Rationale: The overactive bladder syndrome is diagnosed clinically by using the ICS criteria of ≥8 micturitions and at least 1 urgency episode per 24 hours. To determine whether patients fit the criteria, micturition diaries ('sensation-related bladder diaries') and other symptom questionnaires with considerable limitations are used. This makes it difficult to get a good impression of the fluctuation of complaints during the day / week. These limitations are overcome using the Experience Sampling Method (ESM). This is an electronic questioning method which is characterized by repeated and random, momentary assessments in the subject's current environment and state. This study follows other successful ESM studies done within the Gastroenterology and Psychiatry Department. The aim of this study is to evaluate if the ESM is more accurate in the assessment of urological complaints in OAB compared to the current assessment with the use of the sensations-related bladder diaries (SR-BDs) and retrospective questionnaires. Furthermore the aim is to assess the reliability and validity of this OAB-specific electronic patient-reported outcome measure (ePRO), based on the Experience Sampling Method-principle, for symptom assessment and assessment of triggers for symptoms in OAB.

Objective: To evaluate the accuracy of the ESM to assess urological complaints in OAB compared to SR-BDs and retrospective questionnaires. To assess content validity, reliability and the accuracy to validate the developed ePRO in OAB patients.

Study design: The ESM study is a multicentre, prospective, cross-sectional study.

Study population: 66 OAB patients will be recruited at the outpatient Pelvic Care Centre in Maastricht UMC+, Zuyderland Hospital and University Hospital Antwerp, 66 healthy volunteers will be recruited as well.

Methods: In a period of 7 days, participants will fill out an electronic ESM assessment at 10 random moments during the day. Moreover, they will fill out a sensation-related bladder diary (SR-BD) during the last three consecutive days of filling out the ESM and several symptom questionnaires at the end of the study period.

Main study endpoints: The main study outcome comprehends the psychometric properties of the PROM for symptom assessment of OAB symptoms. Secondary outcomes are increase in ESM score for OAB symptoms and environmental and psychosocial factors (e.g. as measured by the PROM) from one time point (t-1) to the next (t).

The overactive bladder syndrome (OAB) is defined by the International Continence Society (ICS) as a symptom complex of urgency, usually with frequency and nocturia (awakening at night to void), with (OAB wet) or without (OAB dry) urinary urgency incontinence. Urgency is the complaint of a sudden compelling desire to pass urine, which is difficult to defer. OAB is clinically diagnosed using the ICS criteria of ≥8 micturitions and at least 1 urgency episode per 24 hours.

It is estimated that approximately 16-17% of the adult population of the Western world is affected by OAB. The incidence of OAB, both wet and dry increases by age, and because of the worldwide ageing of the population, the number of adults affected by urinary urgency incontinence (UUI) would increase. The health care costs of OAB are high, and work productivity can be significantly impacted as well. In addition, OAB can be associated with comorbidity and increased mortality. Furthermore, OAB with and without incontinence has been associated with significantly lower quality of life scores compared to matched controls without voiding complaints. It is of particular interest that OAB does not only affect the patients, but also has an impact on family members.

There is a strong association between OAB and psychiatric comorbidities such as depression, anxiety and stress. This association is most likely bidirectional.

The current methods of diagnosis rely on voiding diaries (the sensation-related bladder diary) and retrospective questionnaires.

Retrospective, self-reported outcomes have important limitations. Firstly, there is a high risk for recall bias, in which retrospective information consists of a reconstruction of a few specific moments rather than a reliable reflection of symptoms over a predefined period of time. Furthermore, it is well described that memory retrieval is influenced by the individual's environment and mental state at the time of recall, known as ecological bias. In conclusion, patient experiences about symptoms in the past can be significantly distorted when retrospectively reported. Furthermore, lack of patient compliance is an important disturbing factor in recalled assessments. Studies that employed paper diaries in a population of patients with chronic somatic pain to measure symptoms resulted in very low patient compliance: only 11% actual compliance, but up to 80% fake compliance was determined, the latter presumably resulting from filling in diaries after the proscribed time window.

The Experience Sampling Method (ESM), also referred to as Ecological Momentary Assessment (EMA), may overcome these limitations. ESM is an electronic questioning method characterized by random, repeated assessments in the subject's current state and environment, for several consecutive days. A digital device sends out an auditory beep at random moments during the day, to which subjects have to respond by completing several assessments at the device. The assessments are identical between the moments. Hereby, ESM offers the opportunity to reduce the risk for recall bias and to capture symptom variability over time with taking into account contextual, social and psychological factors, which might have an impact on symptom reporting.

ESM has already been used in different patient populations with different disorders, such as; irritable bowel syndrome (IBS), depression, Parkinson's Disease and mental illness in a broad sense.

ESM has proven to be a viable and novel approach to assess symptoms, affective states and contextual factors at the level of the individual subject. It provides precise, prospective information that may contribute to clinical practice with several distinct advantages over traditionally used (retrospective) assessment of mental health related phenomena. OAB shows fluctuating symptom patterns in which urological complaints might be influenced by daily life factors as well as psychological and psychiatric comorbidities. To our knowledge, there are no previous studies on the use of ESM in a urological patient population. In order to study the performance of ESM in a population as such there is a need for developing a patient-reported outcome measure suitable for real-time symptom assessment of urological symptoms, using the ESM principle. Patient-reported outcome measures (PROMs) are assessment methods completed by patients, and are meant to capture one or several aspects of a disease course or health status. Focus group research in OAB patients was done for item selection and to evaluate the quality of the PROMs according to the ESM principle. The outcomes of the focus groups have been discussed in an expert meeting and a final questionnaire has been constructed, specifically for the ESM in the urological patient population. Now, this OAB-specific ESM tool should be tested to see if there is a difference between symptom scores on ESM and the currently used retrospective reports and SR-BDs. Furthermore content validity, reliability and the accuracy will be tested to validate the developed ePRO in OAB patients. Additionally, specific triggers for the onset of OAB complaints will be objectified, with use of the OAB specific ESM tool. It will be objectified if there is a direct link between OAB and psychiatric disorders as depression, anxiety and stress too.

Summarizing, electronic, repeated symptom assessments during daily activities should assure ecological validity and eliminate recall bias, lead to higher compliance rates, and capture symptom variability during the day. For these reasons it is expected that the Experience Sampling Method (ESM) may prove to be a more objective tool for evaluation and quantification of urgency and other urological complaints that will overcome the limitations of currently used retrospective symptom assessment methods in OAB.

Inclusion criteria OAB patients Patients between 18-70 years with either subjectively experienced OAB for which they have sought medical help or have been diagnosed with OAB by a medical physician. Participants need to be able to understand written Dutch and speak the Dutch language, since the ESM app will be conducted in Dutch. They also have to understand how to practice the ESM tool.

Inclusion criteria healthy volunteers

• Age between 18 and 70 years;
• Male and female
• Ability to understand and speak Dutch;
• Ability to understand how to utilize the ESM tool.

Exclusion criteria OAB patients

A potential subject who meets any of the following criteria will be excluded from participation in this study:

• Patients with a clear anatomical or other urological cause for OAB (e.g. bladder cancer, benign prostate hyperplasia (BPH), prostate cancer, urolithiasis, chronic or acute urinary tract infections (UTI), neurological disease).
• Patient with severe stress incontinence
• Pregnancy

Exclusion criteria healthy volunteers

• Current or past diagnosis of lower urinary tract symptoms;
• No more than one urinary tract infection in half a year.
• Start-up of regularly used medication from one month before inclusion until the end of study participation.
• Pregnancy

Thirty-three male and thirty-three female OAB patients will be recruited at the outpatient Pelvic Care Centre in Maastricht UMC+ and at the outpatient clinic of Zuyderland Hospital and University Hospital Antwerp. Patients will be diagnosed with OAB by their urologist using the ICS criteria for OAB.

Furthermore, thirty-five male and thirty-five female healthy volunteers will be included in order to exploratively evaluate the ability of ESM to discriminate between OAB patients and healthy controls, in terms of triggers for the occurrence and/or persistence of urological symptoms. This control group will be sex- and age-matched to the group of OAB patients.