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Research Studies

Associations between subjective overactive bladder symptoms and objective parameters on bladder diary and filling cystometry

Daan NMP, Schweitzer KJ, van der Vaart GH. Int Urogynecol J 2012; 23: 1619-1624.

Why they did the study

The overactive bladder syndrome [OAB] is defined by the International continence Society [ICS] as: urinary urgency, usually accompanied by frequency and nocturia with or without urgency urinary incontinence, in the absence of urinary tract infection or other obvious pathology. However, the importance of the urgency symptom in the diagnosis of OAB as well as the evaluation of treatment effect has been questioned in the scientific literature. The objective of this study was to assess the association between subjective OAB symptoms and objective parameters such as bladder diary and filling cystometric measurements.

How they did it

This was a retrospective cohort study using the hospital database of women who were referred to the urogynecology service between 2003 and 2009. The study population was 3,280 women with completed 48-h bladder diaries and 2,153 women with available information on filling cystomety. As part of the routine work-up, all women filled out the Urinary Distress Inventory (UDI).

Four lower urinary tract symptoms (LUTS) from the UDI that are in concordance with ICS definitions of OAB were selected. Frequency “Do you experience frequent urination?”, urgency “Do you experience a strong feeling of urgency to empty your bladder?”, nocturia “Do you experience frequent urination at night?”, urgency incontinence “Do you experience urine leakage related to a feeling of urgency?” . Information extracted from the bladder diaries was: daytime urinary frequency, nocturnal frequency, minimum voided volume, maximum voided volume, mean voided volume and incontinence episodes. Filling cystometry was performed at an infusion rate of 50 mL/min conforming to official ICS guidelines.

Symptoms that proved to be significantly associated with bladder diary and filling cystometry parameters were entered into a linear multiple regression analysis with the bladder diary and cystometry items as dependent variables.

What they found

The mean age of the studied population was 54.8 years (±14.7 years) and 85.2% were parous women. The vast majority of women (92%) experienced more than one bothersome LUTS. The combination of bothersome urgency, frequency, and nocturia was reported by 34.4% of women and 26.2% of women additionally experienced urgency incontinence.

The presence of bothersome OAB symptoms showed a statistically significant association with almost all bladder diary and filling cystometry parameters. The frequency symptom was best associated with daytime frequency, the nocturia symptom with nocturnal frequency, and the urgency incontinence symptom with incontinence episodes. Bladder diary and filling cystometry recorded filling volumes were significantly smaller in women with bothersome OAB symptoms than in women without bothersome OAB symptoms. Although statistically significant associations were found for the urgency symptom, the effect sizes were small.

After multivariate analysis for other OAB symptoms, the factor that was most strongly associated with bladder diary daytime frequency was the frequency symptom. Frequency and nocturia are most strongly associated with voided volumes recorded using the bladder diary and filling cystometry. Urgency and urgency incontinence symptoms, however, were no longer significantly associated with most bladder diary and filling cystometry parameters.

Why it matters

The OAB syndrome represents a group of prevalent urinary symptoms that are known to have a negative impact on quality of life. Population-based studies in women report a prevalence of OAB that varies between 9 and 36 % with a substantial rise in prevalence with increasing age. Approximately 50% of women with OAB reported experiencing symptoms that were bothersome in their daily life. With the current global trends in population ageing, OAB is becoming a significant public health problem in the geriatric female population.

The presence of subjective urgency is now considered mandatory and the key symptom for making the diagnosis of OAB as well as measuring the treatment outcome. Several studies, however, have shown that that the severity of urgency symptom is poorly correlated to micturition parameters and therapeutic response. In contrast, the occurrence of the OAB syndrome is associated with objectively defined abnormalities of bladder function that could be demonstrated by a bladder diary or filling cystometrogram with a significant and measurable difference following treatment. The results of this large cohort study showed that of all four cardinal OAB symptoms, the frequency symptom showed the strongest association with daytime urinary frequency, nocturia with nocturnal frequency and urgency incontinence with incontinence episodes as measured in the bladder diary. The frequency and nocturia symptoms showed almost equal and strong associations with bladder volumes as measured in the bladder diary and by filling cystometry. The key symptom of the OAB syndrome, urgency, was either not at all or only poorly associated with objective parameters from the bladder diary and filling cystometry. The findings further support using frequency and incontinence episodes as the primary treatment outcome parameters in OAB studies, as opposed to urgency, as these symptoms show the best associations between subjective and objective parameters.

This study was, however, retrospective, hospital-based and the patient cohort did not include men. Further prospective studies in community- dwelling women and men are needed to verify these findings.

Next question

There has been ongoing debate in the urological community about the accuracy and content of the definition of OAB syndrome ever since its first introduction into the official standardized terminology by the ICS. The emphasis on urgency as the key symptom was based on limited scientific evidence. Furthermore, the urgency symptom is notoriously difficult to define subjectively for both the patient and provider. The individual perception of urgency makes it almost impossible to create a uniform definition for the heterogeneous patient population with OAB symptoms. In fact, frequency and incontinence episodes, and not urgency, are used as the primary outcome measures in many trials that evaluate the treatment of OAB.

Further research should identify which symptom(s) contained in the official definition of the OAB syndrome are mainly responsible for the functional bladder abnormalities observed and could be used as the most sensitive primary outcome to measure the effect of treatment. This will provide evidence whether or not urgency should still be included in the constellation of symptoms required to make the diagnosis of the OAB syndrome. Until these data are available, it is important to be aware in clinical practice that there are subjective and objective diagnostic criteria for the OAB syndrome and that using more than one criterion increases the sensitivity of diagnosis and the assessment of therapeutic response.

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