different. With any type of glycemia, it is very important to immediately provide the patient with the necessary assistance, but until the amount of glucose in the bloodstream is determined, nothing can be done. And in such cases, test strips are indispensable.
The method of express diagnostics is most often resorted to by emergency doctors. In addition, test strips can be very helpful when traveling by train or plane, tourists should have them, as well as people working in remote areas or in the field where there is no hospital or clinic nearby.
Often, the method of express diagnostics is resorted to at home. Few of us rush to see a doctor at the first sign of the disease, believing that nothing serious is happening, and the disease will “go away on its own”. And so that the patient understands the seriousness of the situation in time, he can use diagnostic test strips at home.
With the help of diagnostic tests, even people without medical education can determine the presence of a focus of inflammation in the body. For example, if a test shows that bacteria are present in the urine, and white and red blood cell counts are elevated, the person is more likely to have a urinary tract infection. So, you need to immediately rush to the urologist. If the test “found” a lot of red blood cells in the urine, this may indicate urolithiasis, internal trauma, a bleeding neoplasm, such as warts or a polyp, which also requires emergency medical care. After a walk in the cold, do you have frequent urination and lower back pain? A rapid test will help determine the presence of the disease. Test strips can also be very helpful in diagnosing a young child’s condition. If the baby has become restless, constantly crying, then a urine test at home will indicate if there are any health problems with the child.
Test strips can also help out in more piquant situations. Nowadays, venereal diseases are a very common phenomenon. But even if suspicious symptoms appear after sexual intercourse, many do not dare to take tests at the local clinic, and in the meantime the disease (if any) progresses. With the help of diagnostic strips, you can check your health, and if the test indicates a problem, there is nowhere to pull – you must immediately go to a urologist, gynecologist or venereologist. And thanks to the existence of express pregnancy tests, women can find out about their interesting condition at the earliest possible time.
Express diagnostics of urine: decoding
As a rule, with test strips for blood, everything is quite simple. Usually the result is presented in the “positive / negative” format, or is displayed on the screen of a special device (for example, as in glucometers). But deciphering an express urine test can be more difficult. So, what does the color of the indicator on the urine test strip mean?
If the indicator turns brown, this may indicate a high level of glucose in the urine. This happens in diabetics or pregnant women (indicates kidney problems). If the glucose is normal, the indicator area on the test strip will be green.
Burgundy color indicates an increased concentration of ketone bodies. This happens when the body feels a lack of carbohydrates (for example, if a person strictly adheres to a high-protein diet). A normal urine ketone is pink on a test.
The concentration of protein in the analysis in the urine is considered by laboratory technicians as an indicator of kidney function. If the test turned green or even blue, there is reason to suspect the presence of kidney failure. Normally, the reagent zone should be yellow.
In people suffering from urolithiasis, the test strip will indicate increased acidity of urine – the indicator will turn dark green. If the pH of the urine is correct, the reagent zone will remain orange.
Another important characteristic of urine is specific gravity (density). If it is higher than normal, this may indicate kidney disease or indicate that the person was taking drugs or doping drugs. In this case, the reagent will turn from dark blue to mustard.
With increased bilirubin, the indicator will turn from pale pink to a rich, bright pink color. And this can be regarded as a very alarming signal of dysfunction of the liver, gallbladder, or as a sign of hepatitis.
If the rapid test indicated an increase in creatinine, the person may be suffering from kidney failure, dehydration, poor nutrition, or excessive exercise.
Modern diagnostic test strips can tell a lot about a person’s state of health. But do not forget that diagnosis is not a cure. If the test results indicate a health problem, you should immediately make an appointment with a therapist to avoid complications.