de Jong 1999.

Methods	This was a randomised, double‐blind, internally‐controlled study. Intention‐to‐treat analysis was performed.
Participants	Inclusion criteria of the trial The trial included 57 adult participants (2 x 57 hands) with dystrophic fingernail psoriasis. (There were 36 men and 21 women; age range = 21 to 77 years; mean age = 45.8 years). The duration of fingernail psoriasis had a mean of 9.9 years (range = 0 to 46 years). A minimum NAS score of 5 was required for inclusion. Exclusion criteria of the trial The trial tested participants for onychomycosis by means of a KOH test and mycological culture, and they were excluded if positive.
Interventions	Left hand versus right hand treated with either of the following: 1% 5‐fluorouracil in Belanyx lotion; or Vehicle Belanyx lotion The intervention was applied once daily and covered with a plaster for 12 weeks, with a follow‐up period of 4 weeks.
Outcomes	Outcomes of the trial Changes in NAS scores of a comparable target nail of each hand, according to a 5‐point rating scale (0 = none, 4 = very severe). Assessed NAS parameter were as follows: extent of the nail pitting area (0% to 100%), in steps of 25% + number of pits (0 to > 15), the average of which was defined as nail pitting; subungual keratosis (0 to > 3 mm: measured from nail bed to thickest part); onycholysis (0% to 100%); and oil spots (0% to 100%) Changes in severity score, investigators' opinion: 5‐point rating scale (0 = none, 4 = very severe) Changes in severity score, participants' opinion: 5‐point rating scale (0 = none, 4 = very severe)
Notes	‐
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "...randomised trial."
Allocation concealment (selection bias)	Unclear risk	Comment: The paper provided insufficient details.
Blinding (performance bias and detection bias) Clinician/ Investigator	Low risk	Quote: "...double‐blind study."
Blinding (performance bias and detection bias) Participants	Low risk	Quote: "...double‐blind study."
Blinding (performance bias and detection bias) Outcome assessor	Low risk	Quote: "...double‐blind study." Comment: The blinded investigator was probably the assessor.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Comment: There were no missing outcome data.
Selective reporting (reporting bias)	Low risk	Comment: The trial reported all the expected outcomes.
Other bias	Low risk	Comment: This was free of other sources of bias.