First morning voided volume useful for OAB evaluation

By Joanna Lyford, Senior medwireNews Reporter

Measuring the first morning voided volume (FMV) may be helpful for evaluating symptom severity in patients with overactive bladder (OAB), researchers believe.

Writing in Urological Science, the Taiwanese team says that FMV helps to identify small-volume bladders and is particularly useful in patients who find it difficult to complete frequency–volume charts (FVC).

Researchers led by Alex Tong-Long Lin (Taipei Veterans General Hospital) recruited 102 patients who were being investigated for OAB symptoms. The patients were asked to complete a 3-day FVC and FMV, were assessed with the Overactive Bladder Symptoms Score (OPABSS) questionnaire and underwent urodynamic studies.

The patients’ mean age was 66.8 years and 59 were female. The mean cystometric capacity was 173.8 mL and the mean FMV was 196.6 mL; the difference between these values was statistically significant and the two parameters significantly correlated.

The mean total score on the OABSS was 10.3. OABSS scores did not correlate with FMV but negatively correlated with cystometric capacity; this was true both for the total score and the nighttime frequency subscore.

Interestingly, mean FMV positively correlated with mean voided volume (r=0.456) and negatively correlated with mean voiding frequency (r=–0.246) and mean nighttime frequency (r=–0.365).

Functional bladder capacity ranged from 84 to 1100 mL (mean 349.6 mL) and 47 patients (46.1%) were classified as having a small functional bladder capacity. Maximal FMV had excellent sensitivity and moderate specificity for predicting these patients, at 100% and 43.3%, respectively. On both measures FMV outperformed cystometric capacity, which had a sensitivity of 95.9% and specificity of just 15.1%.

Combining FMV with cystometric capacity reduced sensitivity to 95.9% but improved specificity to 50.9%.

Lin and co-authors note that while FVCs provide objective data, “the effort required to record each and every voiding episode is labor intensive, and FVCs with longer duration such as 1 week or 2 weeks may inevitably become a burden and decrease compliance rates.”

The researchers conclude: “FMV is a relatively dependable and easily recorded item in the FVC when the credibility of the chart is put into question.” They add: “The usage of FMV might be extended in the clinical scenario, and further investigations should be considered to better determine its effectiveness.”

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