A comparison of the predictive power for overall blood glucose control of a 'good' fasting level in type 2 diabetic patients on diet alone or with oral agents

Relationship of glycated hemoglobin, and fasting and postprandial hyperglycemia in type 2 diabetes mellitus patients in Malaysia

AIMS/INTRODUCTION

Studies on the relative contributions of fasting and postprandial hyperglycemia (FH and PPH) to glycated hemoglobin (HbA1c ) in patients with type 2 diabetes have yielded inconsistent results. We aimed to assess the relationship by using continuous glucose monitoring in a multi-ethnic cohort.

MATERIALS AND METHODS

A total of 100 adults with type 2 diabetes were assessed with 6-day continuous glucose monitoring and HbA1c . Area under the curve (AUC) ≥5.6 mmol/L was defined as AUCTOTAL . AUC equal to or greater than each preprandial glucose for 4-h duration was defined as AUCPPH . The total PPH (AUCTPPH ) was the sum of the various AUCPPH. The postprandial contribution to overall hyperglycemia was calculated as (AUCTPPH / AUCTOTAL ) × 100%.

RESULTS

The present study comprised of Malay, Indian, and Chinese type 2 diabetes patients at 34, 34 and 28% respectively. Overall, the mean PPH significantly decreased as HbA1c advanced (mixed model repeated measures adjusted, beta-estimate = -3.0, P = 0.009). Age (P = 0.010) and hypoglycemia (P = 0.006) predicted the contribution difference. In oral antidiabetic drug-treated patients (n = 58), FH contribution increased from 54% (HbA1c 6-6.9%) to 67% (HbA1c ≥10%). FH predominance was significant in poorly-controlled groups (P = 0.028 at HbA1c 9-9.9%; P = 0.015 at HbA1c ≥10%). Among insulin users (n = 42), FH predominated when HbA1c was ≥10% before adjustment for hypoglycemia (P = 0.047), whereas PPH was numerically greater when HbA1c was <8%.

CONCLUSIONS

FH and PPH contributions were equal in well-controlled Malaysian type 2 diabetes patients in real-world practice. FH predominated when HbA1c was ≥9 and ≥10% in oral antidiabetic drug- and insulin-treated patients, respectively. A unique observation was the greater PPH contribution when HbA1c was <8% despite the use of basal and mealtime insulin in this multi-ethnic cohort, which required further validation.

The glucose triad and its role in comprehensive glycaemic control: current status, future management

The prevalence of type 2 diabetes across the world has been described as a global pandemic. Despite significant efforts to limit both the increase in the number of cases and the long-term impact on morbidity and mortality, the total number of people with diabetes is projected to continue to rise and most patients still fail to achieve adequate glycaemic control. Optimal management of type 2 diabetes requires an understanding of the relationships between glycosylated haemoglobin (HbA(1c)), fasting plasma glucose and postprandial glucose (the glucose triad), and how these change during development and progression of the disease. Early and sustained control of glycaemia remains important in the management of type 2 diabetes. The contribution of postprandial glucose levels to overall glycaemic control and the role of postprandial glucose targets in disease management are currently debated. However, many patients do not reach HbA(1C) targets set according to published guidelines. As recent data suggest, if driving HbA(1C) down to lower target levels is not the answer, what other factors involved in glucose homeostasis can or should be targeted? Has the time come to change the treatment paradigm to include awareness of the components of the glucose triad, the existence of glucose variability and their potential influence on the choice of pharmacological treatment? It is becomingly increasingly clear that physicians are likely to have to consider plasma glucose levels both after the overnight fast and after meals as well as the variability of glucose levels, in order to achieve optimal glycaemic control for each patient. When antidiabetic therapy is initiated, physicians may need to consider selection of agents that target both fasting and postprandial hyperglycaemia.

Targets and tactics: the relative importance of HbA, fasting and postprandial plasma glucose levels to glycaemic control in type 2 diabetes

BACKGROUND

The incidence of type 2 diabetes is reaching pandemic proportions, impacting patients and healthcare systems across the globe. Evidence suggests that a majority of patients are not achieving recommended blood glucose targets resulting in an increased risk of micro- and macro-vascular complications.

AIM

To review literature on the significance of glycosylated haemoglobin (HbA(1c)), fasting plasma glucose (FPG) and postprandial plasma glucose (PPG), their inter-relationships and relative importance in the treatment of diabetes, and to provide practical guidance on effective monitoring of patients.

METHODS

Clinical guidelines on diabetes management and clinical and preclinical studies of glycaemic control identified through a publications database search were reviewed.

RESULTS

Glycaemic control remains fundamental to the successful management of diabetes. HbA(1c) is the gold standard measure of glycaemic control but recent evidence suggests that postmeal hyperglycaemia also plays an important role in the aetiology of diabetes-associated complications and control of PPG levels is vital to the achievement of recommended HbA(1c) targets.

CONCLUSIONS

The call for action on type 2 diabetes has never been more compelling; with a clear focus on strategies for glycaemic control, the impact of the diabetes pandemic can be limited.

[Contribution of post-breakfast plasma glucose to the glycemic control of type 2 diabetic patients]

Epidemiological studies have documented that postprandial hyperglycemia is the main risk factor for cardiovascular diseases. It has been established that glycated hemoglobin (HbA1C) provides an integrated measure of plasma glucose (PG) of the last 2-3 months. However, the relative contribution of fasting PG (FPG) and postprandial PG (PPG) to the HbA1C value is controversial.

OBJECTIVE

To evaluate FPG and PPG contributions to the HbA1C value in patients with type 2 diabetes mellitus (DM2).

METHODS

53 subjects with stable DM2 were studied. They were treated with oral anti-diabetic agents (n = 27) and/or insulin (n = 26). Each subject went to 3 visits at 2-month-intervals. On each visit, FPG, PPG (2 h after breakfast and lunch), and HbA1C were measured and we provided breakfast and lunch according to their meal habits. PG was measured by glucose-oxidase and HbA1C by ion-exchange chromatography. Statistical analysis was performed by correlation coefficients at a < 0.05 P value.

RESULTS

Correlations were stronger between HbA1C and post-breakfast PG (r: 0.66-0.48), mean FPG (r: 0.64-0.41), glucose area under the curve (r: 0.64-0.46), and mean PPG (r: 0.59-0.41).

CONCLUSIONS

Measurement of post-breakfast PG showed to be another valuable tool for type 2 diabetic glucose control monitoring.

Strongest correlation of HbA(1c) with 1-month-earlier glucose levels in type 2 diabetes

We examined the correlations of hemoglobin A(1c) (HbA(1c)) with each plasma glucose (PG) level obtained at 0 (the same day), 1 and 2 month(s) prior to HbA(1c) determination. Data were from glycemic profiles of four patients of type 2 diabetes mellitus treated with tablets whose HbA(1c) and pre- and post-breakfast PG levels were monitored each month. There was no significant difference in the correlation coefficients in cases 1 and 2, who presented with linear glycemic time courses. In contrast, HbA(1c) correlated with 1-month-earlier pre-breakfast PG level more strongly than 2-month-earlier post-breakfast PG level in cases 3 and 4, and than same-day post-breakfast PG level in case 3 (P<0.05, ANOVA). The cases 3 and 4 presented with fluctuating glycemic time courses. Samples were separated into upslope's and downslope's sections according to HbA(1c) fluctuation in the latter two cases. Reflecting around the 1-month lag between HbA(1c) and PG, the two sections' regression lines for PG versus HbA(1c) corresponded in the only samples related to 1-month-earlier pre- and post-breakfast PG (t-test). In conclusion, it appears that pre- and post-breakfast PG levels are the most reliable predictors of 1-month-later HbA(1c) in type 2 diabetic outpatients who undergo medical examinations every month.

Assessing diabetic control--reliability of methods available in resource poor settings

AIMS AND METHODS

To examine the reliability of random venous or capillary blood glucose testing, random urine glucose testing, and a current symptom history in predicting a high HbA1c in Type 2 diabetic patients taking oral hypoglycaemic agents in a poorly controlled rural African population.

RESULTS

For a cut-off point for HbA1c of > or = 8%, for random venous plasma glucose of > or = 14 mmol/L (present in 47.2% of subjects), specificity was 97.1% (95% CI 85.1-99.9), sensitivity 56.8% (48.8-64.5) and positive predictive value (PPV) 98.9% (94.2-99.9). HbA1c > or = 8% is predicted by a random capillary blood glucose of 17 mmol/L (present in 28.4% of subjects) with specificity 100% (90.0-100.0), PPV 100% (93.7-100.0) and sensitivity of 34.3% (27.2-42.1). HbA1c > or = 8% is predicted by the presence of heavy glycosuria (> or = 55 mmol/L) (present in 35.6%) with specificity 94.1% (80.3-99.3), sensitivity of 41.9% (34.1-49.9) and PPV 97.1% (89.9-99.6). Polyuria/nocturia (present in 31.3%) was the only symptom found to be associated with poor control, with a specificity for predicting HbA1c of > or = 8% of 81.5% (61.9-93.7), PPV 89.1% (76.4-96.4) and sensitivity 30.6% (22.9-39.1).

CONCLUSIONS

Where resources are short, random glucose testing can be used to detect a significant proportion of those with the worst control with a high degree of specificity enabling primary care staff to modify treatment safely. Where facilities are limited capillary blood or urine testing with reagent strips, may be substituted for venous plasma testing in the laboratory. A symptom history was insufficient to replace biochemical testing, but where this is unavailable, urinary symptoms may be helpful.

Can plasma fructosamine substitute for glycated haemoglobin (HbA1c) estimation in the assessment of diabetic control?

The 'gold standard' marker of overall glycaemic control in diabetes mellitus is the level of glycated haemoglobin (HbA1c). It is, however, an expensive and technically difficult assay and is rarely appropriate to tropical laboratories. Plasma fructosamine measurement is cheaper and easier, though it reflects shorter-term glycaemia. We have measured both indices of control in a group of 154 diabetic patients. There was close correlation between the two measurements (r = 0.6506, P < 0.001), but many patients with abnormal HbA1c levels had normal fructosamine levels. This resulted in an assay sensitivity (compared with HbA1c as gold standard) of only 30%, though specificity was 98%. We conclude that fructosamine measurement cannot be regarded as a substitute for HbA1c determination.

Random blood glucose estimation in type 2 diabetes: does it reflect overall glycaemic control?

The relationship between clinic-measured random blood glucose and glycated haemoglobin was investigated in 204 non-insulin-dependent diabetic patients to determine the value of random blood glucose on management decisions in these patients. Treatment was with diet alone in 104 patients (51%: Group 1), and diet and oral hypoglycaemic agents in 100 patients (49%: Group 2). Random blood glucose and glycated haemoglobin were lower in Group 1 than Group 2 (10.9 +/- 4.0 vs 13.0 +/- 4.0 mmol l-1, p < 0.001, and 8.5 (7.8-10.2) vs 9.6 (8.1-11.0)%, p < 0.01, respectively), and there was a positive correlation between random blood glucose and glycated haemoglobin in both groups (rGroup1 = 0.76, and rGroup2 = 0.54, both p < 0.001). In Group 1, 48 (46%) patients had a random blood glucose < 10 mmol l-1 and all but 2 of these had a glycated haemoglobin of < 10%. Thus, random blood glucose < 10 mmol l-1 was 96% sensitive for glycated haemoglobin < 10%. In Group 2 the same sensitivity was 92%. These data suggest that clinic-measured random blood glucose levels below 10.0 mmol l-1 predict acceptable overall glycaemic control in non-insulin-dependent diabetic patients, particularly in those on diet alone. However, a clinic-measured random blood glucose above 10 mmol l-1 was of limited value in predicting glycated haemoglobin values above 10% and a blood glucose cut-off of 14 mmol l-1 appeared more useful. Where resources are limited, clinic random blood glucose estimation may allow clinicians to use glycated haemoglobin measurements more discriminately.