People with body mass index (BMI) ≥35 kg/m² have an approximately 19-fold increased risk of undergoing total knee replacement (TKR); however, many UK integrated care boards (37%) have restrictive policies which limit access to TKR for people based on BMI. Therefore, access to both surgical and non-surgical treatments varies widely, exacerbating existing health inequalities. It remains unclear how decisions about offering TKR are made in people with severe knee osteoarthritis, which weight-loss interventions are provided in practice and how different management pathways relate to patient outcomes among individuals with high BMI.

This study will recruit 400 participants with severe Kellgren-Lawrence grade four knee osteoarthritis from eight secondary care centres in England. All participants, irrespective of BMI, will provide baseline clinical data and patient-reported outcome measures (PROMs), enabling characterisation of baseline associations between BMI, knee function and body image.

A prespecified subgroup of participants with BMI ≥35 kg/m² (minimum n=105) will undergo longitudinal follow-up at 6 months, 12 months and 24 months, including repeat BMI measurement, PROMs and detailed data on access to surgical and non-surgical interventions, including weight-loss strategies and TKR. For those with BMI ≥35 kg/m², statistical modelling will be used to explore associations between baseline factors and longitudinal outcomes including Oxford Knee Score and weight change at 12 months (n≥105). Structural equation modelling will be used to quantify associations between BMI and knee pain/function mediated by psychosocial factors using data from all participants (n=400). A nested qualitative study of surgeons and patients will explore obstacles and preferences in the management of severe knee osteoarthritis.

The study received ethical approval from the West of Scotland REC 5 (Ref: 24/WS/0146) on 10 October 2024. Results will be disseminated through peer-reviewed publications.

ISRCTN42984928.

To develop and validate a polycystic ovary syndrome (PCOS) case definition using administrative health data sources.

A validation study.

Secondary care centre outpatient gynaecology clinic in Calgary, Alberta, Canada.

3951 electronic health records of women aged 18–45 years who presented to a gynaecology clinic in Calgary, Canada, between January 2014 and December 2019 were reviewed. We identified 180 patients with PCOS using the Rotterdam criteria. Participants were excluded if they were biologically male, pregnant at the time of the consultation, did not meet the date criteria or if their consultation note was missing. The chart data were connected to the Practitioner Claims and the Discharge Abstract Database by personal health number.

Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 68 case definitions for PCOS were estimated. Case definition performance was graded.

Of the 68 case definitions tested, none had high validity. The best performing case definitions were: (1) ≥3 instances of International Classification of Diseases-9 code 256.4 (polycystic ovaries) with exclusion codes (sensitivity 23.89%, specificity 99.59%, PPV 74.14%, NPV 96.35%) and (2) 626.X (irregular menstruation), 704.1 (hirsutism) and ≥3 instances of code 256.4 with exclusion codes (sensitivity 2.78%, specificity 99.97%, PPV 83.33%, NPV 95.40%).

We identified several case definitions for PCOS of moderate validity with high PPV (>70%) for case ascertainment in PCOS research in jurisdictions with similar administrative health data. These case definitions are limited by low sensitivity, which should be considered when interpreting research findings.