Van Dijk‐de Vries 2015.

Study characteristics
Methods	Lessons learnt from a cluster‐randomised trial evaluating the effectiveness of Self‐Management Support (SMS) delivered by practice nurses in routine diabetes care Clustered RCT (41 clusters and 41 providers), conducted in 1) A regional care group in the South of the Netherlands consisting of 77 family practices. 2) The study involved practice nurses (n = 40) providing care to approximately 4000 patients with diabetes. In Netherlands. 2 arms: 1. Control (usual care) (control arm) and 2. Intervention (biopsychosocial Self‐Management Support (SMS) (intervention arm)
Participants	Control arm N: 147 Intervention arm N: 117, NA, NA Diabetes type: 2 Mean age: 64.56 ± 11 % Male: 53.56 Longest follow‐up: 12 months
Interventions	Control arm: (usual care) Intervention arm: (biopsychosocial self‐management support (SMS)) 1) Case management 2) Promotion of self‐management
Outcomes	Glycated haemoglobin
Funding source	This research was supported by the Dutch Diabetes Research Foundation (Diabetes Fonds) with grant No. 2010.13.1366 (Voice of the Patient programme), and by the ‘Annadal Foundation’ in Maastricht, an independent financial support fund in the field of healthcare. Both the training of practice nurses and operation of the system for registration of SMS were facilitated by the ‘HOZL’ group of collaborating family practices in the eastern part of the Southern Limburg region. During the SMS project, CZ Health Insurance included a fee for SMS in the bundled payment arrangement for diabetes care.
Notes	—
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	The randomisation was performed by an independent research assistant who used a random number seed computer program to assign PNs to study arms, assuming an allocation ratio of 1:1.
Allocation concealment (selection bias)	Low risk	Clustered RCT
Provider's baseline characteristics (selection bias)	Unclear risk	77 family practices, involving 40 practice nurses providing care to approximately 4000 patients with diabetes. Practice nurses were cluster‐randomised in 2 arms. No data on nurses' characteristics are reported in each arm at baseline.
Patient's baseline characteristics (selection bias)	Low risk	More patients with a paid job in the intervention arm (51% vs 32%, P < 0.05); all other characteristics balanced.
Patient's baseline outcomes (selection bias)	Low risk	Table 1, P = 0.429 for HbA1c.
Incomplete outcome data (attrition bias)	High risk	41 patients were lost to follow‐up out of 264 at baseline (15.5%). In 10% of the sample, one follow‐up measurement was missing. 3 patients did not complete the baseline measurement and gave informed consent at the 4‐month follow‐up measurement. Another 23 patients completed only the baseline measurement. Reasons for incompleteness not reported, but their numbers are balanced.
Blinding of participants and personnel (performance bias) and of outcome assessors (detection bias)	Low risk	Our outcome of interest is objective (HbA1c).
Selective reporting (reporting bias)	Low risk	Prospectively registered protocol (protocol registered in February 2011, study started in August 2011). All outcomes of interest are reported.
Risk of contamination (other bias)	Low risk	Clustered RCT. As some PNs worked together in a team, 15 units of analysis were left in the intervention arm and 19 units of analysis in the control arm. PNs working together in a practice were clustered for being randomised to the same trial arm to avoid the risk of contamination if the SMS and usual care would be delivered in the same family practice.
Other bias	Unclear risk	Made few changes to clusters after randomisation (control arm: 21 to 19, and intervention: 20 to 15). Quote: "From the 77 family practices that were approached between April and June 2011, 40 agreed to participate. Their PNs (n=41) were by randomisation assigned to the intervention arm (20 PNs) and the control arm (21 PNs). After randomisation, but before patient recruitment, one family practice in the intervention arm withdrew from study participation due to the heavy workload of the PN. This left 19 PNs who received training in SMS and integrated it into their daily practice, and 21 PNs in the control arm who provided usual care. As some PNs worked together in a team, 15 units of analysis were left in the intervention arm and 19 units of analysis in the control arm". Other Quote: "Also, as PNs’ integration of SMS into consultations could have fluctuated during follow‐up, they may have missed study participants. Registration bias may have also occurred. PNs needed to open an extra data file to record the process and outcomes of SMS. This step might have created a barrier to their compliance."