Early diagnosis of diabetes is important, wherever you live in the world. But this is a bigger challenge for some countries than for others
Diabetes – the size of the problem
The diabetes epidemic is one of the biggest problems facing public health globally. Caused by a combination of social, behavioural, uterine and genetic factors, type 2 diabetes mellitus (T2DM) constitutes the vast majority of cases. It is a chronic disease with ~415 million people affected worldwide in 2015 and a projected prevalence of 642 million people by 2040.1
Diabetes is a degenerative, chronic disease, which can result in long-term microvascular and macrovascular complications.2 T2DM is a progressive disease with a complex and multifactorial pathophysiology; as such, each affected person should be evaluated and treated individually.3,4
Early diagnosis is important for successful management of T2DM.
Individuals who do not meet the criteria for diabetes, but who are at high risk of developing T2DM in the future, have an intermediate condition known as prediabetes. People with prediabetes are divided into those with an impaired fasting glucose (IFG) level and those with an impaired glucose tolerance (IGT) level.
The American Diabetes Association (ADA) Expert Committee defines prediabetes as either IFG levels between 100 and 125 mg/dl or IGT with 2 h plasma glucose levels for the oral glucose tolerance test (OGTT) of 140–199 mg/dl.5 The World Health Organization (WHO) uses the range 110–125 mg/dl for IFG for prediabetes.6
Prediabetes is correlated with increased cardiovascular mortality.7,8 However, defining prediabetes with the indicated cut-off values is misleading since lower levels of glucose in the normal range are also correlated with cardiovascular disease in a continuous glycaemic risk spectrum.9
In 2009, the ADA advocated the use of haemoglobin A1c levels (HbA1c) to diagnose diabetes, and recommended the use of an HbA1c of 5.7%–6.4% as being diagnostic of prediabetes.5 Diabetes is diagnosed if a patient has a fasting plasma glucose (FPG) of ≥126 mg/dl, plasma glucose after a 2 h OGTT ≥200 mg/dl, HbA1c ≥6.5% or a random plasma glucose ≥200 mg/dl, as well as symptoms of hyperglycaemia.5
HbA1c: Advantages and disadvantages
The advantages of HbA1c over FPG to diagnose diabetes include:
- Greater clinical convenience – the HbA1c assay doesn’t require patient fasting or tolerance tests
- Pre-analytical stability and decreased biological variation of HbA1c levels
- Stronger correlation of HbA1c with microvascular complications
- Use of HbA1c as a marker for glycaemic control and glycation of proteins, which is the direct link between diagnosis of diabetes and its complications.10
One of the disadvantages of using HbA1c is its unavailability in many parts of the world. It also requires stringent quality assurance tests, and that assays are standardized and aligned to international reference values. Unfortunately, there are different methods that are still used in some parts of the world that do not meet these criteria. In addition, HbA1c test results may be affected by a variety of genetic, haematologic (haemoglobinopathies, certain anaemias and disorders associated with accelerated red blood cell turnover, such as malaria) and illness-related factors.11 A further major disadvantage is the cost and availability of HbA1c assays in some countries.
For both diabetes and prediabetes, it is extremely important for a diagnosis to be determined as early as possible, enabling patients to be treated and thus avoiding or reducing the risk of complications. Since there are differences in tests used in different countries, it is essential to find the most appropriate method for accurate diagnosis.
The situation in Brazil
In Brazil, the prevalence of diabetes is increasing significantly. In the late 1980s, it was estimated that the prevalence of diabetes in the adult population of Brazil was 7.6%.12 More recent data point to this rate being higher, e.g. 13.6% in Triunfo, in the state of Pernambuco.13 And, according to figures from the International Diabetes Federation, in 2015, Brazil had the fourth largest number of people with diabetes worldwide: 14.5 million.1 This is very worrying, since a significant proportion of these individuals will go on to develop chronic complications, resulting in reduced quality of life and life expectancy.
Escalating rates of obesity in all age groups, including adolescents, coupled with general physical inactivity play key roles in insulin resistance and T2DM in Brazil, as in the rest of the world. The disease is generally underdiagnosed in Brazil – healthcare professionals are challenged by lack of adequate resources in health services, uneven distribution of infrastructure throughout the country and poor adherence to advice by patients. There is a need to expand preventative action countrywide, with the Brazilian Diabetic Society guidelines stressing the positive effects of modifying lifestyle to prevent the onset of diabetes.14
2. Nathan DM. Long-term complications of diabetes mellitus. N Engl J Med. 1993;328:1676–1685.
3. UK Prospective Diabetes Study Group. Overview of 6 years therapy of type 2 diabetes: a progressive disease. Diabetes. 1995;44:1249–1258.
4. DeFronzo RA. Banting lecture. From the triumvirate to the ominous octet: a new paradigm for the treatment of type 2 diabetes mellitus. Diabetes. 2009;58:773–795.
5. American Diabetes Association. Diagnosis and classification of diabetes mellitus. Diabetes Care. 2010;33(Suppl 1):S62–S69.
6. World Health Organization. Use of glycated hemoglobin (HbA1c) in the diagnosis of diabetes mellitus. http://www.who.int/diabetes/publications/report-hba1c_2011.pdf?ua=1. Accessed March 18, 2016.
7. Huang Y, Cai X, Chen P, Mai W, Tang H, Huang Y, Hu Y. Associations of prediabetes with all-cause and cardiovascular mortality: a meta-analysis. Ann Med. 2014;46:684–692.
8. Sherwin R, Jastreboff AM. Year in diabetes 2012: The diabetes tsunami. J Clin Endocrinol Metab. 2012;97:4293–4301.
9. Buysschaert M, Bergman M. Definition of prediabetes. Med Clin North Am. 2011;95:289–297, vii.
10. Sacks DB, Arnold M, Bakris GL, Bruns DE, Horvath AR, Kirkman MS, Lernmark A, Metzger BE, Nathan DM. Guidelines and recommendations for laboratory analysis in the diagnosis and management of diabetes mellitus. Clin Chem. 2011;57:e1–e47.
11. World Health Organization. Use of glycated haemoglobin (HbA1c) in the diagnosis of diabetes mellitus. http://www.who.int/diabetes/publications/diagnosis_diabetes2011/en/. Accessed March 18, 2016.
12. Malerbi D, Franco LJ; the Brazilian Cooperative Group on the Study of Diabetes Prevalence. Multicenter study of the prevalence of diabetes mellitus and impaired glucose tolerance in the urban Brazilian population aged 30–69 years. Diabetes Care. 1992;15:1509–16.
13. Lyra R, Silva Rdos S, Montenegro RM Jr, Matos MV, Cézar NJ, Maurício-da-Silva L. Prevalence of diabetes and associated factors in an urban adult population of low educational level and income from the Brazilian Northeast wilderness. Arq Bras Endocrinol Metabol. 2010;54:560–566.
14. de Almeida-Pititto B, Dias ML, Franco de Moraes AC, Ferreira SRG, Franco DR, Eliaschewitz FG. Type 2 diabetes in Brazil: epidemiology and management. Diabetes Metab Syndr Obes. 2015;8:17–28.