A detailed analysis of outcome reporting from randomised controlled trials and meta-analyses of inguinal hernia repair

Introduction: Evidence is needed to justify whether investment in an internationally agreed core outcome set for inguinal hernia surgery is needed. This study aimed to assess outcome reporting from randomised controlled trials (RCTs) and meta-analyses in inguinal hernia surgery.

Methods: RCTs and meta-analyses comparing surgical technique or mesh type for primary inguinal hernia repair were systematically identified. Verbatim details, type, frequency and definition of clinician-observed and -assessed outcomes were summarised. Patient-reported outcome measures (PROMs) were analysed for instrument validity and frequency of domain reporting.

Results: 40 RCTs (10,810 patients) and 7 meta-analyses (17,280 patients) were identified. No single PROM was reported by all studies. There were 58 different clinician-observed outcomes, with recurrence (n = 47, 100 %), wound infection (n = 33, 70.2 %), haematoma (n = 31, 77.5 %) and seroma formation (n = 22, 46.8 %) being most frequently reported. All studies measured patients’ views, although only 12 (30.0 %) used validated instruments. The SF36 was the most commonly used multi-dimensional valid PROM (n = 7), and a visual analogue scale assessing pain (n = 32) was the most frequently used unidimensional scale. Non-validated questionnaires assessed 25 other aspects of patients’ health. Two meta-analyses defined recurrence and three chronic pain although neither ensured that included RCTs adhered to the definitions.

Conclusions: Outcome reporting from RCTs concerning inguinal hernia repair is inconsistent and poorly defined, limiting meta-analyses, which themselves do not control for the differing definitions of assessed outcomes. This study justifies investment in a standardised core outcome set for inguinal hernia surgery, to improve outcome reporting and evidence synthesis.