Diagnosis and screening tests for diabetes help doctors detect high blood sugar levels. These tests can diagnose type 1 diabetes, type 2 diabetes, and gestational diabetes. Screening for diabetes is essential because undiagnosed and untreated diabetes leads to chronic hyperglycemia, which damages the eyes, kidneys, nerves, and blood vessels. Diabetes can cause several other health problems, including weight gain, high blood pressure, and heart disease. Learn everything about diagnosis and screening tests for diabetes in this article.
Being proactive in the diagnosis and screening of diabetes is essential for the individual, the health system, and society at large
Types of Diabetes
Diabetes is a chronic (lifelong) disease that causes high blood sugar. The body breaks down food into glucose, which enters the bloodstream and signals the pancreas to produce insulin. Insulin helps glucose get into muscle, fat, and liver cells to be used for energy.
Type 1 diabetes
People with type 1 diabetes don't make enough insulin, so they must inject it daily to stay alive. They must also watch their diet and care for their feet and eyes. If left untreated, people with this condition can develop serious health problems like kidney damage, heart disease, and nerve damage.
Doctors don't know exactly what causes type 1 diabetes, but they believe a combination can cause it. It happens when something triggers the immune system to attack and destroy the insulin-producing cells in the pancreas. These cells are called beta cells, and they help regulate the amount of sugar in the blood. Without these cells, the sugar can't get into the cells and be used for energy, so it builds up in the bloodstream.
Type 2 diabetes
In most cases, people with type 2 diabetes are overweight and don't exercise enough. They're born with genetic traits that make them more susceptible to insulin resistance. Over time, these genes cause their bodies to produce less and less insulin, resulting in high blood sugar.
You can reduce your chances of developing type 2 diabetes by losing weight, eating a healthy diet, exercising regularly, and taking certain medicines if needed. A healthcare team can help you do all these things. They may include your primary care doctor, foot doctor, dentist, eye doctor, registered dietitian, nutritionist, and diabetes educator. Regularly check your blood sugar level.
Gestational diabetes
Gestational diabetes is high blood sugar that develops during pregnancy. It happens when the placenta makes hormones that prevent your body from using insulin to get the sugar it needs for energy.
Most women with gestational diabetes don't have any symptoms. They usually find out they have it during a screening test, such as urine or blood sugar, or when their doctor or midwife checks their belly.
If you have a higher risk of gestational diabetes (such as being overweight before you became pregnant; having a mother, father, or sibling with diabetes; or having had gestational diabetes in a previous pregnancy), you may be tested earlier, such as at your first prenatal visit. Before this test, you'll need to fast (not eat anything) and drink a sweet solution. Then, your doctor will take a sample of your blood before you drink the glucose solution and at one-hour intervals for three hours afterward to see if your blood sugar is too high.
Managing your blood sugar levels with diet, exercise, and, if needed, insulin will help keep you and your baby healthy. People with gestational diabetes should also check their blood sugar often with a home blood glucose monitor.
Diagnostic for Diabetes
The diagnosis of diabetes is based on blood glucose (sugar) levels. There are different tests used to measure your blood sugar level.
Hemoglobin A1c HbA1c Test
The hemoglobin A1c test, also called the glycosylated hemoglobin or HbA1c blood test, measures the average blood sugar level over three months. It does this by calculating how much glucose has bound to hemoglobin molecules. The value gives a good picture of a person's average blood sugar levels and can be used to diagnose diabetes and prediabetes.
The test is usually done by health professionals using a needle to get a sample of blood from a vein or a fingerstick for home testing. A person does not need to fast before the test. Results are given as a percentage. Less than 5.7% indicates a person doesn't have diabetes, while 5.7% to 6.4% signals prediabetes. A 6.5% or higher reading indicates a person has type 2 diabetes.
Some people with a hemoglobin variant may not get an accurate result from the A1C test. These include people of African, Mediterranean, or Southeast Asian descent who carry a hemoglobin C trait and those with sickle cell anemia or thalassemia. People with these conditions should talk to their doctors about what they should do if they are concerned about their A1C results.
Fasting Plasma Glucose FPG Test
This test measures the amount of glucose (sugar) in your blood. It's usually done in the morning after you've fasted for eight hours. This is the most commonly used test to screen for diabetes.
This type of blood sugar test can also be used to diagnose diabetes in people with no signs or symptoms of the disease. In this case, your doctor will compare the results of your FPG test to those of other screening tests.
Your doctor may recommend a lower cut-off value for diagnosing prediabetes, such as 5.3 mmol/L. This would be a more accurate and sensitive test than the 5.6 mmol/L standard cut-off. However, the FPG test is less real than the OGTT. It also can't distinguish between different types of diabetes. In addition, it doesn't measure your blood sugar level after you eat.
Oral Glucose Tolerance Test OGTT
The oral glucose tolerance test (OGTT) measures how well your body processes a type of sugar called glucose. This is a crucial test for the diagnosis of diabetes and gestational diabetes. It is also a standard test to check for prediabetes.
The OGTT involves drinking a solution containing glucose and having your blood tested before and after the drink. This test takes about two hours. It would be best to eat or drink only water for 8 hours before the test. It would help to tell your doctor about illnesses or medications because they may affect the results.
If your results show impaired glucose tolerance or prediabetes, your blood sugar levels are higher than they should be. This increases your risk of developing type 2 diabetes, which can cause serious heart problems. You'll need to do another test to confirm the result. The cost of the OGTT can vary depending on where you get it done and how much your health insurance covers. Independent labs often have lower prices than hospitals and doctor's offices.
Screening Tests for Diabetes
Screening for diabetes is a crucial first step in identifying people who need to be monitored and treated. However, more research is required to determine whether screening for diabetes leads to long-term health benefits.
Several different tests are used to screen for diabetes and prediabetes. Capillary fasting blood glucose and venous plasma glucose are standard screening methods.
Many at-home glucose screening tests are available. However, choosing a test from a company that uses a laboratory accredited by the College of American Pathologists or certified under the Clinical Laboratory Improvement Amendments (CLIA) is crucial. Additionally, the at-home testing device should be FDA-approved for use with blood samples.
There is no randomized trial evidence of benefits from screening for diabetes in asymptomatic individuals. Nevertheless, indirect evidence supports opportunistic screening in patients at high risk. The US Preventive Services Task Force recommends that nonpregnant adults be screened for diabetes by age 45, with rescreening every three years.
Glycated Albumin GA Test
Unlike HbA1c, which requires measuring red blood cells, GA measures the glycation of albumin in the circulation. Due to its shorter lifespan and higher formation rate, GA provides an early indicator of hyperglycemia compared with HbA1c.
Also, since GA is independent of erythrocytes, it may be more robust against conditions affecting erythrocyte lifespan, such as hypo- and hyperthyroidism, liver cirrhosis, massive proteinuria, and hemoglobin variants. However, the sensitivity of GA in these conditions is compromised.
In a recent study, a standardized GA assay traceable to JSCC-recommended standard reference materials demonstrated sufficient precision, linearity, LoB, LoD, and LoQ performance. A formula to report GA in percentage was also derived from 1813 patient samples: %GA = 0.05517 x GA - 0.0300 (r > 0.997). Forest plots showed that GA has moderate accuracy for diagnosing non-GDM.
Random Plasma Glucose RPG Test
RPG collected at an opportunistic screening point, such as a Canadian ED, is an inexpensive and simple tool that can identify many patients with undiagnosed IGM. Using a threshold of over 7 mmol/L, the sensitivity and specificity of RPG for identifying diabetes at one, three, and five-year follow-ups, stratified by age and BMI, was high (S1 Table).
However, as the study was performed at a single site, generalisability to other urban EDs may be limited. Also, examining the impact of time since the last meal on RPG results was impossible. Moreover, the low sensitivity and high false negative rates of RPG and RCG mean that universal screening of pregnant women with either test before 24 weeks gestation is unjustified.
Point-of-care Testing POCT
Point-of-care testing (POCT) is diagnostic testing conducted close to patients, often by clinical personnel outside of the laboratory. POCT can improve clinical efficiency but not substitute central laboratory tests.
Many of the factors that affect central lab results can also affect POCT. POCT devices are often sensitive to vibrations and environmental conditions such as temperature, humidity, and altitude.
Additionally, POCT can be error-prone. Poor phlebotomy and fingerstick techniques, incorrect sample handling, or transportation delays can lead to errors. Clinical operators of POCT equipment may need more formal laboratory training, but even with simple devices, standardized education and training can help to ensure accurate results.
The Bottom Line
Being proactive in the diagnosis and screening of diabetes is essential for the individual, the health system, and society at large. Through it, we can detect, intervene early, manage easily, and improve outcomes for people with diabetes.
