Komolmit 2017a.

Study characteristics
Methods	Randomised double‐blind, placebo‐controlled clinical trial with parallel‐group design (2 groups)
Participants	Country: Thailand Number of participants randomised: 80 (46% women), aged 18 to 70 years, mean age 52 years Inclusion criteria: patients with CHC Exclusion criteria: none stated
Interventions	Intervention: vitamin D2 (ergocalciferol 60,000 to 100,000 IU (depending on vitamin D status)) (n = 40) Control: placebo (n = 40) Orally, weekly for 6 weeks The dose of vitamin D2 was based on the ranges of vitamin D deficiency, as follows: mild deficiency (20 to ≤ 30 ng/mL) 60,000 IU/week; moderate deficiency (10 to ≤ 20 ng/mL) 80,000 IU/week; and severe deficiency (≤ 10 ng/mL) 100,000 IU/week. Each vitamin D2 capsule contained 20,000 units. The total dosage was divided into 2 separate doses given on Monday and Friday.
Outcomes	Primary outcomes: T‐helper 1/2 cytokines, IP‐10 and DPP‐IV levels Secondary outcomes: vitamin D level
Stated aim of study	To assess the changes in serum levels T‐helper cells associated cytokines, IP‐10 and DPP‐IV, without influences driven by interferon treatment, after a short‐term period for correction of vitamin D deficiency in chronic hepatitis C patients
Notes	All participants completed the trial. The trial was conducted between April 2012 and April 2013.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "The randomization sequence was stratified with a 1:1 allocation using random block sizes of 4 based on computer generated method based (www.randomisation.com)."
Allocation concealment (selection bias)	Low risk	Quote: "The randomization was performed by a research assistant without involvement in clinical trial. Details of the allocated group were given in sequentially numbered, opaque, sealed envelopes. After patient enrollment, the research assistant will open the envelope and inform stratified groups (A or B) to the investigators."
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "The vitamin D2 (Ergocalciferol) and placebo were prepared by a pharmacist in a capsule form and identical in appearance. They were prepacked in a bottle for six‐week supplement and consecutively numbered for each CHC patient according to the randomised results."
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Blinding of outcome assessment ensured, and it is unlikely that the blinding could have been broken.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Missing data were unlikely to make treatment effects depart from plausible values. All participants completed the trial.
Selective reporting (reporting bias)	Low risk	The trial was registered in the Thai Clinical Trials Registry, which was based on World Health Organization criteria under registration number TCTR20160429001.
Other bias	Unclear risk	Trial may or may not have been free of other factors that could have put it at risk of bias, such as academic bias.