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 .
Prevention of type 2 diabetes - where is the evidence?
Diabetes is an “ old disease ” . The first description of diabetes written on papyrus about 3500 years ago is found in the Ebers papyrus  , which was discovered in Egypt in 1873 by the German archeologist Georg Ebers . Humans , like most mammals , may develop diabetes , if sufficient environmental exposure to physical inactivity , unhealthy diet and obesity are present . Genetic effects are important for the individual risk of type 2 diabetes ( T2D ) but twin studies have shown that the genetic effects combined explain less than 50 % of the risk of T2D ( 1 ) . Today we know almost 100 susceptibility genes associated with T2D but the relative importance of each of these genes is low ( 2 ) , and together they explain only a small part of the disease risk . Thus , genetic screening can not be used for the prediction of T2D for individuals . On the other h and , healthy lifestyle can also prevent T2D in people who are genetically at high risk , e.g. those with positive family history ( 3 ) . Thus , the importance of lifestyle factors for the development and prevention of T2D is overwhelming . The strongest evidence in medicine is considered to come from r and omized controlled trials ( RCTs ) . They are also important in providing the link to causal inference that in most observational studies can not be derived . At the same time , observational studies are necessary for the identification of factors associated with an increased or decreased risk of a disease , and for generation of hypotheses on potential means for prevention based on modifiable risk factors . Observational studies have by now identified a large number of factors that are associated with the development of T2D or with the protection against it . Most of them are related to physical activity , diet and obesity . It has also been shown unequivocally that exposures ( poor nutrition , infections , smoking , etc . ) during fetal life and early infancy result ing in insufficient development ( often shown as low birth weight ) also predict T2D later in life ( 4 ) . Traditionally , T2D has been considered to be a disease of the elderly . However , with increasing obesity and sedentary lifestyle in children , there are increasing numbers of cases of T2D already occurring at a young age in many population s ( 5 ) . In the past two decades several innovative RCTs have repeatedly shown that interventions on modifiable risk factors can reduce the incidence of diabetes in high-risk groups . The evidence has been summarized in several systematic review s and meta-analyses ( 6,7 ) . There is compelling scientific evidence from RCTs that T2D can be prevented or its onset delayed . The key for prevention is a multimodal package of lifestyle changes that is a sum outcome of dietary and physical activity behaviours . The power of lifestyle was dramatically illustrated by the Finnish Diabetes Prevention Study ( DPS ) that explicitly showed that when the study participants with impaired glucose tolerance reached all five modest lifestyle intervention targets , none of them progressed to T2D ( 8) . Importantly , lifestyle intervention lasting for 3–6 years has been shown to have a carry-over effect on T2D incidence that lasts for several years ; up to 15 in the Finnish Diabetes Prevention Study ( 9 ) and 20 years in the China Da Qing Diabetes Prevention Study ( 10 ) . The observed sustained risk reduction seems to be a result of sustained lifestyle changes , but the legacy effect of improved glycaemia during the early intervention may also have contributed to the long-term effect . The follow-up data from the Chinese study indicate moreover that vascular risks are also reduced by lifestyle management . Several prognostic question naires exist for detecting people at risk of T2D ( 11 ) . One of the screening tools with an adequately high sensitivity and specificity is the Finnish Diabetes Risk Score ( FINDRISC ) developed in Finl and ( 12 ) . The FINDRISC has been successfully implemented in the Finnish primary health care system and used also in many other countries . The FINDRISC was also tested in the Omani population and as a result a slightly modified Omani Diabetes Risk Score was developed ( 13 ) which may be a suitable screening tool for the Arab population s in the Middle East . Lifestyle interventions aim ing at translating evidence from efficacy RCTs on T2D prevention into “ real world ” intervention programmes have also been carried out in various population s. Such data were recently combined in a meta- analysis considering the relationship between intervention effectiveness and adherence to guidelines ( 14 ) . The primary meta- analysis included 22 studies with outcome data for weight loss at 12 months . The pooled result of the direct pairwise meta- analysis shows that
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 .