Shamshirsaz 2004.

Methods	Study design: cluster RCT; they randomly selected centres one by one to reach a total number of 593 patients (12 centres) Study duration: 2 years Duration of follow‐up: 442 patients (254 cases in the treatment group and 192 in the control group) were followed for 9 months. 281 patients (160 in the treatment group and 121 in the control group) were followed for an additional 9 months
Participants	Setting: multi‐centre Country: Iran ELISA III checked all patients for HCV antibody detection before enrolling in the study, positive cases were confirmed by RT‐PCR Number: 593 enrolled ◦ Treatment group: 297; 267 negatives and 30 positives by HCV ◦ Control group: 296; 275 negatives and 21 positives by HCV Mean age ± SE (years): treatment group (48.1 ± 0.9); control group (50.6 ± 1.0) Sex (% male): treatment group (59.9); control group (54.2) Exclusion criteria: not reported
Interventions	Treatment group Centres with dedicated HD machines Dialysis membranes were low pressure and used only once and HD machines were bleached and rinsed between dialysis sessions according to the manufacturers' instruction. All machines were located in dialysis wards and not in separate rooms in both groups. Control group Centres with no dedicated HD machines
Outcomes	Incidence of HCV infection in both groups, to evaluate the effect of dialysis machine separation on the spread of HCV infection
Notes	To prevent HCV transmission, educational courses were held for the staff to re‐emphasize the CDC hygienic guidelines Patients were dialyzed for 4 or 4.5 hours, 2 or 3 times/week, using standard HD techniques, patient to staff ratio in the groups wasn't statistically different (3.1 and 3.4 respectively) and all staff members were negative for anti‐HCV
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information about the sequence generation process Randomisation was performed by dialysis centre, it was a cluster randomised trial which included four centres (intervention) compared with eight centres (control)
Allocation concealment (selection bias)	High risk	Allocation concealment was not performed
Was recruitment bias adequately prevented?	High risk	Individuals were recruited to the trial after the clusters had been randomised (the knowledge of whether each cluster is an ‘intervention’ or ‘control’ cluster could affect the types of participants recruited).
Were baseline imbalances (in terms of either the clusters or the individuals) adequately addressed?	High risk	There were baseline imbalances between the randomised groups, but finally they were not controlled for at the design or analysis stage of the study
Blinding of participants and personnel (performance bias) All outcomes	High risk	There was no blinding of participants or personnel
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Insufficient information to permit judgement
Incomplete outcome data (attrition bias) All outcomes	High risk	Intention‐to‐treat analysis was not performed. There was an "available case analysis" done with substantial departure of the intervention received from that assigned at randomisation. Only 74.5% of the patients were followed for 9 months and 47.3% were followed for an additional 9 months They lost > 10% of their population One centre was excluded after randomisation, causing a deviation from protocol
Selective reporting (reporting bias)	High risk	The authors only reported one result, measuring the difference in the incidence of HCV in both groups, based on that issued its findings, did not have secondary outcomes. The authors did not consider the exposure time (i.e. years patients at risk) in determining the rate of seroconversion
Was the study analysed by correct statistical methods (i.e. taking the clustering into account)?	High risk	"Comparisons between groups were made by the chi square test method for categorical variables and by the t test for quantitative variables." The cluster‐randomised trial was analysed by incorrect statistical methods, not taking the clustering into account

CDC ‐ Centers for Disease Control and Prevention; HCV ‐ hepatitis C virus; HD ‐ haemodialysis; SE ‐ standard error