Development of a clinical decision support tool for Primary care Management of lower Urinary tract Symptoms in men: the PriMUS study

Background
Lower urinary tract symptoms particularly affect older men and their quality of life. General practitioners currently have no easily available assessment tools to diagnose lower urinary tract symptom causes. Referrals to urology specialists are increasing. General practitioner access to simple, accurate tests and clinical decision tools could facilitate management of lower urinary tract symptoms in primary care.

Objectives
To determine which of several index tests in combination, best predicted three diagnoses (detrusor overactivity, bladder outlet obstruction and/or detrusor underactivity) in men presenting with lower urinary tract symptoms in primary care. To develop and validate three diagnostic prediction models, and a prototype primary care clinical decision support tool.

Design
Prospective diagnostic accuracy study. Two participant cohorts, for development and validation, underwent simple index tests and a reference standard (invasive urodynamics).

Setting
General practices in England and Wales.

Participants
Men (16 years and over) consulting their general practitioner with lower urinary tract symptoms.

Sample size
Separate calculations for model development and validation cohorts, from literature estimates of detrusor overactivity, bladder outlet obstruction and detrusor underactivity prevalences of 57%, 31% and 16%, respectively.

Predictors and index tests
Twelve potential predictors considered for three diagnostic models.

Main outcome measures
The primary outcome was diagnostic model sensitivity and specificity for detecting bladder outlet obstruction, detrusor underactivity and detrusor overactivity, with 75.0% considered minimum clinically useful performance.

Statistical analysis
Three separate logistic regression models generated with index test variables to predict the presence of bladder outlet obstruction, detrusor overactivity, detrusor underactivity conditions in men with lower urinary tract symptoms.

Results
One model each was developed and validated for bladder outlet obstruction and detrusor underactivity, two for detrusor overactivity (detrusor overactivity main, detrusor overactivity sensitivity analysis 2). Age, voiding symptoms subscore, prostate-specific antigen level, median maximum flow rate, median voided volume were predictors for bladder outlet obstruction. Median maximum flow rate and post-void residual volume were predictors for detrusor underactivity. Age, post-void residual volume and median voided volume were included in detrusor overactivity main model, while age and storage symptoms subscore predicted detrusor overactivity sensitivity analysis 2.

For all four models, sensitivity of 75.0% could be achieved with a specificity of 74.2%, 47.3%, 45.6% and 46.2% for bladder outlet obstruction, detrusor underactivity, detrusor overactivity main and detrusor overactivity sensitivity analysis 2 models, respectively. Similarly, a specificity of 75.0% could be achieved with a sensitivity of 71.3%, 39.8%, 33.3% and 62.7% for bladder outlet obstruction, detrusor underactivity, detrusor overactivity main and detrusor overactivity sensitivity analysis 2 models, respectively.

The prototype tool (not yet intended for use in practice) is available at Primary care Management of lower Urinary tract Symptoms decision aid for lower urinary tract symptoms (shinyapps.io).

General practitioner feedback during tool development and small-scale user-testing in simulated consultation scenarios was favourable. Patients supported such management in primary care.

Strengths/limitations
This was a prospective, multicentre study in an appropriate primary care population. Most of the index tests are possible routinely in primary care or at home by patients. The diagnostic models were validated in a separate cohort from the same population.

Limitations include that target condition prevalences may differ in other populations.

Conclusion
We identified sensitivities and specificities of diagnostic models for detrusor overactivity, bladder outlet obstruction and detrusor underactivity in routine United Kingdom practice and developed a prototype clinical decision support tool.

Future work
Economic modelling, a feasibility trial and powered randomised controlled trial are needed to evaluate the Primary care Management of lower Urinary tract Symptoms tool in practice.

Study registration
Current Controlled Trials ISRCTN10327305.