BackgroundInsulin is generally administered to people with type 1 diabetes mellitus (T1DM) using multiple daily injections (MDIs), but can also be delivered using infusion pumps. In the UK, pumps are recommended for patients with the greatest need and adult use is less than in comparable countries. Previous trials have been small, of short duration and have failed to control for training in insulin adjustment.ObjectiveTo assess the clinical effectiveness and cost-effectiveness of pump therapy compared with MDI for adults with T1DM, with both groups receiving equivalent structured training in flexible insulin therapy.DesignPragmatic, multicentre, open-label, parallel-group cluster randomised controlled trial, including economic and psychosocial evaluations. After participants were assigned a group training course, courses were randomly allocated in pairs to either pump or MDI.SettingEight secondary care diabetes centres in the UK.ParticipantsAdults with T1DM for > 12 months, willing to undertake intensive insulin therapy, with no preference for pump or MDI, or a clinical indication for pumps.InterventionsPump or MDI structured training in flexible insulin therapy, followed up for 2 years. MDI participants used insulin analogues. Pump participants used a Medtronic Paradigm^®Veo^TM(Medtronic, Watford, UK) with insulin aspart (NovoRapid, Novo Nordisk, Gatwick, UK).Main outcome measuresPrimary outcome – change in glycated haemoglobin (HbA_1c) at 2 years in participants whose baseline HbA_1cwas ≥ 7.5% (58 mmol/mol). Key secondary outcome – proportion of participants with HbA_1c≤ 7.5% at 2 years. Other outcomes at 6, 12 and 24 months – moderate and severe hypoglycaemia; insulin dose; body weight; proteinuria; diabetic ketoacidosis; quality of life (QoL); fear of hypoglycaemia; treatment satisfaction; emotional well-being; qualitative interviews with participants and staff (2 weeks), and participants (6 months); and ICERs in trial and modelled estimates of cost-effectiveness.ResultsWe randomised 46 courses comprising 317 participants: 267 attended a Dose Adjustment For Normal Eating course (132 pump; 135 MDI); 260 were included in the intention-to-treat analysis, of which 235 (119 pump; 116 MDI) had baseline HbA_1cof ≥ 7.5%. HbA_1cand severe hypoglycaemia improved in both groups. The drop in HbA_1c% at 2 years was 0.85 on pump and 0.42 on MDI. The mean difference (MD) in HbA_1cchange at 2 years, at which the baseline HbA_1cwas ≥ 7.5%, was –0.24% [95% confidence interval (CI) –0.53% to 0.05%] in favour of the pump (p = 0.098). The per-protocol analysis showed a MD in change of –0.36% (95% CI –0.64% to –0.07%) favouring pumps (p = 0.015). Pumps were not cost-effective in the base case and all of the sensitivity analyses. The pump group had greater improvement in diabetes-specific QoL diet restrictions, daily hassle plus treatment satisfaction, statistically significant at 12 and 24 months and supported by qualitative interviews.LimitationBlinding of pump therapy was not possible, although an objective primary outcome was used.ConclusionAdding pump therapy to structured training in flexible insulin therapy did not significantly enhance glycaemic control or psychosocial outcomes in adults with T1DM.Research priorityTo understand why few patients achieve a HbA_1cof < 7.5%, particularly as glycaemic control is worse in the UK than in other European countries.Trial registrationCurrent Controlled Trials ISRCTN61215213.FundingThis project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full inHealth Technology Assessment; Vol. 21, No. 20. See the NIHR Journals Library website for further project information.