van Veen 2007.

Methods	Between September 1993 and January 1996, 300 participants scheduled for repair of unilateral primary inguinal hernia were randomised to either non‐mesh (n = 150) or mesh repair (n =150). Six hospitals participated in the study. Participants were followed up at 1 week and 1, 6, 12, 18, 24 and 36 months in an outpatient setting. In the van Veen 2007 study, 153 participants were available for long‐term 10‐year follow‐up.
Participants	Included participants over the age of 18 with primary unilateral inguinal hernia. Participants with bilateral hernias were excluded.
Interventions	Non‐mesh repair (n = 150) According to the surgeon's method of choice, provided that 2‐0 polypropylene sutures were to be used Mesh repair (n = 150) According to strict protocol as described by Lichtenstein and Shulman using polypropylene prosthetic mesh of 7.5 cm x 15 cm
Outcomes	Outcomes measured: postoperative pain; recurrence rate; quality of life; complications; drainage, wound haematoma, wound dehiscence or wound infection; operation related factors including duration of surgery, duration of hospital stay, cost.
Notes	Mesh inguinal hernia repair was associated with a lower recurrence rate than non‐mesh repair. No differences were found in complication rate, postoperative pain and quality of life, and mesh repair proved to be cost‐effective. 10‐year follow‐up study provides evidence that mesh repair of inguinal hernia is equal to non‐mesh repair with respect to long term chronic pain. But based on the present long‐term findings, it is concluded that non‐mesh primary inguinal hernia repair should be completely abandoned in adults if recurrence rates are to be reduced.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomisation was achieved by calling an independent randomisation centre, where computer‐generated lists were available, stratified by hospital.
Allocation concealment (selection bias)	Low risk	Use of centralised randomisation service
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	No blinding of participants or personnel was described.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Outcome assessors performing physical examination to determine recurrence or complications were blinded to the intervention received.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Incomplete data was addressed; reasons for withdrawal and exclusion were reported. It was recognised by the study investigators that 10‐year follow‐up was difficult to obtain.
Selective reporting (reporting bias)	High risk	The definition of postoperative pain is considered as a dichotomous outcome and positive if it meets the criteria of "persistent pain and discomfort interfering with daily activity". In the earlier 2002 version of the study, quality of life was measured as an outcome, and other variations of pain i.e. paroxysmal pain and groin numbness were considered. Neither of these outcomes were discussed or reported in the 2007 publication.
Other bias	Low risk	None identified