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Are people with negative diabetes screening tests falsely reassured? Parallel group cohort study embedded in the ADDITION (Cambridge) randomised controlled trial

BMJ 2009; 339 doi: (Published 30 November 2009) Cite this as: BMJ 2009;339:b4535
  1. Charlotte A M Paddison, ESRC postdoctoral research fellow1,
  2. Helen C Eborall, lecturer in social science applied to health2,
  3. Stephen Sutton, professor of behavioural science1,
  4. David P French, professor of health psychology3,
  5. Joana Vasconcelos, reader in medical statistics1,
  6. A Toby Prevost, senior medical statistician4,
  7. Ann-Louise Kinmonth, professor of general practice1,
  8. Simon J Griffin, assistant unit director5
  1. 1General Practice and Primary Care Research Unit, University of Cambridge, Institute of Public Health, Cambridge CB2 0SR
  2. 2Department of Health Sciences, University of Leicester, Leicester LE1 7RH
  3. 3Applied Research Centre in Health and Lifestyle Interventions, Coventry University, Coventry CV1 5FB
  4. 4Department of Public Health Sciences, King’s College London, London SE1 3QD
  5. 5MRC Epidemiology Unit, Institute of Metabolic Science, Addenbrooke’s Hospital, Cambridge CB2 0QQ
  1. Correspondence to: C Paddison camp3{at}


    Objective To assess whether receiving a negative test result at primary care based stepwise diabetes screening results in false reassurance.

    Design Parallel group cohort study embedded in a randomised controlled trial.

    Setting 15 practices (10 screening, 5 control) in the ADDITION (Cambridge) trial.

    Participants 5334 adults (aged 40-69) in the top quarter for risk of having undiagnosed type 2 diabetes (964 controls and 4370 screening attenders).

    Main outcome measures Perceived personal and comparative risk of diabetes, intentions for behavioural change, and self rated health measured after an initial random blood glucose test and at 3-6 and 12-15 months later (equivalent time points for controls).

    Results A linear mixed effects model with control for clustering by practice found no significant differences between controls and people who screened negative for diabetes in perceived personal risk, behavioural intentions, or self rated health after the first appointment or at 3-6 months or 12-15 months later. After the initial test, people who screened negative reported significantly (but slightly) lower perceived comparative risk (mean difference −0.16, 95% confidence interval −0.30 to −0.02; P=0.04) than the control group at the equivalent time point; no differences were evident at 3-6 and 12-15 months.

    Conclusions A negative test result at diabetes screening does not seem to promote false reassurance, whether this is expressed as lower perceived risk, lower intentions for health related behavioural change, or higher self rated health. Implementing a widespread programme of primary care based stepwise screening for type 2 diabetes is unlikely to cause an adverse shift in the population distribution of plasma glucose and cardiovascular risk resulting from an increase in unhealthy behaviours arising from false reassurance among people who screen negative.

    Trial registration Current controlled trials ISRCTN99175498.


    • We are grateful to the patients and the practices for their participation. We thank the Cambridge ADDITION trial coordination team, in particular Kate Williams (trial manager), Nick Wareham (principal investigator), and the MRC field epidemiology team (leads: Susie Hennings and Paul Roberts).

    • Contributors: CAMP, HCE, SRS, and SJG conceived the idea for the paper. HCE coordinated the original study and cleaned the data. CAMP, ATP, and JV analysed the data. CAMP wrote the first draft of the manuscript with HCE, SJG, and SRS. All authors contributed to the final draft. CAMP is the guarantor.

    • Funding: This study was funded by a project grant from the Wellcome Trust (reference number 071200/Z/03/Z). The Cambridge ADDITION trial was funded by the Wellcome Trust (reference number G0000753), the Medical Research Council, and NHS R&D support funding. A-LK and SJG are members of the National Institute for Health Research (NIHR) School for Primary Care Research. SJG receives support from the Department of Health NIHR Programme Grant funding scheme (RP-PG-0606-1259). The General Practice and Primary Care Research Unit is supported by NIHR funds. CAMP is funded by an ESRC postdoctoral fellowship.

    • Competing interests: None declared.

    • Ethical approval: This substudy of the ADDITION (Cambridge) trial was approved by the Eastern MREC. All participants gave written informed consent.

    • Data sharing: Technical appendix, statistical code, and dataset available from corresponding author at camp3{at}

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