Rejholec 1980.

Methods	Design: RCT Number of centres: NA Treatment duration: 6 months Flare design: No Wash‐out period: No Time point of assessments: BL, 1, 2, 3, 4, 5, 6 months
Participants	Inclusion criteria: Diagnosis of AS verified clinically and radiographically. Exclusion criteria: None reported. Classification: NA Tolfenamic acid (600 mg): Number of participants: 25 Number of completers: 24 Age (mean (SD)): 38.6 (2.7) Male (%): 84 Symptom duration: NA Disease duration (mean (SD)): 13.9 (2.4) years HLA‐B27 positive (%): 100 Indomethacin (75 mg): Number of participants: 25 Number of completers: 21 Age (mean (SD)): 35.6 (2.7) Male (%): 88 Symptom duration: NA Disease duration (mean (SD)): 10.4 (2.1) years HLA‐B27 positive (%): 100
Interventions	Tolfenamic acid (600 mg) vs Indomethacin (75 mg) Co‐medication: Not reported
Outcomes	Extracted outcomes: Withdrawals due to adverse events
Notes	The outcomes pain on Likert scale, ESR, chest expansion and Schober's test were also presented, but these data could not be used due to presentation in graphs from which the data could not be extracted. Funding source: Not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"The patients were sequentially given a study number; each study number had previously been assigned to either the tolfenamic acid or the indomethacin group by a person not directly involved in the trial, using a table of random numbers."
Allocation concealment (selection bias)	Unclear risk	No information provided on allocation concealment.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	"The drugs were administered in gelatin capsules of identical appearance."
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No information provided on blinding of outcome assessors.
Incomplete outcome data (attrition bias) All outcomes	Low risk	"Four patients receiving indomethacin interrupted the 6‐month trial… In the tolfenamic acid group there was 1 discontinuation…" Outcome data is most likely available for > 84% of the study participants.
Selective reporting (reporting bias)	Low risk	All outcomes stated in the methods are reported.
Other bias	Low risk	No other bias was detected.