Conclusions HbA1c is neither sensitive nor specific for detecting pre‐diabetes ; fasting glucose is specific but not sensitive .
Interventions in people classified through screening as having pre‐diabetes have some efficacy in preventing or delaying onset of type 2 diabetes in trial population s. As screening is inaccurate , many people will receives an incorrect diagnosis and be referred on for interventions while others will be falsely reassured and not offered the intervention .
These findings suggest that “ screen and treat ” policies alone are unlikely to have substantial impact on the worsening epidemic of type 2 diabetes .
& NA ; Objectives To assess diagnostic accuracy of screening tests for  pre‐diabetes  and efficacy of interventions ( lifestyle or metformin ) in preventing onset of type 2 diabetes in people with pre‐diabetes .
The appraisal of public health interventions: the use of theory.
BACKGROUND Public health decision-making is hampered by inappropriate adherence to underpowered r and omized controlled trials ( RCTs ) which give inconclusive results and lead to decision-makers being loath to recommend interventions with strong theoretical and observational support . METHODS We outline situations in which robust decisions about health interventions can be made without trial evidence . We present a new approach in which theory , causal models and past observations are given proper regard in the decision-making process . RESULTS Using our approach , we provide examples where the use of causal theories and observations in areas , such as salt reduction , smoking cessation and gardening to improve mental health , is sufficient for deciding that such interventions are effective for improving health without needing the support of underpowered RCTs . Particularly where RCT evidence is inconclusive , our approach may provide similar aggregate health outcomes for society for vastly lower cost . CONCLUSIONS When knowledge and theoretical underst and ing are unable sufficiently to reduce doubt about the direction of effect from an intervention , decisions should be made using evidence -based medicine approaches . There are , however , many cases where the combination of robust theory , causal underst and ing and observation are able to provide sufficient evidence of the direction of effect from an intervention that current practice should be altered
Conclusions HbA1c is neither sensitive nor specific for detecting pre‐diabetes ; fasting glucose is specific but not sensitive .
Interventions in people classified through screening as having pre‐diabetes have some efficacy in preventing or delaying onset of type 2 diabetes in trial population s. As screening is inaccurate , many people will receives an incorrect diagnosis and be referred on for interventions while others will be falsely reassured and not offered the intervention .
These findings suggest that “ screen and treat ” policies alone are unlikely to have substantial impact on the worsening epidemic of type 2 diabetes .
& NA ; Objectives To assess diagnostic accuracy of screening tests for  pre‐diabetes  and efficacy of interventions ( lifestyle or metformin ) in preventing onset of type 2 diabetes in people with pre‐diabetes .