| Wednesday, February 07, 2018
By Irwin Z. Rothenberg, MBA, MS, CLS(ASCP), Technical Writer /Quality Advisor, COLA Resources, Inc.
Diabetes is a worldwide epidemic. Its prevalence continues to rise globally at an average rate of 8.7 percent, and it currently affects 382 million of the world’s population. Significant increases in populations diagnosed with diabetes have been reported by many nations as their lifestyle and dietary norms evolve with globalization.
The National Diabetes Statistical Report (2014) reported that in the United States alone, diabetes affects 29.1 million people, 8.1 million of whom are as-of-yet undiagnosed and untreated. While people with diabetes make up 9.3 percent of the entire U.S. population, the Centers for Disease Control and Prevention (CDC) estimates that 86 million more people have some level of pre-diabetes, meaning they have blood glucose or hemoglobin A1c levels that are elevated but not yet to the point of diagnosed diabetes. Not everyone with pre-diabetes will develop diabetes; however, an estimated 15 to 30 percent will develop non-insulin dependent or type 2 diabetes within 5 years.
Type 2 diabetes, which used to be called adult-onset diabetes, can affect individuals of all ages, but onset is most often seen in middle-aged and older individuals. The risk for developing disease increases among individuals who are overweight and inactive. Type 2 diabetes usually begins with insulin resistance, when the body needs more insulin to help glucose enter cells. Initially, the beta cells of the pancreas will produce more insulin to manage the added demand. But eventually the pancreas is no longer able to produce sufficient insulin when blood sugar levels increase, such as after meals. At this point, type 2 diabetes has ensued.
Treatment for type 2 diabetes includes use of diabetes medications, dietary changes, and increased physical activity, along with the monitoring and control of blood pressure and lipid levels. An alarming trend across the U.S. is the increasing incidence of type 2 diabetes among individuals < 20 years of age.
The Role of the Laboratory
In today’s preventive care environment, healthcare providers understand that staying ahead of the progression of the disease and associated comorbidities; minimizing the financial implications of disease progression; and improving patient outcomes and quality of life are dependent on the proactive screening for and management of at-risk patients. Laboratory and point-of-care testing (POCT), therefore, play a critical role and bring significant value in the screening, monitoring, and management of diabetes.
Through the power of diagnostic testing, a patient’s chronic condition can be kept in balance and not allowed to escalate to a critical state that lessens quality of life and may require hospitalization and more expensive intervention. Defining diabetes has shifted to the laboratory, as symptoms alone (excessive thirst, frequent urination) are often not adequate for evaluating the presence or the progression of the disease.
Laboratory Test Methodologies
Predominantly, two testing methods are used to diagnose and monitor diabetes: fasting plasma glucose (FPG) and hemoglobin A1c (HbA1c) testing. Both testing methods have their strengths and weaknesses, and proper understanding of the pros and cons of each enables appropriate application of the right test at the right time for better overall diabetes patient management.
Fasting Plasma Glucose
FPG testing measures short-term glucose metabolism, indicating blood glucose levels at a given time. To get an accurate baseline glucose measurement, patients are required to fast at least eight hours prior to the test. Factors that can affect test results include acute illness, stress, and exercise, as well as patients who have not complied with fasting requirements. An FPG of less than 100 mg/dL is considered normal, while a reading above 126 mg/dL puts a patient in the range for diagnosis of diabetes (Table 1).
Random (non-fasting) Plasma Glucose
While not ideal for diabetes diagnosis and management, there is also a place for random (non-fasting) glucose testing in giving physicians and patients quick results regarding the current blood glucose state. It is most appropriate in managing acute episodes (acute hyperglycemia or hypoglycemia). Normal result: 70-125 mg/dl.
The Two- Hour Postprandial Oral Glucose Challenge
Another option is where the blood glucose is measured two hours after a measured dose of glucose is administered orally. The glucose levels are another determinant of potential or existent diabetes.
Introduced in the late 1970s, HbA1c testing offers a measurement of longer-term glucose metabolism. As hemoglobin circulates through the body, glucose in the serum reacts with an amino acid group on hemoglobin in proportion to the amount of glucose in the circulation. This glycated hemoglobin, measured as a percentage of total hemoglobin, thus serves as an indicator of how much glucose is in the blood. A test result >6.5 percent HbA1c indicates diabetes.
Table 1. HbA1c, Fasting Plasma Glucose, and 2 hour Post-prandial glucose level test ranges and Interpretations.
Despite its widespread acceptance and use, HbA1c is not a replacement for FPG testing in managing diabetes. FPG is a measure of short-term glucose levels, while HbA1c is a measure of average long-term glucose levels. Thus, neither is a replacement for the other. Understanding each test, and their potential interferences, ensures proper use and interpretation, which results in more effective patient care.
HbA1c testing considerations
While there are some factors that interfere with FPG testing, interference related to HbA1c testing is more complex. Hemoglobin variants and analytical variables can interfere with HbA1c measurements, as well as the interpretation of results, leading to serious implications for both patients and the clinicians caring for them.
Hemoglobinopathies are genetic variants that affect the structure of a patient’s hemoglobin, which, in turn, can impact an HbA1c test. There are hundreds of types and subtypes of hemoglobinopathies; most of them do not seem to have any physiological consequences nor an effect on HbA1c testing. Others are clinically significant. These include HbS (sickle cell), HbC, HbD, HbE and HbF (elevated fetal hemoglobin).
Hemoglobin variants can cause some HbA1c tests to give false high or low results, leading to treatment that is inadequate or too aggressive. Laboratory personnel should work with physicians to understand patients’ underlying conditions and inform them that results must be interpreted with these factors in mind. For example, offering a report that includes a statement that warns that anemia and thalassemia may affect interpretation, may assist busy physicians in identifying patients who need more careful consideration.
Additionally, lab personnel should be familiar with the patient populations served by their laboratory and the potential genetic variants that may be prevalent in those populations.
Analytical variables relate to factors that interfere with the testing process itself. A test is only as accurate as the sample at the time it was assayed. Some errors are introduced during the handling of the sample, so it is vital for personnel to ensure samples are managed in a way that yields accurate results. An area of particular consideration is sample pre-treatment.
The American Diabetes Association (ADA), the Endocrine Society, and the World Health Organization (WHO) have all endorsed the use of HbA1c for diabetes screening, diagnosis, and management. Recommendations for testing frequency are dependent upon a patient’s condition, compliance level, and risk factors.
Point of Care Testing Enhances the Management of Type 2 Diabetes
The physician’s ability to perform key assays such as HbA1c and fasting plasma glucose in-office is important to establish an effective consultative relationship with diabetic patients and to be able to consider timely therapy modifications to enhance well-being and quality of life. The harmonization and standardization of cost-effective end-to-end solutions across reference labs, hospitals, clinics, and physician offices ensure consistent, accurate, and reliable results regardless of where testing takes place. Point-of-care (POC) testing can maintain control and visibility from a central location to facilitate high-quality results and enhanced patient outcomes.
Diabetes and its complications have become a growing concern for patients, physicians, laboratory personnel, and society as a whole. The diagnosis, screening, monitoring, and treatment of diabetes has been shaped and transformed by the delivery of clinical data through integration of remote near patient testing with larger centralized medical facilities, utilizing advances in data transmission, automation, and test methodologies.
Laboratory professionals are often called upon to take a more active role in helping clinicians understand tests and interpret results; therefore, proper understanding of the strengths and weaknesses of today’s testing methods is imperative for proper disease diagnosis, monitoring and management. Advances in laboratory testing capabilities have led many physicians to rely more heavily on the assistance of laboratory professionals in the clinical interpretation of test results. As future advancements in testing fill the gaps left by today’s technology, clinicians will continue to gain a better view of a patient’s condition, leading to more effective treatment and improved health outcomes.
Irwin Z. Rothenberg is a Technical Writer/Quality Advisor for COLA’s Educational subsidiary, COLA Resources, Inc. (CRI), a leader in online continuing education for physicians, laboratory personnel, and allied health professionals. CRI offers continuing education through online courses, informational products in both electronic and hard copy form, webinars on cutting-edge technology and regulatory issues, and CRI on-site Symposia for Clinical Laboratories, providing live educational sessions and interactive workshops with leading industry organizations. For more information, visit their website at www.criedu.org or call 1-800-981-9883.