Trial ID
Signalling question	Authors' judgement for 'yes'
Study participation (STP) ‐ yes/noa/unclearb/NAc
a. Adequate participation in the study by eligible persons	NA: usually participants with intermediate hyperglycaemia or with no diabetes at baseline are selected from a greater cohort on another research question (e.g. cardiovascular risk factors in elderly people)
b. Description of the source population or population of interest	Source population for cohort with intermediate hyperglycaemia is clearly described
c. Description of the baseline study sample	Number of people with intermediate hyperglycaemia at baseline is clearly described
d. Adequate description of the sampling frame and recruitment	Way of how the source population was established, selection criteria and key characteristics of the source population clearly described
e. Adequate description of the period and place of recruitment	Time period and place of recruitment for both baseline and follow‐up examinations are clearly described
f. Adequate description of inclusion and exclusion criteria	Definiton of people with normoglycaemia, intermediate hyperglycaemia or diabetes mellitus and description of other in‐ and exclusion criteria
STP risk of bias rating (high/low/unclear)	High: majority of items is answered with 'no'; Low: all items answered with 'yes'; Unclear: majority of items is answered with 'unclear Note: potentially a single item may introduce a high risk of bias, depending on study specifics
Study attrition (STA) ‐ yes/no/unclear
a. Adequate response rate for study participants	NA: usually participants with intermediate hyperglycaemia or with no diabetes at baseline are selected from a greater cohort (e.g. all obese people)
b. Description of attempts to collect information on participants who dropped out	Attempts to collect information on participants who dropped out are described (e.g. telephone contact, mail, registers)
c. Reasons for loss to follow‐up are provided	Reasons on participants who dropped out are available (e.g. deceased participants between baseline and follow‐up, participants moving to another location)
d. Adequate description of participants lost to follow‐up	Key elements of participants lost to follow‐up are described (age, sex, glucose status at baseline, body mass index)
e. There are no important differences between participants who completed the study and those who did not	Study authors describe differences between participants completing the study and those who did not as not important or information provided to judge the differences
STA risk of bias rating (high/low/unclear)	High: majority of items is answered with 'no'; Low: all items answered with 'yes'; Unclear: majority of items is answered with 'unclear Note: potentially a single item may introduce a high risk of bias, depending on study specifics
Prognostic factor measurement (PFM) ‐ yes/no/unclear/NA
a. A clear definition or description of the PF is provided	Measurements for intermediate hyperglycaemia are provided (e.g. IFG, IGT, elevated HbA1c)
b. Method of PF measurement is adequately valid and reliable	Ideally measurements for intermediate hyperglycaemia are repeated to ensure diagnosis, single measurements are accepted as well; technique for glucose measurement or HbA1c measurement described
c. Continuous variables are reported or appropriate cut points are used	Standard categories for intermediate hyperglycaemia (FPG 5.6‐6.9 mmol/L (IFG5.6), FPG 6.1‐6.9 mmol/L (IFG6.1), 2‐hr PG 7.8‐<11.0 mmol/L (IGT), HbA1c 6.0‐6.4% (HbA1c6.0), HbA1c 5.7‐6.4% (HbA1c5.7))
d. The method and setting of measurement of PF is the same for all study participants	Measurements of intermediate hyperglycaemia are the same for all study participants
e. Adequate proportion of the study sample has complete data for the PF	NA: usually participants with intermediate hyperglycaemia or with no diabetes at baseline are selected from a greater cohort (e.g. proportion 100% because study focused on IGT‐subcohort)
f. Appropriate methods of imputation are used for missing PF data	NA: missing laboratory measurements for intermediate hyperglycaemia cannot be reliably imputed
PFM risk of bias rating (high/low/unclear)	High: majority of items is answered with 'no'; Low: all items answered with 'yes'; Unclear: majority of items is answered with 'unclear Note: potentially a single item may introduce a high risk of bias, depending on study specifics
Outcome measurement (OM) ‐ yes/no/unclear/NA
a. A clear definition of the outcome is provided	Measurement of type 2 diabetes mellitus has to be defined
b. Method of outcome measurement used is adequately valid and reliable	Measurement of type 2 diabetes mellitus: a glucose (FPG, PG) or HbA1c measurement has to be a part of the diagnosis (self‐reported diabetes alone will not be accepted)
c. The method and setting of outcome measurement is the same for all study participants	Measurements of type 2 diabetes mellitus are the same for all study participants
OM rating (high/low/unclear)	High: majority of items is answered with 'no'; Low: all items answered with 'yes'; Unclear: majority of items is answered with 'unclear Note: potentially a single item may introduce a high risk of bias, depending on study specifics
Study confounding (SC) ‐ yes/no/unclear/NA
a. All important confounders are measured	Important confounders are: age, sex, family history of diabetes, ethnicity, body mass index, blood pressure and hypertension, smoking and drinking status, socioeconomic status, comedications and comorbidities, physical activity
b. Clear definitions of the important confounders measured are provided	Measurement of confounders has to be clearly described
c. Measurement of all important confounders is adequately valid and reliable	Measurement of confounders is valid and reliable
d. The method and setting of confounding measurement are the same for all study participants	Measurements of confounders are the same for all study participants
e. Appropriate methods are used if imputation is used for missing confounder data	Strategy to impute missing confounder data is described
f. Important potential confounders are accounted for in the study design	Methods section of the publication describes strategy to account for confounders
g. Important potential confounders are accounted for in the analysis	Important confounders are accounted for in multivariate logistic regression and Cox proportional hazards models
SC risk of bias rating (high/low/unclear)	High: majority of items is answered with 'no'; Low: all items answered with 'yes'; Unclear: majority of items is answered with 'unclear Note: potentially a single item may introduce a high risk of bias, depending on study specifics
Statistical analysis and reporting (SAR) ‐ yes/no/unclear/NA
a. Sufficient presentation of data to assess the adequacy of the analytic strategy	Mean or median values, including confidence intervals or standard errors or standard deviations
b. Strategy for model building is appropriate and is based on a conceptual framework or model	NA: we do not anticipate conceptual frameworks or explicit model building strategies for this type of research question (focusing on one prognostic factor only)
c. The selected statistical model is adequate for the design of the study	Mainly incidence rates, uni‐ and multivariate logistic regression, Cox proportional hazard model
d. There is no selective reporting of results	NA: development of type 2 diabetes mellitus and potentially regression to normoglycaemia from intermediate hyperglycaemia are the only outcomes; if missing the study will be excluded
SAR risk of bias rating (high/low/unclear)	High: majority of items is answered with 'no'; Low: all items answered with 'yes'; Unclear: majority of items is answered with 'unclear Note: potentially a single item may introduce a high risk of bias, depending on study specifics
aNo: no or no relevant information to answer the signalling question bUnclear: not enough information to answer signalling question with yes or no cNA (not applicable): signalling question not appropriate for this type of prognostic review FPG: fasting plasma glucose; HbA1c: glycosylated haemoglobin A1c; IFG: impaired fasting glucose; IGT: impaired glucose tolerance; PG: post‐load glucose (after an oral glucose tolerance test (OGTT))