Double-blind randomised controlled trials (RCTs) and clinical controlled trials in patients receiving methotrexate for rheumatoid arthritis or psoriasis (with or without arthritis), that compared folic or folinic acid supplementation with placebo, were eligible for inclusion. In patients treated with either oral or parenteral methotrexate receiving a dose of at least 7.5mg per week, the intervention had to comprise folic or folinic acid for at least 12 weeks duration during the double-blind phase.
Inclusion criteria for outcomes were not explicitly stated; the analysis was based on various subgroups of side-effect profiles: gastrointestinal; mucocutaneous; haematological; and hepatic.
In the included trials doses of folic acid ranged from 1mg to 5mg per day (five to seven days per week) and folinic acid from 1mg to 5mg per week; duration of follow-up ranged from eight weeks to 30 months.
Two reviewers independently selected studies for inclusion in the review.