The value of glycosylated haemoglobin as a substitute for the oral glucose tolerance test in the detection of impaired glucose tolerance (IGT)

Glucose challenge test screening for prediabetes and early diabetes

AIMS

To test the hypothesis that a 50-g oral glucose challenge test with 1-h glucose measurement would have superior performance compared with other opportunistic screening methods.

METHODS

In this prospective study in a Veterans Health Administration primary care clinic, the following test performances, measured by area under receiver-operating characteristic curves, were compared: 50-g oral glucose challenge test; random glucose; and HbA1c level, using a 75-g oral glucose tolerance test as the 'gold standard'.

RESULTS

The study population was comprised of 1535 people (mean age 56 years, BMI 30.3 kg/m2 , 94% men, 74% black). By oral glucose tolerance test criteria, diabetes was present in 10% and high-risk prediabetes was present in 22% of participants. The plasma glucose challenge test provided area under receiver-operating characteristic curves of 0.85 (95% CI 0.78-0.91) to detect diabetes and 0.76 (95% CI 0.72-0.80) to detect high-risk dysglycaemia (diabetes or high-risk prediabetes), while area under receiver-operating characteristic curves for the capillary glucose challenge test were 0.82 (95% CI 0.75-0.89) and 0.73 (95% CI 0.69-0.77) for diabetes and high-risk dysglycaemia, respectively. Random glucose performed less well [plasma: 0.76 (95% CI 0.69-0.82) and 0.66 (95% CI 0.62-0.71), respectively; capillary: 0.72 (95% CI 0.65-0.80) and 0.64 (95% CI 0.59-0.68), respectively], and HbA1c performed even less well [0.67 (95% CI 0.57-0.76) and 0.63 (95% CI 0.58-0.68), respectively]. The cost of identifying one case of high-risk dysglycaemia with a plasma glucose challenge test would be $42 from a Veterans Health Administration perspective, and $55 from a US Medicare perspective.

CONCLUSIONS

Glucose challenge test screening, followed, if abnormal, by an oral glucose tolerance test, would be convenient and more accurate than other opportunistic tests. Use of glucose challenge test screening could improve management by permitting earlier therapy.

A hospital-based cross-sectional study to develop an estimation formula for 2-h post-challenge plasma glucose for screening impaired glucose tolerance

AIMS

To create and validate an estimation formula for 2-h post-challenge plasma glucose (2-hPG) as an alternative to oral glucose tolerance test (OGTT) for impaired glucose tolerance (IGT) screening.

METHODS

380 Japanese subjects (57.6% males, aged 58.5 (14.0); mean (SD) years) undergoing OGTT were included in this hospital-based cross-sectional study mainly at Kyoto University Hospital between 2000 and 2011. We determined the main predictive variables of 2-hPG from clinical variables and separated the subjects randomly into two groups: a derivation group to construct an estimation formula of 2-hPG on the basis of predictive variables and a validation group to evaluate the accuracy of the formula.

RESULTS

Fasting plasma glucose (FPG) and hemoglobin A1c (HbA1c) were highly correlated with 2-hPG measured by OGTT. Multiple linear regression analysis showed that estimated 2-hPG (e2-hPG) was calculated by the formula: e2-hPG = 1.66 × FPG (mmol/l) + 1.63 × HbA1c (%)-10.11 (R(2), coefficient of determination=60.2%). When the cut-off value was set to the diagnostic criteria of IGT, 7.8 mmol/l of e2-hPG, sensitivity, specificity, and negative predictive value (NPV) were 83.3%, 44.1%, and 74.3%, respectively. When the cut-off value was set lower (7.2 mmol/l), these values were 94.4%, 30.5%, and 85.7%, respectively. The area under the receiver operating characteristic (ROC) curve was 0.68.

CONCLUSIONS

This high-sensitive estimation formula may be a useful alternative to OGTT for IGT screening. For the levels ≤ 7.2 mmol/l, this formula may also be useful in cross-sectional study to identify people whose glucose tolerance is normal.

Impaired glucose tolerance and insulin resistance in heart failure: underrecognized and undertreated?

BACKGROUND

A link between diabetes mellitus (DM) and heart failure (HF) has been well-recognized for more than a century. HF is also closely linked to abnormal glucose regulation (AGR) and insulin resistance (IR) in patients without DM and, similarly, these conditions commonly coexist. In epidemiological studies, each condition appears to predict the other. The prevalence of AGR/IR in HF patients without DM is significantly underrecognized and, as yet, the optimal method for screening for these abnormalities in the outpatient setting is unclear.

METHODS AND RESULTS

The purpose of this review is to overview the prevalence and prognostic impact of AGR and IR in HF patients without DM and discuss potential pathophysiological pathways that link these conditions with HF. The severity of glucose intolerance in patients with HF correlates with functional and clinical severity of HF and is an independent predictor of an adverse outcome. It is thought that changes in cardiac metabolism, including a switch from glucose metabolism toward fatty acid metabolism, may in part contribute to the pathophysiological processes associated with HF patients with AGR/IR.

CONCLUSIONS

We discuss how pharmacological targeting of metabolic pathways in the myocardium of these patients with HF may represent novel therapeutic strategies in these at-risk patients.

Glucose challenge test screening for prediabetes and undiagnosed diabetes

AIMS/HYPOTHESIS

Diabetes prevention and care are limited by lack of screening. We hypothesised that screening could be done with a strategy similar to that used near-universally for gestational diabetes, i.e. a 50 g oral glucose challenge test (GCT) performed at any time of day, regardless of meal status, with one 1 h sample.

METHODS

At a first visit, participants had random plasma and capillary glucose measured, followed by the GCT with plasma and capillary glucose (GCTplasma and GCTcap, respectively). At a second visit, participants had HbA(1c) measured and a diagnostic 75 g OGTT.

RESULTS

The 1,573 participants had mean age of 48 years, BMI 30.3 kg/m(2) and 58% were women and 58% were black. Diabetes (defined by WHO) was present in 4.6% and prediabetes (defined as impaired glucose tolerance [2 h glucose 7.8-11.1 (140-199 mg/dl) with fasting glucose <or=6.9 (125 mg/dl)] and/or impaired fasting glucose with plasma glucose 6.1-6.9 mmol/l [110-125 mg/dl]) in 18.7%. The GCTplasma provided areas under the receiver-operating-characteristic curves of 0.90, 0.82 and 0.79 for detection of diabetes, diabetes or prediabetes, and prediabetes, respectively, all of which were higher than GCTcap, random and capillary glucose, and HbA(1c) (p < 0.02 for all). The performance of GCTplasma was unaffected by time after meals or time of day, and was better in blacks than whites, but otherwise comparable in men and women, and in groups with differing prevalence of glucose intolerance. GCTplasma screening would cost approximately US$84 to identify one person with previously unrecognised diabetes or prediabetes.

CONCLUSIONS/INTERPRETATION

GCT screening for prediabetes and previously unrecognised diabetes would be accurate, convenient and inexpensive. Widespread use of GCT screening could help improve disease management by permitting early initiation of therapy aimed at preventing or delaying the development of diabetes and its complications.

The utility of a single glucometer measurement of fasting capillary blood glucose in the prevalence determination of diabetes mellitus in an urban adult Palestinian population

This paper aims to evaluate the utility of a single glucometer fasting capillary blood glucose (FCBG) measurement in determining the prevalence of diabetes mellitus in a homogeneous adult population. FCBG measurements were compared with results of the oral glucose tolerance test (OGTT) in 445 subjects aged 30-65 years in an urban cross-sectional study in Old Ramallah. Prevalence of diabetes, sensitivity, specificity and predictive values were calculated at different cut-off levels of FCBG, using OGTT as the reference. The prevalence of OGTT-diagnosed diabetes was 2.7%, while it varied considerably using different cut-off levels of FCBG. The sensitivity of a single glucometer (Exac Tech II) measurement of FCBG at the cut-off level of 6.7 mmol 1(-1) was 33.3%, with a specificity of 98.8%. Using the cut-off level of 6.1 mmol 1(-1) as suggested by the 1998 provisional report of a WHO consultation, the sensitivity increased to 41.7%. At a cut-off level of 5.6 mmol 1(-1), a sensitivity of 66.6% was reached, but the specificity decreased slightly. It can be concluded that a single glucometer measurement of FCBG in an adult population is not useful in determining the prevalence of diabetes mellitus.

Haemoglobin A(1c) measurement for diabetes among subjects with a previous history of impaired glucose tolerance

Haemoglobin A(1c) (HbA(1c)) measurement for diagnosis of diabetes and impaired glucose tolerance (IGT) was assessed during a prospective study of subjects with IGT; 183 of the 207 IGT persons underwent the second oral glucose tolerance tests (OGTT) 2.1 years, on the average, after the first tests. HbA(1c) was administered to every participant before the second OGTTs. The results of HbA(1c) were compared with those of the second OGTTs. The sensitivity of HbA(1c) test was 71% for diabetes and 41% for IGT, when the specificity was 93% at a cutoff point of 4.81%. The conclusion is that the HbA(1c) test is moderately sensitive for diabetes but insensitive for IGT, when it is specific. However, it may be useful for selecting and reducing the total number of subjects referred to 2-h OGTTs in a follow-up study of subjects with IGT, if the rate of progression to diabetes is not high.