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Diabet Med. 2007 Apr;24(4):333-43. Epub 2007 Mar 15.
-
- Erratum in:
- Diabet Med. 2007 Sep;24(9):1054.
- Comment in:
- Evid Based Med. 2007 Oct;12(5):152.
Department of Public Health, School of Population Health, The University of Melbourne, Australia. c.bennett@unimelb.edu.au
AIM: To assess the validity of glycated haemoglobin A(1c) (HbA(1c)) as a screening tool for early detection of Type 2 diabetes. METHODS: Systematic review of primary cross-sectional studies of the accuracy of HbA(1c) for the detection of Type 2 diabetes using the oral glucose tolerance test as the reference standard and fasting plasma glucose as a comparison. RESULTS Nine studies met the inclusion criteria. At certain cut-off points, HbA(1c) has slightly lower sensitivity than fasting plasma glucose (FPG) in detecting diabetes, but slightly higher specificity. For HbA(1c) at a Diabetes Control and Complications Trial and UK Prospective Diabetes Study comparable cut-off point of > or = 6.1%, the sensitivity ranged from 78 to 81% and specificity 79 to 84%. For FPG at a cut-off point of > or = 6.1 mmol/l, the sensitivity ranged from 48 to 64% and specificity from 94 to 98%. Both HbA(1c) and FPG have low sensitivity for the detection of impaired glucose tolerance (around 50%). CONCLUSIONS HbA(1c) and FPG are equally effective screening tools for the detection of Type 2 diabetes. The HbA(1c) cut-off point of > 6.1% was the recommended optimum cut-off point for HbA(1c) in most reviewed studies; however, there is an argument for population-specific cut-off points as optimum cut-offs vary by ethnic group, age, gender and population prevalence of diabetes. Previous studies have demonstrated that HbA(1c) has less intra-individual variation and better predicts both micro- and macrovascular complications. Although the current cost of HbA(1c) is higher than FPG, the additional benefits in predicting costly preventable clinical complications may make this a cost-effective choice.
PMID: 17367307 [PubMed – indexed for MEDLINE]
Tag: hemoglobina glicosilada
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BMJ 2007;335;879-883
A clinical approach for the diagnosis of diabetes mellitus: an analysis using glycosylated hemoglobin levels
A clinical approach for the diagnosis of diabetes mellitus: an analysis using glycosylated hemoglobin levels
Peters A L, Davidson M B, Schriger D L, Hasselblad V
| Source | JAMA |
|---|---|
| Year published | 1996 |
| Volume | 276(15) |
| Pages | 1246-1252 |
| Record status | This record is a structured abstract written by CRD reviewers. The original has met a set of quality criteria. Since September 1996 abstracts have been sent to authors for comment. Additional factual information is incorporated into the record. Noted as [A:….]. |
| Authors’ objectives | To determine whether a glycosylated haemoglobin (HbA1c) level can be used instead of an oral glucose tolerance test (OGTT) to diagnose diabetes mellitus. |
| Specific interventions included in the review | Studies in which HbA1c levels were measured concurrently with the performance of OGTT in the same person were eligible for inclusion. Only data from patients who had HbA1c levels measured were used in the analysis. Definitions of a positive index test were not reported for the individual included studies. |
| Reference standard test against which the new test was compared | Studies using OGTT, performed concurrently with the index test, as the reference standard were eligible for inclusion. A normal OGTT was defined as a fasting plasma glucose of less than 6.4 mmol/L and a 2-hour post-dextrose value of less than 7.8 mmol/L. Diabetes was defined as a fasting plasma glucose of at least 7.8 mmo/L and a 2-hour post-dextrose value of at least 11.1 mmol/L. Impaired glucose tolerance (IGT) was defined as any condition that was not diabetes or normal. |
| Participants included in the review | Studies of individuals who did not have conditions that would alter glucose tolerance (e.g. pregnancy, cystic fibrosis) were eligible for inclusion. The included studies were of patients with a prior positive screening test result; individuals self- referred from the general population; individuals referred from high-risk populations; and populations purposely enriched with patients known to have diabetes. |
| Outcomes assessed in the review | No a priori inclusion criteria relating to the outcome measures were specified. The review reported the mean HbA1c levels in populations with normal, IGT and diabetic OGTT results. Some estimates of sensitivity, specificity and positive predictive values (assuming a 6% prevalence of diabetes) were reported for a number of HbA1c cutpoints. |
| Study designs of evaluations included in the review | No inclusion criteria relating to study design were specified. |
| What sources were searched to identify primary studies? | MEDLINE was searched from 1966 to 1994 for articles in any language with English abstracts. No search strategy was reported. The references of retrieved articles and the files of one reviewer were checked for further studies. |
| Validity Assessment | The principal investigators of the included studies were contacted for data for the analysis. All available data, published and unpublished, were provided on studies included in the analysis. No process of data checking was described. Three studies for which there was no response from the principal investigator, and 13 for which data could not be obtained, were excluded from the analysis. |
| How were decisions on the relevance of primary studies made? | The principal investigators of potentially relevant studies were contacted. |
| How were the data extracted from primary studies? | Data from the original studies were transferred to a new database by one reviewer and checked against the original data by a second. Patient characteristics, sample size, prevalence of diabetes, details and results of the OGTT, and HbA1c levels were recorded. |
| Number of studies included in the review | Of the 34 studies eligible for inclusion, 31 authors responded when contacted and 18 of these provided relevant information. Therefore, 18 studies (11,276 patients) were initially included. However, because HbA1c showed the least variance in normal individuals, only data from the 8,984 participants (in 10 studies) who had HbA1c levels measured were included. |
| How were the studies combined? | Comparison of OGTT results and HbA1c levels.
Sensitivity, specificity and positive predictive values for HbA1c levels in individuals whose OGTT results met the World Health Organization (WHO) criteria for diabetes were calculated. The positive predictive value was calculated for a hypothetical diabetes prevalence of 6%. Analysis of distribution of HbA1c levels. Bimodal and trimodal models were estimated using pooled data from all 10 studies. The trimodal model was found to be significantly better. Assuming that the first sub-population represents normal, the second undetermined, and the third diabetes, the ability of various HbA1c cutpoints to distinguish between these theoretical sub-populations was investigated. Sensitivity, specificity, and the fraction of the second sub-population defined as having diabetes were calculated. Sensitivity was defined as the probability that someone from the third sub-population has a HbA1c value greater than the cutpoint, while specificity was defined as the probability that someone from the first sub-population has a HbA1c value below the cutpoint. |
| How were differences between studies investigated? | The authors did not report a method for investigating between-study heterogeneity. |
| Results of the review | In those patients whose OGTT result met the criteria for diabetes, the sensitivity, specificity and positive predictive values (assuming a diabetes prevalence of 6%) were: for an HbA1c level of mean HbA1c plus 2 standard deviations (SDs), 66, 98 and 63%, respectively;
for an HbA1c level of mean HbA1c plus 3 SDs, 48, 100 and 90%, respectively; and for an HbA1c level of mean HbA1c plus 4 SDs, 36, 100 and 97%, respectively. The diagnoses of diabetes by HbA1c level and the results of the OGTT were not equivalent. A proposed HbA1c cutpoint of 7% was derived from the trimodal model. Of those patients with an HbA1c level of at least 7%, 89.1% had diabetes, 7.1% had IGT and 3.8% were normal. |
| Was any cost information reported? | No. |
| Authors’ conclusions | An HbA1c level of 7.0% or higher often requires pharmaceutical intervention and is most often associated with the diagnosis of diabetes by WHO standards. An HbA1c level below 7.0% would usually be treated with diet and exercise, regardless of the diagnosis of IGT or diabetes by OGTT. Therefore, the measurement of HbA1c levels may represent a reasonable approach to identifying treatment-requiring diabetes. |
| CRD commentary | The review addressed a clear and relevant question and limited inclusion criteria were defined. The search strategy was limited and it is therefore possible that relevant studies may have been overlooked. In addition, no attempt to identify data from unpublished studies was reported. The principal investigators of all 34 potentially relevant studies were contacted. However, the process of selecting relevant studies and obtaining and checking the data was unclear. From a total of 13,628 participants in the original 34 studies, only 8,984 participants from 10 studies were included in the analysis. This means that approximately one third of the potentially relevant data were not included in the analysis; such a loss of data could potentially have a substantial effect on the findings of the review. The authors’ conclusions, whilst probably valid, make substantial reference to the clinical application of HbA1c levels in practice, an area not addressed by the review. |
| What are the implications of the review? | Practice: The authors stated that to confirm the diagnosis of diabetes, a positive test should be repeated.
Research: The authors did state any implications for further research. |
| Subject index terms status | Subject indexing assigned by NLM |
| Subject index terms | Diabetes-Mellitus/bl [blood] Diabetes-Mellitus/di [diagnosis]; Glucose-Tolerance-Test; Hemoglobin-A,-Glycosylated/an [analysis]; Models,-Biological; Reproducibility-of-Results; Sensitivity-and-Specificity |
| Review funding body | American Diabetes Association. |
| Accession number | 11996008476 |
| Database entry date | 31 January 2005 |
| Language published in | English |
| Address for correspondence | Dr. A L Peters, UCLA Department of Medicine, 200 UCLA Medical Plaza Suite 365, Los Angeles, CA 90095-1693, USA. |
| Link to Pubmed record | 8849753 |
Utility of A1C for diabetes screening in the 1999 2004 NHANES population.
Thirty percent of people with diabetes are undiagnosed (1), and up to 25% already have microvascular complications at diagnosis (2). The American Diabetes Association recommends screening adults 
45 years of age, especially those with a BMI 25 kg/m2, at 3-year intervals with a fasting plasma glucose (FPG) measurement (3). However, physicians infrequently use an FPG for screening. For example, in a large health maintenance organization within the University of Michigan health system, 184 physicians at 22 separate locations screened 5,752 (69%) of 8,286 people without diabetes over a 3-year period. Ninety-five percent of the screening tests were random glucose measurements, 3% were FPGs, and 2% were A1Cs (4). Random glucose levels depend on the length of time after the previous meal and the carbohydrate content of that meal. There is no agreement on what random glucose values should lead to further investigations.
Because A1C levels reflect average glycemia during the preceding 3–4 months, meal issues are not a factor. To determine what A1C level should lead to further tests to diagnose diabetes, we examined the 1999–2004 National Health and Nutrition Examination Survey (NHANES) population of those not known to have diabetes to determine the sensitivity and specificity with which various A1C levels identified people with diabetes.
HbA(1c) as a screening tool for detection of Type 2 diabetes: a systematic review.
- Diabet Med. 2007 Apr;24(4):333-43. Epub 2007 Mar 15.
LinkOut
-
- Erratum in:
- Diabet Med. 2007 Sep;24(9):1054.
- Comment in:
- Evid Based Med. 2007 Oct;12(5):152.
Bennett CM, Guo M , Dharmage SC .
Department of Public Health, School of Population Health, The University of Melbourne, Australia. c.bennett@unimelb.edu.au
AIM: To assess the validity of glycated haemoglobin A(1c) (HbA(1c)) as a screening tool for early detection of Type 2 diabetes. METHODS: Systematic review of primary cross-sectional studies of the accuracy of HbA(1c) for the detection of Type 2 diabetes using the oral glucose tolerance test as the reference standard and fasting plasma glucose as a comparison. RESULTS Nine studies met the inclusion criteria. At certain cut-off points, HbA(1c) has slightly lower sensitivity than fasting plasma glucose (FPG) in detecting diabetes, but slightly higher specificity. For HbA(1c) at a Diabetes Control and Complications Trial and UK Prospective Diabetes Study comparable cut-off point of > or = 6.1%, the sensitivity ranged from 78 to 81% and specificity 79 to 84%. For FPG at a cut-off point of > or = 6.1 mmol/l, the sensitivity ranged from 48 to 64% and specificity from 94 to 98%. Both HbA(1c) and FPG have low sensitivity for the detection of impaired glucose tolerance (around 50%). CONCLUSIONS HbA(1c) and FPG are equally effective screening tools for the detection of Type 2 diabetes. The HbA(1c) cut-off point of > 6.1% was the recommended optimum cut-off point for HbA(1c) in most reviewed studies; however, there is an argument for population-specific cut-off points as optimum cut-offs vary by ethnic group, age, gender and population prevalence of diabetes. Previous studies have demonstrated that HbA(1c) has less intra-individual variation and better predicts both micro- and macrovascular complications. Although the current cost of HbA(1c) is higher than FPG, the additional benefits in predicting costly preventable clinical complications may make this a cost-effective choice.
PMID: 17367307 [PubMed – indexed for MEDLINE]
-
Related Links
- [Diagnostic value of fasting glucose, fructosamine, and glycated haemoglobin HbA(1c) with regard to ADA 1997 and who 1998 criteria for detecting diabetes and other glucose tolerance abnormalities] [Ann Acad Med Stetin. 2004]
- Macrovascular risk and diagnostic criteria for type 2 diabetes: implications for the use of FPG and HbA(1c) for cost-effective screening. [Diabetes Care. 2003]
- The fasting plasma glucose cut-point predicting a diabetic 2-h OGTT glucose level depends on the phenotype. [Diabetes Res Clin Pract. 2002]
- Is fasting blood glucose a reliable parameter for screening for diabetes in hypertension? [Am J Hypertens. 2003]
- Using HbA(1c) to improve efficacy of the american diabetes association fasting plasma glucose criterion in screening for new type 2 diabetes in American Indians: the strong heart study. [Diabetes Care. 2002]
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