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Glucose meter | |
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Purpose | measure concentration of glucose in the blood |
A glucose meter, also referred to as a "glucometer", [1] is a medical device for determining the approximate concentration of glucose in the blood. It can also be a strip of glucose paper dipped into a substance and measured to the glucose chart. It is a key element of glucose testing, including home blood glucose monitoring (HBGM) performed by people with diabetes mellitus or hypoglycemia. A small drop of blood, obtained from slightly piercing a fingertip with a lancet, is placed on a disposable test strip that the meter reads and uses to calculate the blood glucose level. The meter then displays the level in units of mg/dL or mmol/L.
Since approximately 1980, a primary goal of the management of type 1 diabetes and type 2 diabetes mellitus has been achieving closer-to-normal levels of glucose in the blood for as much of the time as possible, guided by HBGM several times a day. The benefits include a reduction in the occurrence rate and severity of long-term complications from hyperglycemia as well as a reduction in the short-term, potentially life-threatening complications of hypoglycemia.
Leland Clark presented his first paper about the oxygen electrode, later named the Clark electrode, on 15 April 1956, at a meeting of the American Society for Artificial Organs during the annual meetings of the Federated Societies for Experimental Biology. [2] [3] In 1962, Clark and Ann Lyons from the Cincinnati Children's Hospital developed the first glucose enzyme electrode. This biosensor was based on a thin layer of glucose oxidase (GOx) on an oxygen electrode. Thus, the readout was the amount of oxygen consumed by GOx during the enzymatic reaction with the substrate glucose. This publication became one of the most often cited papers in life sciences. Due to this work he is considered the “father of biosensors,” especially with respect to the glucose sensing for diabetes patients. [2] [3]
Another early glucose meter was the Ames Reflectance Meter by Anton H. Clemens. It was used in American hospitals in the 1970s. A moving needle indicated the blood glucose after about a minute.
Home glucose monitoring was demonstrated to improve glycemic control of type 1 diabetes in the late 1970s, and the first meters were marketed for home use around 1981. The two models initially dominant in North America in the 1980s were the Glucometer, introduced in November 1981, [4] whose trademark is owned by Bayer, and the Accu-Chek meter (by Roche). Consequently, these brand names have become synonymous with the generic product to many health care professionals. In Britain, a health care professional or a patient may refer to "taking a BM": "Mrs X's BM is 5", etc. BM stands for Boehringer Mannheim, now part of Roche, who produce test strips called 'BM-test' for use in a meter. [5] [6]
In North America, hospitals resisted adoption of meter glucose measurements for inpatient diabetes care for over a decade. Managers of laboratories argued that the superior accuracy of a laboratory glucose measurement outweighed the advantage of immediate availability and made meter glucose measurements unacceptable for inpatient diabetes management. Patients with diabetes and their endocrinologists eventually persuaded acceptance.[ citation needed ] Prior to its discontinuation in July 2021, the YSI 2300 STAT PLUS Glucose and Lactate Analyzer was widely accepted as the de facto standard for reference measurements and system calibration by most manufacturers of glucometers for the past 30 years, despite there being no such regulatory requirement. [7] [8] [9] [10] [11]
Home glucose testing was adopted for type 2 diabetes more slowly than for type 1, and a large proportion of people with type 2 diabetes have never been instructed in home glucose testing. [12] This has mainly come about because health authorities are reluctant to bear the cost of the test strips and lancets.
Test strips that changed color and could be read visually, without a meter, have been widely used since the 1980s. They had the added advantage that they could be cut longitudinally to save money. Critics argued that test strips read by eye are not as accurate or convenient as meter testing. The manufacturer cited studies that show the product is just as effective despite not giving an answer to one decimal place, something they argue is unnecessary for control of blood sugar. This debate also happened in Germany where "Glucoflex-R" was an established strip for type 2 diabetes. As meter accuracy and insurance coverage improved, they lost popularity.
"Glucoflex-R" is Australia manufacturer National Diagnostic Products alternative to the BM test strip. It has versions that can be used either in a meter or read visually. It is also marketed under the brand name Betachek. On May 1, 2009, the UK distributor Ambe Medical Group reduced the price of their "Glucoflex-R" test strip to the NHS, by approximately 50%. This was expected to allow the NHS to save money on strips and perhaps loosen the restrictions on supply a little. Another low cost visually read strip is soon to be available on prescription according to sources at the NHS.[ when? ]
Special glucose meters for multi-patient hospital use are now used. These provide more elaborate quality control records. Their data handling capabilities are designed to transfer glucose results into electronic medical records and the laboratory computer systems for billing purposes.
This section needs additional citations for verification .(November 2010) |
There are several key characteristics of glucose meters which may differ from model to model:
Countries that use mmol/L include Australia, Canada, China, Croatia, Czech Republic, Denmark, Finland, Hong Kong, Hungary, Iceland, Ireland, Jamaica, Kazakhstan, Latvia, Lithuania, Malaysia, Malta, Netherlands, New Zealand, Norway, Russia, Slovakia, Slovenia, South Africa, Sweden, Switzerland, and United Kingdom. [14] [15]
Countries that use mg/dL include Algeria, Argentina, Austria, Bangladesh, Belgium, Brazil, Chile, Columbia, Cyprus, Ecuador, Egypt, France, Georgia, Germany, Greece, India, Indonesia, Iran, Israel, Italy, Japan, Jordan, Korea, Lebanon, Mexico, Peru, Poland, Portugal, South Korea, Spain, Syria, Taiwan, Thailand, Tunisia, Turkey, United Arab Emirates, United States, Uruguay, Venezuela, and Yemen. [14] [15]
The cost of home blood glucose monitoring can be substantial due to the cost of the test strips. In 2006, the US cost to consumers of each glucose strip ranged from about US$0.35 to $1.00. Manufacturers often provide meters at no cost to encourage use of the profitable test strips. Type 1 diabetics may test as often as 4 to 10 times a day due to the dynamics of insulin adjustment, whereas type 2 typically test less frequently, especially when insulin is not part of treatment. In the UK, where the National Health Service (NHS) rather than patients pay for medications including test strips, a 2015 study on the comparative cost-effectiveness of all options for the self-monitoring of blood glucose funded by the NHS uncovered considerable variation in the price charged, which could not be explained by the availability of advanced meter features. It estimated that a total of £12m was invested in providing 42 million self-monitoring blood glucose tests with systems that failed to meet acceptable accuracy standards, and efficiency savings of £23.2m per annum were achievable if the NHS were to disinvest from technologies providing less functionality than available alternatives, but at a much higher price. [18]
Batches of counterfeit test strips for some meters were found in the United States, producing erratic test results that do not meet the legitimate manufacturer's performance specifications. [19]
The search for a successful technique began about 1975 and has continued to the present without a clinically or commercially viable product. [20] As of 1999 [update] , only one such product had ever been approved for sale by the FDA, based on a technique for electrically pulling glucose through intact skin, and it was withdrawn after a short time owing to poor performance and occasional damage to the skin of users. [21]
Continuous glucose monitor systems can consist of a disposable sensor placed under the skin, a transmitter connected to the sensor and a reader that receives and displays the measurements. The sensor can be used for several days before it needs to be replaced. The devices provide real-time measurements, and reduce the need for fingerprick testing of glucose levels. A drawback is that the meters are not as accurate because they read the glucose levels in the interstitial fluid which lags behind the levels in the blood. [22] [23] Continuous blood glucose monitoring systems are also relatively expensive.
Accuracy of glucose meters is a common topic of clinical concern. Blood glucose meters must meet accuracy standards set by the International Organization for Standardization (ISO). According to ISO 15197 Blood glucose meters must provide results that are within ±15% of a laboratory standard for concentrations above 100 mg/dL or within ±15 mg/dL for concentrations below 100 mg/dL at least 95% of the time. [24] However, a variety of factors can affect the accuracy of a test. Factors affecting accuracy of various meters include calibration of meter, ambient temperature, pressure use to wipe off strip (if applicable), size and quality of blood sample, high levels of certain substances (such as ascorbic acid) in blood, hematocrit, dirt on meter, humidity, and aging of test strips. Models vary in their susceptibility to these factors and in their ability to prevent or warn of inaccurate results with error messages. The Clarke Error Grid has been a common way of analyzing and displaying accuracy of readings related to management consequences. More recently an improved version of the Clarke Error Grid has come into use: It is known as the Consensus Error Grid. Older blood glucose meters often need to be "coded" with the lot of test strips used, otherwise, the accuracy of the blood glucose meter may be compromised due to lack of calibration.
Parts of this article (those related to the Future section) need to be updated.(November 2017) |
One noninvasive glucose meter has been approved by the U.S. FDA: The GlucoWatch G2 Biographer made by Cygnus Inc. The device was designed to be worn on the wrist and used electric fields to draw out body fluid for testing. The device did not replace conventional blood glucose monitoring. One limitation was that the GlucoWatch was not able to cope with perspiration at the measurement site. Sweat must be allowed to dry before measurement can resume. Due to this limitation and others, the product is no longer on the market.
The market introduction of noninvasive blood glucose measurement by spectroscopic measurement methods, in the field of near-infrared (NIR), by extracorporal measuring devices, has not been successful because the devices measure tissue sugar in body tissues and not the blood sugar in blood fluid. To determine blood glucose, the measuring beam of infrared light, for example, has to penetrate the tissue for measurement of blood glucose.
There are currently three CGMS (continuous glucose monitoring system) available. The first is Medtronic's Minimed Paradigm RTS with a sub-cutaneous probe attached to a small transmitter (roughly the size of a quarter) that sends interstitial glucose levels to a small pager sized receiver every five minutes. The Dexcom System is another system, available in two different generations in the US, the G4 and the G5. (1Q 2016). It is a hypodermic probe with a small transmitter. The receiver is about the size of a cell phone and can operate up to twenty feet from the transmitter. The Dexcom G4 transmits via radio frequency and requires a dedicated receiver. [25] The G5 version utilizes Bluetooth low energy for data transmission, and can transmit data directly to a compatible cellular telephone. Currently, Apple's iPhone and Android devices can be used as a receiver. [26] Aside from a two-hour calibration period, monitoring is logged at five-minute intervals for up to 1 week. The user can set the high and low glucose alarms. The third CGMS available is the FreeStyle Navigator from Abbott Laboratories.
There is currently an effort to develop an integrated treatment system with a glucose meter, insulin pump, and wristop controller, as well as an effort to integrate the glucose meter and a cell phone. Testing strips are proprietary and available only through the manufacturer (no insurance availability). These "Glugophones" are currently offered in three forms: as a dongle for the iPhone, an add-on pack for LG model UX5000, VX5200, and LX350 cell phones, as well as an add-on pack for the Motorola Razr cell phone. In US, this limits providers to AT&T and Verizon. Similar systems have been tested for a longer time in Finland.[ citation needed ]
Recent advances in cellular data communications technology have enabled the development of glucose meters that directly integrate cellular data transmission capability, enabling the user to both transmit glucose data to the medical caregiver and receive direct guidance from the caregiver on the screen of the glucose meter. The first such device, from Telcare, Inc., was exhibited at the 2010 CTIA International Wireless Expo, [27] where it won an E-Tech award. This device then underwent clinical testing in the US and internationally.
In early 2014 Google reported testing prototypes of contact lenses that monitor glucose levels and alert users when glucose levels cross certain thresholds. [28] [29] [30] Apple has patented methods for determining blood sugar levels by absorption spectroscopy, as well as by analyzing exhaled air in its electronic devices.[ citation needed ]
Many glucose meters employ the oxidation of glucose to gluconolactone catalyzed by glucose oxidase (sometimes known as GOx). Others use a similar reaction catalysed instead by another enzyme, glucose dehydrogenase (GDH). This has the advantage of sensitivity over glucose oxidase but is more susceptible to interfering reactions with other substances. [31]
The first-generation devices relied on the same colorimetric reaction that is still used nowadays in glucose test strips for urine. Besides glucose oxidase, the test kit contains a benzidine derivative, which is oxidized to a blue polymer by the hydrogen peroxide formed in the oxidation reaction. The disadvantage of this method was that the test strip had to be developed after a precise interval (the blood had to be washed away), and the meter needed to be calibrated frequently.
Most glucometers today use an electrochemical method. Test strips contain a capillary that sucks up a reproducible amount of blood. The glucose in the blood reacts with an enzyme electrode containing glucose oxidase (or dehydrogenase). The enzyme is reoxidized with an excess of a mediator reagent, such as a ferricyanide ion, a ferrocene derivative or osmium bipyridyl complex. The mediator in turn is reoxidized by reaction at the electrode, which generates an electric current. In order for the mediator to operate over long timeframes, it needs to be stable in both oxidised and reduced states. This is to allow for continuous regeneration of the oxidised form of the mediator for shuttling of electrons from enzyme to active site. Osmium-based polypyridyl redox complexes and polymers are attractive candidates as mediators due to their stability in oxidised and reduced forms, tunable redox potential, ease of co-immobilisation and ability to operate at low potentials. [32] [33]
The total charge passing through the electrode is proportional to the amount of glucose in the blood that has reacted with the enzyme. The coulometric method is a technique where the total amount of charge generated by the glucose oxidation reaction is measured over a period of time. The amperometric method is used by some meters and measures the electric current generated at a specific point in time by the glucose reaction. This is analogous to throwing a ball and using the speed at which it is travelling at a point in time to estimate how hard it was thrown. The coulometric method can allow for variable test times, whereas the test time on a meter using the amperometric method is always fixed. Both methods give an estimation of the concentration of glucose in the initial blood sample.
The same principle is used in test strips that have been commercialized for the detection of diabetic ketoacidosis (DKA). These test strips use a beta-hydroxybutyrate-dehydrogenase enzyme instead of a glucose oxidizing enzyme and have been used to detect and help treat some of the complications that can result from prolonged hyperglycemia. [34]
Blood alcohol sensors using the same approach, but with alcohol dehydrogenase enzymes, have been tried and patented but have not yet been successfully commercially developed.
This article possibly contains original research .(May 2023) |
Although the apparent value of immediate measurement of blood glucose might seem to be higher for hypoglycemia (low sugar) than hyperglycemia (high sugar), meters have been less useful. The primary problems are precision and ratio of false positive and negative results. An imprecision of ±15% is less of a problem for high glucose levels than low. There is little difference in the management of a glucose of 200 mg/dL compared with 260 (i.e., a "true" glucose of 230±15%), but a ±15% error margin at a low glucose concentration brings greater ambiguity with regards to glucose management.
The imprecision is compounded by the relative likelihoods of false positives and negatives in populations with diabetes and those without. People with type 1 diabetes usually have a wider range of glucose levels, and glucose peaks above normal, often ranging from 40 to 500 mg/dL (2.2 to 28 mmol/L), and when a meter reading of 50 or 70 (2.8 or 3.9 mmol/L) is accompanied by their usual hypoglycemic symptoms, there is little uncertainty about the reading representing a "true positive" and little harm done if it is a "false positive." However, the incidence of hypoglycemia unawareness, hypoglycemia-associated autonomic failure (HAAF) and faulty counterregulatory response to hypoglycemia make the need for greater reliability at low levels particularly urgent in patients with type 1 diabetes mellitus, while this is seldom an issue in the more common form of the disease, type 2 diabetes mellitus.
In contrast, people who do not have diabetes may periodically have hypoglycemic symptoms but may also have a much higher rate of false positives to true, and a meter is not accurate enough to base a diagnosis of hypoglycemia upon. A meter can occasionally be useful in the monitoring of severe types of hypoglycemia (e.g., congenital hyperinsulinism) to ensure that the average glucose when fasting remains above 70 mg/dL (3.9 mmol/L).
Hypoglycemia, also called low blood sugar, is a fall in blood sugar to levels below normal, typically below 70 mg/dL (3.9 mmol/L). Whipple's triad is used to properly identify hypoglycemic episodes. It is defined as blood glucose below 70 mg/dL (3.9 mmol/L), symptoms associated with hypoglycemia, and resolution of symptoms when blood sugar returns to normal. Hypoglycemia may result in headache, tiredness, clumsiness, trouble talking, confusion, fast heart rate, sweating, shakiness, nervousness, hunger, loss of consciousness, seizures, or death. Symptoms typically come on quickly.
The following is a glossary of diabetes which explains terms connected with diabetes.
Blood glucose monitoring is the use of a glucose meter for testing the concentration of glucose in the blood (glycemia). Particularly important in diabetes management, a blood glucose test is typically performed by piercing the skin to draw blood, then applying the blood to a chemically active disposable 'test-strip'. The other main option is continuous glucose monitoring (CGM). Different manufacturers use different technology, but most systems measure an electrical characteristic and use this to determine the glucose level in the blood. Skin-prick methods measure capillary blood glucose, whereas CGM correlates interstitial fluid glucose level to blood glucose level. Measurements may occur after fasting or at random nonfasting intervals, each of which informs diagnosis or monitoring in different ways.
The glucose tolerance test is a medical test in which glucose is given and blood samples taken afterward to determine how quickly it is cleared from the blood. The test is usually used to test for diabetes, insulin resistance, impaired beta cell function, and sometimes reactive hypoglycemia and acromegaly, or rarer disorders of carbohydrate metabolism. In the most commonly performed version of the test, an oral glucose tolerance test (OGTT), a standard dose of glucose is ingested by mouth and blood levels are checked two hours later. Many variations of the GTT have been devised over the years for various purposes, with different standard doses of glucose, different routes of administration, different intervals and durations of sampling, and various substances measured in addition to blood glucose.
Hyperglycemia is a condition in which an excessive amount of glucose circulates in the blood plasma. This is generally a blood sugar level higher than 11.1 mmol/L (200 mg/dL), but symptoms may not start to become noticeable until even higher values such as 13.9–16.7 mmol/L (~250–300 mg/dL). A subject with a consistent fasting blood glucose range between ~5.6 and ~7 mmol/L is considered slightly hyperglycemic, and above 7 mmol/L is generally held to have diabetes. For diabetics, glucose levels that are considered to be too hyperglycemic can vary from person to person, mainly due to the person's renal threshold of glucose and overall glucose tolerance. On average, however, chronic levels above 10–12 mmol/L (180–216 mg/dL) can produce noticeable organ damage over time.
Diabetic coma is a life-threatening but reversible form of coma found in people with diabetes mellitus.
The blood sugar level, blood sugar concentration, blood glucose level, or glycemia is the measure of glucose concentrated in the blood. The body tightly regulates blood glucose levels as a part of metabolic homeostasis.
An insulinoma is a tumour of the pancreas that is derived from beta cells and secretes insulin. It is a rare form of a neuroendocrine tumour. Most insulinomas are benign in that they grow exclusively at their origin within the pancreas, but a minority metastasize. Insulinomas are one of the functional pancreatic neuroendocrine tumour (PNET) group. In the Medical Subject Headings classification, insulinoma is the only subtype of "islet cell adenoma".
Glycated hemoglobin, glycohemoglobin, glycosylated hemoglobin is a form of hemoglobin (Hb) that is chemically linked to a sugar. Several types of glycated hemoglobin measures exist, of which HbA1c, or simply A1c, is a standard single test. Most monosaccharides, including glucose, galactose, and fructose, spontaneously bond with hemoglobin when present in the bloodstream. However, glucose is only 21% as likely to do so as galactose and 13% as likely to do so as fructose, which may explain why glucose is used as the primary metabolic fuel in humans.
Diabetic hypoglycemia is a low blood glucose level occurring in a person with diabetes mellitus. It is one of the most common types of hypoglycemia seen in emergency departments and hospitals. According to the National Electronic Injury Surveillance System-All Injury Program (NEISS-AIP), and based on a sample examined between 2004 and 2005, an estimated 55,819 cases involved insulin, and severe hypoglycemia is likely the single most common event.
Type 1 diabetes (T1D), formerly known as juvenile diabetes, is an autoimmune disease that originates when cells that make insulin are destroyed by the immune system. Insulin is a hormone required for the cells to use blood sugar for energy and it helps regulate glucose levels in the bloodstream. Before treatment this results in high blood sugar levels in the body. The common symptoms of this elevated blood sugar are frequent urination, increased thirst, increased hunger, weight loss, and other serious complications. Additional symptoms may include blurry vision, tiredness, and slow wound healing. Symptoms typically develop over a short period of time, often a matter of weeks if not months.
The term diabetes includes several different metabolic disorders that all, if left untreated, result in abnormally high concentrations of a sugar called glucose in the blood. Diabetes mellitus type 1 results when the pancreas no longer produces significant amounts of the hormone insulin, usually owing to the autoimmune destruction of the insulin-producing beta cells of the pancreas. Diabetes mellitus type 2, in contrast, is now thought to result from autoimmune attacks on the pancreas and/or insulin resistance. The pancreas of a person with type 2 diabetes may be producing normal or even abnormally large amounts of insulin. Other forms of diabetes mellitus, such as the various forms of maturity-onset diabetes of the young, may represent some combination of insufficient insulin production and insulin resistance. Some degree of insulin resistance may also be present in a person with type 1 diabetes.
Many types of glucose tests exist and they can be used to estimate blood sugar levels at a given time or, over a longer period of time, to obtain average levels or to see how fast body is able to normalize changed glucose levels. Eating food for example leads to elevated blood sugar levels. In healthy people, these levels quickly return to normal via increased cellular glucose uptake which is primarily mediated by increase in blood insulin levels.
Fructosamines are compounds that result from glycation reactions between glucose and a primary amine, followed by isomerization via the Amadori rearrangement. Biologically, fructosamines are recognized by fructosamine-3-kinase, which may trigger the degradation of advanced glycation end-products. Fructosamine can also refer to the specific compound 1-amino-1-deoxy-D-fructose (isoglucosamine), first synthesized by Nobel laureate Hermann Emil Fischer in 1886.
An insulin tolerance test (ITT) is a medical diagnostic procedure during which insulin is injected into a patient's vein, after which blood glucose is measured at regular intervals. This procedure is performed to assess pituitary function, adrenal function, insulin sensitivity, and sometimes for other purposes. An ITT is usually ordered and interpreted by an endocrinologist.
A random glucose test, also known as a random blood glucose test or a casual blood glucose test is a glucose test on the blood of a non-fasting person. This test assumes a recent meal and therefore has higher reference values than the fasting blood glucose (FBG) test.
Diabetes mellitus is a disease in which the beta cells of the endocrine pancreas either stop producing insulin or can no longer produce it in enough quantity for the body's needs. The disease can affect humans as well as animals such as dogs.
Neonatal hypoglycemia, also called low blood sugar in newborn babies, occurs when an infant's blood glucose level is less than what is considered normal. There is inconsistency internationally for diagnostic thresholds. In the US, hypoglycemia is when the blood glucose level is below 30 mg/dL within the first 24 hours of life and below 45 mg/dL after, but international standards differ. Age, birth weight, metabolic needs, and wellness state of the newborn has a substantial impact on their blood glucose level. This is a treatable condition, but its treatment depends on the cause of the hypoglycemia. Though it is treatable, it can be fatal if gone undetected. Hypoglycemia is the most common metabolic problem in newborns.
Ambulatory glucose profile (AGP) is a single-page, standardized report for interpreting a patient's daily glucose and insulin patterns. AGP provides both graphic and quantitative characterizations of daily glucose patterns. First developed by Drs. Roger Mazze and David Rodbard, with colleagues at the Albert Einstein College of Medicine in 1987, AGP was initially used for the representation of episodic self-monitored blood glucose (SMBG). The first version included a glucose median and inter-quartile ranges graphed as a 24-hour day. Dr. Mazze brought the original AGP to the International Diabetes Center (IDC) in the late 1980s. Since then, IDC has built the AGP into the internationally recognized standard for glucose pattern reporting.
A continuous glucose monitor (CGM) is a device used for monitoring blood glucose on a continual basis instead of monitoring glucose levels periodically by drawing a drop of blood from a finger. This is known as continuous glucose monitoring. CGMs are used by people who treat their diabetes with insulin, for example people with type 1 diabetes, type 2 diabetes, or other types of diabetes, such as gestational diabetes.