Overactive bladder (OAB) syndrome is common with a potentially significant impact on quality of life (QoL). Randomised controlled trials (RCTs) conducted on the management of OAB assess a variety of outcomes and use a wide selection of outcome measures. This makes comparison between trials difficult and evidence presented by subsequent systematic reviews is less robust. A Cochrane review on randomised controlled trials (RCTs) recommended “better reporting of the definition of cure and a standardised approach to subjective assessment. At present no comparison of socio‐economic factors or QoL have been made between anticholinergics and other medications”. Current evidence is therefore inadequate and methodological limitations in RCTs affect their comparability. As a result, the development of a core outcome set is necessary to standardise the future development of RCTs and lead to the production of higher quality evidence. 

This study aims to compare the selection and reporting of outcomes and outcome measures across RCTs on pharmacological therapy for women with idiopathic OAB.

RCTs were searched using EMBASE, Medline and Cochrane database. Full text articles from inception to 2020, written in English, including only adult women were selected. Reported outcomes and outcome measures were extracted, as were interventions, sample size, journal type, commercial funding.  Methodological and outcome reporting quality were evaluated using JADAD and MOMENT scores.

Thirty-eight trials with including 18,316 women met the inclusion criteria. Sixty-nine outcomes were reported, using 62 different outcome measures. The most commonly reported outcome domains were efficacy (86.8%), safety (73.7%)and QoL (60.5%). The most commonly reported outcome in each domain was urgency incontinence episodes (UIE) (52.6%), anti-muscarinic related side effects (76.3%) and change in validated questionnaire scores (36.8%) respectively. 
There was no statistically significant association between journal type (P=0.224) or commercial funding (P=0.111) with quality of outcome reporting. A statistically significant correlation was found between JADAD and MOMENT (Spearman’s rho = 0.548, p<0.05), but no correlation between MOMENT and impact factor or year of publication.

Tolterodine and solifenacin were the most commonly used options in many of the trials. Placebo was used as a control in 19 studies (50.0%). Seven studies evaluated more than two interventions (18.4%). A wide range of outcomes were tested, mainly efficacy (86.5%) assessed through bladder diaries followed by QoL. However, work productivity, patient satisfaction, cognitive function and retreatment probability were reported only once (2.7%). This could be due to the presence of standardised forms that are completed by patients and easily analysed, thus representing reliable tools from which data can be collected. This differs from outcomes such as ‘comfortability with continuing medication’ which would be rather difficult to quantify and subsequently more difficult to analyse. 
Sexual function was underrepresented having only been assessed in one study (2.7%). This was surprising as OAB is known to affect sexual health of women due to the need to wear incontinence pads or having urinary symptoms during intercourse, thereby resulting in low libido and diminished sexual activity (1). There appears to be a lack of RCTs carried out on the effect of pharmacological therapy on female sexual dysfunction. 
Although correlation between JADAD/MOMENT scores and journal types were not statistically significant, trials published in sub-specialist journals generally received higher scores. Caution is needed when interpreting data regarding the specialist journals, as only three were included within the review, thus each study represents 33.3%. Additionally, a statistically significant correlation between MOMENT and JADAD scores indicates that overall methodological quality of the study is usually associated with outcome reporting quality. 

A number of trials did not clearly identify both primary and secondary outcomes; this can increase the risk of reporting bias.

The results from this study, showing variations in outcomes and outcome reporting are in agreement with reporting variations identified in previously published SRs in urogynaecology conditions such as stress urinary incontinence and pelvic organ prolapse (POP) among others conducted and published by CHORUS (2,3). 
Variation in outcome reporting makes comparison and combination of data into meta-analyses difficult and reduces the extent to which patient care can be enhanced as a result of guideline implementation. It is important to remember that outcomes addressed in trials may have different importance to clinicians, patients and policy makers. It is recommended that RCTs encompass all such outcomes in order to produce more meaningful research evidence. 

Outcome variation can be explained as a result of intervention variation in the therapy of OAB. Pharmacological agents may be selected according to local hospital guidelines, clinician and patient preferences (including route of administration such as transdermal vs oral), pharmaceutical company influence and patient co-morbidities or contraindications to certain medications. As a result, certain outcomes may be favoured by certain researchers, leading to a variety of outcomes assessed. Choices of outcomes to collect and report may be influenced by biases of individual researchers or different clinical specialty. For instance, gynaecologists may prioritize assessment of lower genital tract changes, whilst urologists may instead prioritise urinary tract related parameters such as micturition diary variables or urodynamic results.

We identified a wide variation of selected and reported outcomes and outcome measures. The development of core outcome sets (COS) and core outcome measure sets (COMS) may address such variations and lead to higher quality evidence and better patient care. 
We propose the use of most frequently reported outcomes and outcome measures as interim COS and COMS. The main domains we recommend are efficacy, safety and QoL with outcomes: urinary incontinence episodes, urgency episodes and nocturia episodes for efficacy; anti-muscarinic adverse events, other adverse events and discontinuation rates for safety; and changes in questionnaire scores for QoL.

Kim Y, Seo J, Yoon H. The effect of overactive bladder syndrome on the sexual quality of life in Korean young and middle aged women. International Journal of Impotence Research. 2004;17(2):158-163.
Durnea C, Pergialiotis V, Duffy J, Bergstrom L, Elfituri A, Doumouchtsis S. A systematic review of outcome and outcome-measure reporting in randomised trials evaluating surgical interventions for anterior-compartment vaginal prolapse: a call to action to develop a core outcome set. International Urogynecology Journal. 2018;29(12):1727-1745.
Doumouchtsis S, Pookarnjanamorakot P, Durnea C, Zini M, Elfituri A, Haddad J, Falconi G, Betschart C, Pergialiotis V. A systematic review on outcome reporting in randomised controlled trials on surgical interventions for female stress urinary incontinence: a call to develop a core outcome set. BJOG: An International Journal of Obstetrics & Gynaecology. 2019;126(12):1417-1422.