HbA1c or glucose for diabetes diagnosis?

Impact of early psychosocial factors (childhood socioeconomic factors and adversities) on future risk of type 2 diabetes, metabolic disturbances and obesity: a systematic review

Background

Psychological factors and socioeconomic status (SES) have a notable impact on health disparities, including type 2 diabetes risk. However, the link between childhood psychosocial factors, such as childhood adversities or parental SES, and metabolic disturbances is less well established. In addition, the lifetime perspective including adult socioeconomic factors remains of further interest.

We carried out a systematic review with the main question if there is evidence in population- or community-based studies that childhood adversities (like neglect, traumata and deprivation) have considerable impact on type 2 diabetes incidence and other metabolic disturbances. Also, parental SES was included in the search as risk factor for both, diabetes and adverse childhood experiences. Finally, we assumed that obesity might be a mediator for the association of childhood adversities with diabetes incidence. Therefore, we carried out a second review on obesity, applying a similar search strategy.

Methods

Two systematic reviews were carried out. Longitudinal, population- or community-based studies were included if they contained data on psychosocial factors in childhood and either diabetes incidence or obesity risk.

Results

We included ten studies comprising a total of 200,381 individuals. Eight out of ten studies indicated that low parental status was associated with type 2 diabetes incidence or the development of metabolic abnormalities. Adjustment for adult SES and obesity tended to attenuate the childhood SES-attributable risk but the association remained. For obesity, eleven studies were included with a total sample size of 70,420 participants. Four out of eleven studies observed an independent association of low childhood SES on the risk for overweight and obesity later in life.

Conclusions

Taken together, there is evidence that childhood SES is associated with type 2 diabetes and obesity in later life. The database on the role of psychological factors such as traumata and childhood adversities for the future risk of type 2 diabetes or obesity is too small to draw conclusions. Thus, more population-based longitudinal studies and international standards to assess psychosocial factors are needed to clarify the mechanisms leading to the observed health disparities.

Glycaemia-independent ethnic differences in HbA(1c) in subjects with impaired glucose tolerance

AIM

To study the ethnic differences in HbA(1c) between Whites and South Asians with impaired glucose tolerance.

METHODS

We audited 75g oral glucose tolerance tests (OGTT) performed in Clinical Chemistry, New Cross Hospital, Wolverhampton over 1 year. HbA(1c) and glycaemia were compared between Whites and South Asians with impaired glucose intolerance (IGT).

RESULTS

There were 46 South Asians (22 female) and 88 Whites (41 female). South Asian subjects were younger (59.2 +/- 14.31 vs. 67.6 +/- 12.63 yrs; P < 0.001) and weighed less (78.1 +/- 17.2 vs. 87.47 +/- 19.1 kgs; P < 0.001) than White subjects. HbA(1c) levels were higher (6.5 +/- 0.7 vs. 6.1 +/- 0.6%; P < 0.001) in South Asians compared to Whites. Fasting glucose (5.71 +/- 0.5 vs. 5.93 +/- 0.7; P = 0.039) was lower in South Asians but 2hour glucose (10.5 +/- 1.0 vs. 10.40 +/- 0.9; P = 0.404) was similar in both ethnic groups.

CONCLUSION

South Asians have higher HbA(1c) levels than Whites despite lower fasting glucose value on OGTT, indicating ethnic differences in HbA(1c) are due to glycaemia-independent factors.

Does HbA1C predict isolated impaired fasting glycaemia in the oral glucose tolerance test in subjects with impaired fasting glycaemia?

Background

To assess the usefulness of erythrocyte glycated haemoglobin (HbA1C) as a screening tool to identify those subjects with impaired fasting glycaemia (IFG) who do not have impaired glucose tolerance (IGT) or diabetes mellitus (DM) on a 75 g oral glucose tolerance test (OGTT).

Design and methods

All subjects undergoing an OGTT had HbA1C measured at baseline. Receiver operator characteristics analysis was used to identify optimal HbA1C cut-off values for diagnosing and excluding IGT and DM.

Results

We studied 140 subjects (69 women) with IFG (fasting capillary plasma glucose between 6.1–6.9 mmol/L). Using World Health Organisation criteria, 27 had isolated IFG, 56 had IGT and 57 had DM. HbA1C was higher ( P < 0.001) in patients with DM (6.8 ± 0.93%) when compared with those with IGT (6.3 ± 0.68%) and isolated IFG (6.2 ± 0.30%), but HbA1C was similar in those with IGT and isolated IFG. There was no HbA1C cut-off value differentiating isolated IFG from IGT or DM. None of the subjects with isolated IFG had HbA1C concentration of >6.8%, but 76% and 54% subjects with IGT and DM, respectively, had HbA1C of ≤6.8%.

Conclusions

HbA1C measurement is of limited value in differentiating isolated IFG, IGT and DM in subjects with IFG. It cannot be used to identify which subjects with IFG do not require an OGTT.

Glycated haemoglobin (HbA1c): today and tomorrow

The assay of glycated haemoglobin (HbA1c) is a gold standard in bioanalysis, and is essential to ensure the optimal care of diabetic patients. Accordingly, the principal scientific societies in diabetology and clinical chemistry have made efforts to standardize this assay in order to select and validate certain analytical methods and achieve consistency in the results obtained therewith. However, clinicians have to be aware of the caution required when interpreting HbA1c assay results owing to modified lifetime and (or) abnormal synthesis of haemoglobin. Although this biological examination has now become an essential part of diabetes monitoring, its status as a screening tool is still controversial, even after 30 years of debate. Other uses of HbA1c assay are currently being assessed in cardiology (coronary syndromes), vascular diseases (arteriopathy), nephrology (renal insufficiency), haematology (anaemia) and oncology (factors of predisposition).