Background
Methods
Inclusion criteria
Data extraction, analysis and reporting
Results
Study | Year | Country | Definition of diabetes as reported | Risk predictors in the model |
---|---|---|---|---|
Aekplakorn et al. [27] | 2006 | Thailand | Diabetes diagnosed according to ADA criteria as FPG level ≥ 126 mg/dL (7.0 mmol/L) or 2-h PG level ≥ 200 mg/dL (11.1 mmol/L) or a previous diagnosis of diabetes | Age, sex, BMI, abdominal obesity (waist circumference), hypertension, family history of diabetes |
Balkau et al. [23] | 2008 | France | Incident cases of diabetes identified by treatment for diabetes or FPG ≥ 7.0 mmol/L | Men: waist circumference, smoking status, hypertension. Women: waist circumference, family history of diabetes, hypertension. |
Chen et al. [28] | 2010 | Australia | Incident diabetes at follow-up defined by treatment with insulin or oral hypoglycaemic agents, FPG level ≥ 7.0 mmol/L, or 2-hPG in OGTT ≥ 11.1 mmol/L | Age, sex, ethnicity, parental history of diabetes, history of high blood glucose, use of antihypertensive medication, smoking status, physical activity, waist circumference |
Chien et al. [29] | 2009 | Taiwan | Diabetes defined by FPG ≥ 7.0 mmol/L or use of oral hypoglycaemic or insulin medication | Age, BMI, WBC count, and triacylglycerol, HDL cholesterol, FPG levels |
Gao et al. [30] | 2009 | Mauritius | Diabetes diagnosed according to 2006 WHO/IDF criteria. Diabetes cases were defined as those who reported a history of diabetes and treatment with glucose-lowering medication and/or FPG ≥ 7.0 mmol/L and/or 2-h PG ≥ 11.1 mmol/L. | Age, sex, BMI, waist circumference, family history of diabetes |
Gupta et al. [40] | 2008 | UK, Ireland, Sweden, Denmark, Iceland, Norway, Finland | FPG ≥ 7 mmol/L or random glucose ≥ 11.1 mmol/L at randomisation or screening visits. Self-reported history of diabetes and drug or dietary therapy for diabetes. Presence of both impaired FPG (> 6 and < 7 mmol/L) and glycosuria at randomisation or screening visits. | Age, sex, FPG, BMI, randomised group, triglycerides, systolic blood pressure, total cholesterol, use of non-coronary artery disease medication, HDL cholesterol, alcohol intake |
Hippisley-Cox et al. [25] | 2009 | UK | Patients with diabetes identified by searching electronic health records for diagnosis Read code for diabetes (C10%) | Age, BMI, family history of diabetes, smoking status, treated hypertension, current treatment with corticosteroids, diagnosis of CVD, social deprivation, ethnicity |
Kahn et al. [31] | 2009 | USA | Participants were considered to have diabetes if they reported a history of physician-diagnosed 'diabetes (sugar in the blood)' or if their FPG level was ≥ 7.0 mmol/L (≥ 126 mg/dL), their non-FPG level was at least 11.1 mmol/L (≥ 200 mg/dL), or their 2-h PG at year 9 follow-up was ≥ 11.1 mmol/L (≥ 200 mg/dL). Additional cases of incident diabetes were identified by criteria-based abstractions of hospital records. | Diabetic mother, diabetic father, hypertension, ethnicity, age, smoking status, waist circumference (sex), height (sex), resting pulse (sex), weight (sex) |
Kolberg et al. [32] | 2009 | Denmark | Diagnosis of type 2 diabetes was defined by 2-h PG ≥ 11.1 mmol/L on OGTT or FPG ≥ 7.0 mmol/L | Adiponectin, C-reactive protein, ferritin, interleukin 2 receptor A, glucose, insulin |
Lindström et al. [33] | 2003 | Finland | Subjects not on antidiabetic drug treatment were diagnosed as having diabetes according to WHO 1999 criteria [12] if they had FPG ≥ 7.0 mmol/L (fasting whole blood glucose ≥ 6.1 mmol/L) and/or 2-h PG ≥ 11.1 mmol/L (2-h whole blood glucose ≥ 10.0 mmol/L) | Age, BMI, waist circumference, use of blood pressure medication, history of high blood glucose, physical activity, daily consumption of vegetables |
Liu et al. [61] | 2011 | China | Diabetes was diagnosed according to ADA criteria as FPG ≥ 126 mg/dL (7.0 mmol/L) or OGTT ≥ 200 mg/dL (11.1 mmol/L). Incident diabetes was ascertained from multiple sources: self-report, FPG and OGTT results, and data on prescribing of hypoglycaemic medication at follow-up survey. | Age, hypertension, history of high blood glucose, BMI, high FPG |
Schmidt et al. [34] | 2005 | USA | Incident diabetes defined by OGTT (FPG ≥ 7.0 mmol/L or a 2-h PG ≥ 11.1 mmol/L) at end of follow-up (1996 to 1998) or as report of clinical diagnosis or treatment for diabetes during follow-up period | Age, ethnicity, parental history of diabetes, FPG, systolic blood pressure, waist circumference, height, HDL cholesterol, triglycerides |
Schulze et al. [35] | 2007 | Germany | Incident diabetes identified through August 2005 by self-reports of diabetes diagnosis, diabetes relevant medication or dietary treatment due to diabetes. All cases were verified by diagnosing physician on basis of ICD-10 criteria. | Waist circumference, height, age, hypertension, intake of red meat, intake of whole-grain bread, coffee consumption, alcohol consumption, physical activity, former smoker, current heavy smoker (≥ 20 cigarettes/day |
Stern et al. [36] | 2002 | USA | Diabetes diagnosed according to WHO criteria (FPG ≥ 7.0 mmol/L (≥ 126 mg/dL) or 2-h PG ≥ 11.1 mmol/L (≥ 200 mg/dL)) [3]. Persons who reported history of diabetes diagnosed by physician and reported current use of insulin or oral antidiabetic agent were considered to have diabetes regardless of plasma glucose level. | Age, sex, ethnicity, FPG, systolic blood pressure, HDL cholesterol, BMI, family history of diabetes |
Sun et al. [37] | 2009 | Taiwan | Not defined | Sex, education level, age, current smoking status, BMI, waist circumference, family history of diabetes, hypertension, FPG |
Tuomilehto et al. [38] | 2010 | Canada, Germany, Austria, Norway, Denmark, Sweden, Finland, Israel, Spain | Primary end point was development of type 2 diabetes, defined as a 2-h PG ≥ 11.1 mmol/L | Acarbose treatment, sex, serum triglyceride level, waist circumference, FPG, height, history of CVD, diagnosed hypertension |
Wilson et al. [39] | 2007 | USA | Participants characterised as developing new diabetes during follow-up if they (1) started receiving oral hypoglycaemic agents or insulin or (2) had a FPG ≥ 126 mg/dL (≥ 7.0 mmol/L) | FPG, BMI, HDL cholesterol, parental history of diabetes, triglyceride level, blood pressure |
Study | Year | Country | Definition of diabetes as reported | Risk predictors in the model |
---|---|---|---|---|
Al Khalaf et al. [60] | 2010 | Kuwait | Diagnosis of diabetes based on ADA 2003 criteria. If FPG was ≥ 7.0 mmol/L or random glucose was ≥ 11.1 mmol/L, participants were classified as having newly diagnosed diabetes. | Age, waist circumference, blood pressure medication, diabetes in sibling |
Al-Lawati et al. [41] | 2007 | Oman | Diabetes was diagnosed according to 1998 WHO criteria for OGTT (FPG 11.1 mmol/l 2-h post 75-g glucose load | Age, waist circumference, BMI, family history of diabetes, hypertension |
Baan et al. [42] | 1999 | The Netherlands | Diabetes defined as use of antidiabetic medication (insulin or oral hypoglycaemic medication) and/or 2-h PG ≥ 11.1 mmol/L according to WHO criteria | Age, sex, use of antihypertensive medication, obesity (BMI ≥ 30) |
Bang et al. [43] | 2009 | USA | Undiagnosed diabetes defined as FPG ≥ 7.0 mmol/L (≥ 126 mg/dL) | Age, sex, family history of diabetes, history of hypertension, obesity (BMI or waist circumference), physical activity |
Borrell et al. [59] | 2007 | USA | FPG ≥ 126 mg/dL | Age, sex, ethnicity, family history of diabetes, self-reported hypertension, hypercholesterolaemia, periodontal disease |
Chaturvedi et al. [44] | 2008 | India | Undiagnosed diabetes defined as those with FPG ≥ 126 mg/dL (≥ 7.0 mmol/L) but who were not aware of their glycaemic status | Age, blood pressure, waist circumference, family history of diabetes |
Gao et al. [45] | 2010 | China | Diabetes defined according to 2006 WHO/IDF criteria. In individuals without known diabetes, undiagnosed diabetes was determined if person had FPG ≥ 7.0 mmol/L and/or postchallenge PG ≥ 11.1 mmol/L | Age, waist circumference, family history of diabetes |
Glümer et al. [46] | 2004 | Denmark | Individuals without known diabetes and with FPG ≥ 7.0 mmol/L or 2-h PG ≥ 11.1 mmol/L defined as having SDM | Age, BMI, sex, known hypertension, physical activity, family history of diabetes |
Keesukphan et al. [47] | 2007 | Thailand | 75-g OGTT carried out as outlined by WHO Diabetes Study Group | Age, BMI, history of hypertension |
Ko et al. [48] | 2010 | Hong Kong | All subjects underwent 75-g OGTT using 1998 WHO criteria (FPG ≥ 7.0 mmol/L and/or 2-h PG ≥ 11.1 mmol/L | Age, sex, BMI, hypertension, dyslipidaemia, family history of diabetes, gestational diabetes |
Mohan et al. [49] | 2005 | India | Diagnosis of diabetes based on WHO Consulting Group criteria, that is, 2-hr PG ≥ 200 mg/dL | Age, abdominal obesity (waist circumference), physical activity, family history of diabetes |
Pires de Sousa et al. [50] | 2009 | Brazil | FPG > 126 mg/dL (7.0 mmol/L), that is, provisional diagnosis of diabetes according to ADA criteria, classified as type 2 diabetes patients | Age, BMI, hypertension |
Ramachandran et al. [51] | 2005 | India | Diabetes diagnosis based on 2-h PG ≥ 11.1 mmol/L | Age, family history of diabetes, BMI, waist circumference, physical activity |
Ruige et al. [52] | 1997 | The Netherlands | Participants underwent 75-g OGTT and were classified according to WHO criteria | Frequent thirst, pain during walking with need to slow down, shortness of breath when walking, age, sex, obesity (BMI), obesity (men), family history of diabetes, use of antihypertensive drugs, reluctance to use bicycle for transportation |
Tabaei and Herman [53] | 2002 | Egypt | Undiagnosed diabetes defined based on FPG ≥ 126 mg/dL and/or 2-h PG ≥ 200 mg/dL | Age, random plasma glucose, postprandial time, sex, BMI |
Study | Year | Country | Model objective (undiagnosed or incident diabetes) | Definition of diabetes as reported | Risk predictors in the model |
---|---|---|---|---|---|
Bindraban et al. [54] | 2008 | The Netherlands | Diagnosed and undiagnosed | FPG ≥ 7.0 mmol/L and/or self-report | Age, BMI, waist circumference, resting heart rate, first-degree relative with diabetes, hypertension, history of CVD, ethnicity |
Cabrera de León et al. [24] | 2008 | Canary Islands | Unclear | Persons recorded as having diabetes if they said they had the disease and reported dietary or pharmacological treatment with oral antidiabetics or insulin. Persons were considered to have undetected type 2 diabetes if they were unaware of disease at time of inclusion in study but had two consecutive FPG values ≥ 7 mmol/L (≥ 126 mg/dL). | Men: age, waist/height ratio, family history of diabetes Women: age, waist/height ratio, family history of diabetes, gestational diabetes |
Gray et al. [58] | 2010 | UK | Undiagnosed and impaired glucose regulation | Participants diagnosed with type 2 diabetes according to WHO criteria [1] with FPG ≥ 7 mmol/L and/or 2-h PG ≥ 11.1 mmol/L. IFG defined as FPG between 6.1 and 6.9 mmol/L inclusive. | Age, ethnicity, sex, first-degree family history of diabetes, antihypertensive therapy or history of hypertension, waist circumference, BMI |
Griffin et al. [55] | 2000 | UK | Diagnosed and undiagnosed | Classified according to WHO criteria | Sex, prescribed antihypertensive medication, prescribed steroids, age, BMI, family history of diabetes, smoking status |
Heikes et al. [56] | 2008 | USA | Undiagnosed and pre-diabetes | Diabetes is defined as FPG ≥ 126 mg/dL and/or 2-h OGTT ≥ 200 mg/dL. Prediabetes defined as IFG and/or IGT without diabetes. Undiagnosed diabetes defined as presence of actual diabetes based on FPG and/or 2-h OGTTand absence of having been told that he or she has diabetes. | Age, waist circumference, history of gestational diabetes, family history of diabetes, ethnicity, high blood pressure, weight, height, parental diabetes, exercise |
Kanaya et al. [57] | 2005 | USA | Abnormal PCPG | Abnormal 2-h PG postchallenge test result (≥ 140 mg/dL) | Sex, age, triglycerides, FPG |
Xie et al. [26] | 2010 | China | Diagnosed and undiagnosed | Participants without a previous diagnosis of diabetes were categorised according to the ADA diagnostic criteria as follows: undiagnosed diabetes (FPG ≥ 7.0 mmol/L) and impaired fasting glycaemia (6.1 to 6.9 mmol/L). Diabetes was defined as self-reported history of diabetes plus undiagnosed diabetes. | Men: waist circumference, age Women: waist/hip ratio, age |
Number of patients and events
Number of risk predictors
Sample size
Treatment of continuous risk predictors
Variables | Data |
---|---|
Sample size, median (IQR) | |
Development cohortb
| 2,562 (1,426 to 4,965) |
Validation cohortsc
| 1,895 (1,253 to 4,398) |
Treatment of continuous risk predictors, n (%) | |
All kept continuous | 13 (30%) |
All categorised/dichotomised | 21 (49%) |
Some categorised, some not | 6 (14%) |
Unclear | 3 (7%) |
Treatment of missing data, n (%) | |
Not mentioned | 16 (41%) |
Complete case | 21 (54%) |
Multiple imputation | 1 (3%) |
Other (for example, surrogate splitter for regression trees) | 1 (3%) |
Model-building strategy, n (%) | |
Stepwise, forward selection, backward elimination | 20 (51%) |
All significant in univariate analysis | 2 (5%) |
Other | 12 (31%) |
Unclear | 5 (13%) |
Overfitting mentioned or discussed, n (%) | 5 (13%) |
Missing data
Model building
Validation
Parameter | Number of studies (%) |
---|---|
Validation | |
Apparent | 30 (77%) |
Internal | 15 (38%) |
Bootstrapping | 2 (5%) |
Jack-knifing | 1 (3%) |
Random split sample | 10 (26%) |
Cross-validation | 2 (5%) |
Temporal | 3 (8%) |
External | 21 (54%) |
Performance metricsb
| |
Discrimination | |
C-statistic | 39 (100%) |
D-statistic | 1 (3%) |
Calibrationc
| 10 (26%) |
Hosmer-Lemeshow statistic | 8 (21%) |
Calibration plot | 2 (5%) |
Classification | |
Reclassification (NRI) | 2 (5%) |
Other (for example, sensitivity, specificity) | 31 (79%) |