A1C to detect diabetes in healthy adults: when should we recheck?

Prediabetes: A Benign Intermediate Stage or a Risk Factor in Itself?

Prediabetes is a condition when the blood glucose levels are above the normal range but below the threshold for defining diabetes. Previously considered benign, it is now recognized to be associated with various macrovascular and microvascular complications, with increases in the risk of cardiovascular events, nephropathy neuropathy, and retinopathy. Early identification of prediabetics may help detect the risk for these future complications at an earlier stage. Moreover, therapeutic options for prediabetes are available, which can retard its progression to diabetes and the subsequent development of complications. Hence, we make a case for the early identification of prediabetes through screening methods and appropriate institution of management strategies.

Screening for Diabetes and Prediabetes

Overt type 2 diabetes mellitus (T2DM) is preceded by prediabetes and latent diabetes (lasts 9-12 years). Key dysglycemia screening tests are fasting plasma glucose and hemoglobin A1C. Screen-detected T2DM benefits from multifactorial management of cardiovascular risk beyond glycemia. Prediabetes is best addressed by lifestyle modification, with the goal of preventing T2DM. Although there is no trial evidence of prediabetes/T2DM screening effectiveness, simulations suggest that clinic-based opportunistic screening of high-risk individuals is cost-effective. The most rigorous extant recommendations are those of the American Diabetes Association and US Preventive Services Task Force, which advise opportunistic 3-yearly screening.

Screening for Prediabetes and Type 2 Diabetes: US Preventive Services Task Force Recommendation Statement

IMPORTANCE

An estimated 13% of all US adults (18 years or older) have diabetes, and 34.5% meet criteria for prediabetes. The prevalences of prediabetes and diabetes are higher in older adults. Estimates of the risk of progression from prediabetes to diabetes vary widely, perhaps because of differences in the definition of prediabetes or the heterogeneity of prediabetes. Diabetes is the leading cause of kidney failure and new cases of blindness among adults in the US. It is also associated with increased risks of cardiovascular disease, nonalcoholic fatty liver disease, and nonalcoholic steatohepatitis and was estimated to be the seventh leading cause of death in the US in 2017. Screening asymptomatic adults for prediabetes and type 2 diabetes may allow earlier detection, diagnosis, and treatment, with the ultimate goal of improving health outcomes.

OBJECTIVE

To update its 2015 recommendation, the USPSTF commissioned a systematic review to evaluate screening for prediabetes and type 2 diabetes in asymptomatic, nonpregnant adults and preventive interventions for those with prediabetes.

POPULATION

Nonpregnant adults aged 35 to 70 years seen in primary care settings who have overweight or obesity (defined as a body mass index ≥25 and ≥30, respectively) and no symptoms of diabetes.

EVIDENCE ASSESSMENT

The USPSTF concludes with moderate certainty that screening for prediabetes and type 2 diabetes and offering or referring patients with prediabetes to effective preventive interventions has a moderate net benefit.

CONCLUSIONS AND RECOMMENDATION

The USPSTF recommends screening for prediabetes and type 2 diabetes in adults aged 35 to 70 years who have overweight or obesity. Clinicians should offer or refer patients with prediabetes to effective preventive interventions. (B recommendation).

PM2.5 and Diabetes in the Japanese Population

Growing evidence suggests that PM_2.5 is associated with diabetes mellitus (DM). Although DM is a major public health concern, there has not yet been a study of this association in Japan. We used health examination data from 66,885 individuals in Tokyo, Japan 2005–2019. Cox proportional hazards models were used to evaluate an association between annual exposure to PM_2.5 and glycated hemoglobin A_1c (HbA_1c), or fasting plasma glucose (FPG). An increase of 1 μg/m³ in the annual average of PM_2.5 concentration was associated (HR = 1.029; 95% CI = 1.004–1.055) with an increase in diabetes (incident + prevalent). For incident DM, a greater PM_2.5 level was associated with more DM (HR = 1.029; 95% CI, 1.003–1.055). Compared to HbA_1c, FPG showed a stronger association with the annual exposure to PM_2.5 (HR = 1.065; 95% CI, 1.040–1.091). We found that greater exposure to PM_2.5 in the long-term was associated with an increased risk of diabetes, and that the magnitude of association became stronger as the exposure duration increased. Omorogieva Ojo

Development of malignancies and changes in time-dependent hemoglobin A1c among a nondiabetic population: longitudinal analysis

BACKGROUND

The fluctuation of hemoglobin A1c (HbA1c) and changes in health habits over time was not considered in previous studies. The aim of this study was to evaluate the time-sequenced association between malignancy incidence and HbA1c with a longitudinal study design using repeated measurements of HbA1c.

METHODS

A retrospective longitudinal study was conducted at a large teaching hospital in Tokyo, Japan, from 2005 to 2016. All participants who underwent voluntary health check-ups at the hospital were included. Our outcomes were the development of malignancy. We compared these outcomes using HbA1c categories. Longitudinal analyses were conducted with a mixed effects model in which time-dependent HbA1c measurements were applied to consider fluctuations in HbA1c levels, adjusted for covariates.

RESULTS

A total of 77,385 nondiabetic participants were included in the study; the mean age was 44.7 and 49.4% of participants were male. During a median follow-up of 1588 (interquartile range 730-2946) days, 4506 (5.8%) participants developed malignancies. The relationship between future malignancies and HbA1c was U-shaped; both the lower HbA1c groups (OR 1.31, 95% CI 1.17-1.46 for < 5.0%) and the higher HbA1c group (OR 1.87, 95% CI 1.03-3.39 for ≥ 7.5%) had significantly higher odds ratios compared to the 5.5-5.9%. The lowest HbA1c was associated with higher odds of breast cancer (OR 1.5, 95% CI 1.21-1.86) and female genital cancer (OR 1.57, 95% CI 1.04-2.37).

CONCLUSIONS

Our study found a U-shaped association between HbA1c and future malignancies among nondiabetic people but did not find additional risk at the prediabetic level. Low HbA1c may be associated with the incidence of breast cancer and female genital cancer.

5-year versus risk-category-specific screening intervals for cardiovascular disease prevention: a cohort study

BACKGROUND

Clinical guidelines suggest preventive interventions such as statin therapy for individuals with a high estimated 10-year risk of major cardiovascular events. For those with a low or intermediate estimated risk, risk-factor screenings are recommended at 5-year intervals; this interval is based on expert opinion rather than on direct research evidence. Using longitudinal data on the progression of cardiovascular disease risk over time, we compared different screening intervals in terms of timely detection of high-risk individuals, cardiovascular events prevented, and health-care costs.

METHODS

We used data from participants in the British Whitehall II study (aged 40-64 years at baseline) who had repeated biomedical screenings at 5-year intervals and linked these data to electronic health records between baseline (Aug 7, 1991, to May 10, 1993) and June 30, 2015. We estimated participants' 10-year risk of a major cardiovascular event (myocardial infarction, cardiac death, and fatal or non-fatal stroke) using the revised Atherosclerotic Cardiovascular Disease (ASCVD) calculator. We used multistate Markov modelling to estimate optimum screening intervals on the basis of progression rates from low-risk and intermediate-risk categories to the high-risk category (ie, ≥7·5% 10-year risk of a major cardiovascular event). Our assessment criteria included person-years spent in a high-risk category before detection, the number of major cardiovascular events prevented and quality-adjusted life-years (QALYs) gained, and screening costs.

FINDINGS

Of 6964 participants (mean age 50·0 years [SD 6·0] at baseline) with 152 700 person-years of follow-up (mean follow-up 22·0 years [SD 5·0]), 1686 participants progressed to the high-risk category and 617 had a major cardiovascular event. With the 5-year screening intervals, participants spent 7866 (95% CI 7130-8658) person-years unrecognised in the high-risk group. For individuals in the low, intermediate-low, and intermediate-high risk categories, 21 alternative risk category-based screening intervals outperformed the 5-yearly screening protocol. Screening intervals at 7 years, 4 years, and 1 year for those in the low, intermediate-low, and intermediate-high-risk category would reduce the number of person-years spent unrecognised in the high-risk group by 62% (95% CI 57-66; 4894 person-years), reduce the number of major cardiovascular events by 8% (7-9; 49 events), and raise 44 QALYs (40-49) for the study population.

INTERPRETATION

In terms of timely preventive interventions, the 5-year screening intervals were unnecessarily frequent for low-risk individuals and insufficiently frequent for intermediate-risk individuals. Screening intervals based on risk-category-specific progression rates would perform better in terms of preventing major cardiovascular disease events and improving cost-effectiveness.

FUNDING

Medical Research Council, British Heart Association, National Institutes on Aging, NordForsk, Academy of Finland.

HbA1c monitoring interval in patients on treatment for stable type 2 diabetes. A ten-year retrospective, open cohort study

[Aims] This study aims to suggest an informative interval for HbA1c in DM patients with stable glycemic control, based on test characteristics of the HbA1C assay using the signal-to-noise ratio method. [Methods] This was a retrospective, open cohort study. Data were collected between January 2005 to December 2014 at a tertiary-level community hospital in Japan. All adult patients aged under 75 years, with stable glycemic control on a first pharmaceutical regimen for Type II diabetes, and at least two HbA1c measurements after they achieved glycemic stability, were included in the analysis. We defined stable glycemic control as HbA1c <7.0% (52 mmol/mol) and requiring no change in the medication regimen after three consecutive measurements. We adapted a signal-to-noise method for distinguishing true change from measurement error by constructing a linear random effects model to calculate signal and noise for HbA1c. The screening interval for HbA1c was defined as informative when the signal-to-noise ratio exceeded 1. [Results] Among 1066 adults with diabetes, 639 patients (18.5%) were identified as achieving stable glycemic control (511 male (67.3%)), with a mean HbA1c (SD) of 6.4 (0.4)% (46 mmol/mol). Patients with stable glycemic control increase their HbA1c 0.27% (3 mmol/mol) every year while HbA1c has 0.32% (3.5 mmol/mol) noise, as testing characteristics. Signal exceeds noise after 1.2 years (95%CI: 0.9-1.6). [Conclusion] Once patients achieve stable glycemic control at their HbA1c goal, an informative interval for HbA1c monitoring is once every year. Current guidelines, which suggest testing every six months, may contribute to substantial over-testing.

Determining the optimal screening interval for type 2 diabetes mellitus using a risk prediction model

Background

Progression to diabetes mellitus (DM) is variable and the screening time interval not well defined. The American Diabetes Association and US Preventive Services Task Force suggest screening every 3 years, but evidence is limited.

The objective of the study was to develop a model to predict the probability of developing DM and suggest a risk-based screening interval.

Methods

We included non-diabetic adult patients screened for DM in the Cleveland Clinic Health System if they had at least two measurements of glycated hemoglobin (HbA1c), an initial one less than 6.5% (48 mmol/mol) in 2008, and another between January, 2009 and December, 2013. Cox proportional hazards models were created.

The primary outcome was DM defined as HbA1C greater than 6.4% (46 mmol/mol). The optimal rescreening interval was chosen based on the predicted probability of developing DM.

Results

Of 5084 participants, 100 (4.4%) of the 2281 patients with normal HbA1c and 772 (27.5%) of the 2803 patients with prediabetes developed DM within 5 years. Factors associated with developing DM included HbA1c (HR per 0.1 units increase 1.20; 95%CI, 1.13–1.27), family history (HR 1.31; 95%CI, 1.13–1.51), smoking (HR 1.18; 95%CI, 1.03–1.35), triglycerides (HR 1.01; 95%CI, 1.00–1.03), alanine aminotransferase (HR 1.07; 95%CI, 1.03–1.11), body mass index (HR 1.06; 95%CI, 1.01–1.11), age (HR 0.95; 95%CI, 0.91–0.99) and high-density lipoproteins (HR 0.93; 95% CI, 0.90–0.95). Five percent of patients in the highest risk tertile developed DM within 8 months, while it took 35 months for 5% of the middle tertile to develop DM. Only 2.4% percent of the patients in the lowest tertile developed DM within 5 years.

Conclusion

A risk prediction model employing commonly available data can be used to guide screening intervals. Based on equal intervals for equal risk, patients in the highest risk category could be rescreened after 8 months, while those in the intermediate and lowest risk categories could be rescreened after 3 and 5 years respectively.

Diabetes screening intervals based on risk stratification

BACKGROUND

Guidelines for frequency of Type 2 diabetes mellitus (DM) screening remain unclear, with proposed screening intervals typically based on expert opinion. This study aims to demonstrate that HbA1c screening intervals may differ substantially when considering individual risk for diabetes.

METHODS

This was a multi-institutional retrospective open cohort study. Data were collected between April 1999 to March 2014 from one urban and one rural cohort in Japan. After categorization by age, we stratified individuals based on cardiovascular disease risk (Framingham 10-year cardiovascular risk score) and body mass index (BMI). We adapted a signal-to-noise method for distinguishing true HbA1c change from measurement error by constructing a linear random effect model to calculate signal and noise of HbA1c. Screening interval for HbA1c was defined as informative when the signal-to-noise ratio exceeded 1.

RESULTS

Among 96,456 healthy adults, 46,284 (48.0%) were male; age (range) and mean HbA1c (SD) were 48 (30-74) years old and 5.4 (0.4)%, respectively. As risk increased among those 30-44 years old, HbA1c screening intervals for detecting Type 2 DM consistently decreased: from 10.5 (BMI <18.5) to 2.4 (BMI > 30) years, and from 8.0 (Framingham Risk Score <10%) to 2.0 (Framingham Risk Score ≥20%) years. This trend was consistent in other age and risk groups as well; among obese 30-44 year olds, we found substantially shorter intervals compared to other groups.

CONCLUSION

HbA1c screening intervals for identification of DM vary substantially by risk factors. Risk stratification should be applied when deciding an optimal HbA1c screening interval in the general population to minimize overdiagnosis and overtreatment.

The cost-effectiveness of testing strategies for type 2 diabetes: a modelling study

BACKGROUND

An estimated 850,000 people have diabetes without knowing it and as many as 7 million more are at high risk of developing it. Within the NHS Health Checks programme, blood glucose testing can be undertaken using a fasting plasma glucose (FPG) or a glycated haemoglobin (HbA1c) test but the relative cost-effectiveness of these is unknown.

OBJECTIVES

To estimate and compare the cost-effectiveness of screening for type 2 diabetes using a HbA1c test versus a FPG test. In addition, to compare the use of a random capillary glucose (RCG) test versus a non-invasive risk score to prioritise individuals who should undertake a HbA1c or FPG test.

DESIGN

Cost-effectiveness analysis using the Sheffield Type 2 Diabetes Model to model lifetime incidence of complications, costs and health benefits of screening.

SETTING

England; population in the 40-74-years age range eligible for a NHS health check.

DATA SOURCES

The Leicester Ethnic Atherosclerosis and Diabetes Risk (LEADER) data set was used to analyse prevalence and screening outcomes for a multiethnic population. Alternative prevalence rates were obtained from the literature or through personal communication.

METHODS

(1) Modelling of screening pathways to determine the cost per case detected followed by long-term modelling of glucose progression and complications associated with hyperglycaemia; and (2) calculation of the costs and health-related quality of life arising from complications and calculation of overall cost per quality-adjusted life-year (QALY), net monetary benefit and the likelihood of cost-effectiveness.

RESULTS

Based on the LEADER data set from a multiethnic population, the results indicate that screening using a HbA1c test is more cost-effective than using a FPG. For National Institute for Health and Care Excellence (NICE)-recommended screening strategies, HbA1c leads to a cost saving of £12 and a QALY gain of 0.0220 per person when a risk score is used as a prescreen. With no prescreen, the cost saving is £30 with a QALY gain of 0.0224. Probabilistic sensitivity analysis indicates that the likelihood of HbA1c being more cost-effective than FPG is 98% and 95% with and without a risk score, respectively. One-way sensitivity analyses indicate that the results based on prevalence in the LEADER data set are insensitive to a variety of alternative assumptions. However, where a region of the country has a very different joint HbA1c and FPG distribution from the LEADER data set such that a FPG test yields a much higher prevalence of high-risk cases relative to HbA1c, FPG may be more cost-effective. The degree to which the FPG-based prevalence would have to be higher depends very much on the uncertain relative uptake rates of the two tests. Using a risk score such as the Leicester Practice Database Score (LPDS) appears to be more cost-effective than using a RCG test to identify individuals with the highest risk of diabetes who should undergo blood testing.

LIMITATIONS

We did not include rescreening because there was an absence of required relevant evidence.

CONCLUSIONS

Based on the multiethnic LEADER population, among individuals currently attending NHS Health Checks, it is more cost-effective to screen for diabetes using a HbA1c test than using a FPG test. However, in some localities, the prevalence of diabetes and high risk of diabetes may be higher for FPG relative to HbA1c than in the LEADER cohort. In such cases, whether or not it still holds that HbA1c is likely to be more cost-effective than FPG depends on the relative uptake rates for HbA1c and FPG. Use of the LPDS appears to be more cost-effective than a RCG test for prescreening.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Screening for Abnormal Blood Glucose and Type 2 Diabetes Mellitus: U.S. Preventive Services Task Force Recommendation Statement

DESCRIPTION

Update of the 2008 U.S. Preventive Services Task Force (USPSTF) recommendation on screening for diabetes in asymptomatic adults.

METHODS

The USPSTF reviewed the evidence on screening for impaired fasting glucose, impaired glucose tolerance, and type 2 diabetes in asymptomatic, nonpregnant adults who are at average or high risk for diabetes and its complications.

POPULATION

This recommendation applies to adults aged 40 to 70 years seen in primary care settings who do not have symptoms of diabetes and are overweight or obese.

RECOMMENDATION

The USPSTF recommends screening for abnormal blood glucose as part of cardiovascular risk assessment in adults aged 40 to 70 years who are overweight or obese. Clinicians should offer or refer patients with abnormal blood glucose to intensive behavioral counseling interventions to promote a healthful diet and physical activity. (B recommendation).

Monitoring in clinical biochemistry

Monitoring tests form an increasing proportion of the workload in clinical biochemistry and biochemists can help by providing clinicians with information about the variability and precision of tests, the time frame for pharmacodynamic stabilisation after a treatment change, and the frequency of testing. This paper outlines the phases of monitoring, and how to decide if monitoring is beneficial, which test to use for monitoring, when a change in the test result indicates a need for the change in treatment and the length of testing intervals. We conclude with some recommendations for biochemists for future areas of research and advice that can be given to clinicians.

A two-step screening, measurement of HbA1c in association with FPG, may be useful in predicting diabetes

Backgrounds

We compared the usefulness of fasting plasma glucose (FPG), or hemoglobin A1c (HbA1c), or both in predicting type 2 diabetes.

Methods

This retrospective cohort study investigated 9,322 Japanese adults (4,786 men and 4,536 women), aged 19–69 yrs, free of diabetes at baseline. Usefulness was assessed by predictive values (PV), sensitivity, specificity, and the area under the receiver operating characteristic curve (AUROC) maximised under the best cut-off point.

Results

During the average 6 years of follow-up, 221 men (4.6%) and 92 women (2%) developed diabetes. The best cut-off points for FPG (i.e., 5.67 mmol/l for men and 5.5 mmol/l for women) gave excellent AUROC, and the highest positive PV (13% for men and 9% for women) in predicting diabetes. In high risk subjects with FPG 6.1–6.9 mmol/l, 119 men (26.8%) and 39 women (28.3%) developed diabetes. Under the best cut-off points of FPG 6.39 mmol/l and A1c 5.8, AUROC and positive PV for FPG slightly decreased indicating FPG became less useful and were statistically indistinguishable from those for HbA1c in men. In fact, HbA1c was the most useful in women: HbA1c of 6.0% gave the highest positive likelihood ratio of 2.74 and larger AUROC than did FPG. Although AUROC for HbA1c was acceptable and indistinguishable from that for the combined use, HbA1c had higher specificity and positive LR than did the combined use.

Conclusions

This study demonstrated that FPG was the most useful to predict diabetes in the general population. However, in subjects with FPG 6.1–6.9 mmol/l, FPG became less useful and diagnostic performance of FPG was indistinguishable from that of HbA1c in men whereas HbA1c was the most useful in women. Thus, a two-step screening, measurement of HbA1c in association with FPG, may be useful in predicting diabetes.