Vosoghinia 2016.

Methods	Randomised clinical trial with parallel group design (2 groups).
Participants	68 participants (13% women), mean age 42 years, with chronic HCV genotype 1,2,3,4. Inclusion criteria: adult patients with chronic HCV infection (> 6 months) and detectable serum levels of HCV RNA (genotype 1, 2, 3 or 4) with compensated liver disease fulfilling the following criteria of an absolute neutrophil count above 1500 permm3, a platelet count above 90,000 permm3, and a normal haemoglobin level. Exclusion criteria: co‐infection with hepatitis B virus or HIV, decompensated liver disease (Child‐Pugh classification B or C), autoimmune or metabolic liver disease, hepatocellular carcinoma, a history of anti‐HCV therapy or use of medications which alter vitamin D3 levels or metabolism (calcium, vitamin D supplementation, oestrogen, alendronate, isoniazid, anticonvulsants, and orlistat), or a history of diarrhoea or malabsorption syndromes like celiac and chronic pancreatitis or those with renal or parathyroid diseases.
Interventions	Intervention: PEG‐IFN‐α‐2a (180 μg) + oral ribavirin (Rebetol, MSD) dosage determined based on patient’s weight and genotype, was administered for 48 weeks in patients with genotypes 1 and 4 and for 24 weeks in those with genotypes 2 and 3, and vitamin D3 1600 IU/day (n = 34). Control: PEG‐IFN‐α‐2a (180 μg) + oral ribavirin (Rebetol, MSD), dosage determined based on patient’s weight and genotype. PEG‐IFN‐α‐2a was administered for 48 weeks in patients with genotypes 1 and 4 and for 24 weeks in those with genotypes 2 and 3 (n = 34). Vitamin D3 was administered for 12 weeks.
Outcomes	Primary outcome: EVR defined as undetectable HCV‐RNA at 12 weeks' post‐treatment.
Stated aim of study	To assess the influence of vitamin D supplementation on viral response to PegINF/RBV therapy
Notes	The research council of Mashhad University of Medical Sciences,Mashhad, Iran financially supported this study.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Method of sequence generation not specified.
Allocation concealment (selection bias)	Low risk	Participant allocations could not have been foreseen in advance of, or during, enrolment. Allocation sequence hidden in sequentially numbered, opaque, and sealed envelopes.
Blinding of participants and personnel (performance bias) All outcomes	High risk	No blinding, and assessment of outcomes likely to be influenced by lack of blinding.
Blinding of outcome assessment (detection bias) All outcomes	High risk	No blinding, and assessment of outcomes likely to be influenced by lack of blinding.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Missing data unlikely to make treatment effects depart from plausible values.
Selective reporting (reporting bias)	Low risk	All predefined outcomes reported fully.
For‐profit bias	Low risk	The trial appeared to be free of industry sponsorship or other type of for‐profit support that could manipulate the trial design, conductance, or trial results.
Other bias	Unclear risk	The trial may or may not have been free of other components that could put it at risk of bias.