The relationship between objective frequency-volume chart data and the I-PSS in men with lower urinary tract symptoms

The International Prostate Symptom Score (I-PSS) is considered a benchmark in defining the severity of lower urinary tract symptoms (LUTS). However, its relationship with variables of the frequency-volume (FV) chart, an objective measure of LUTS, is not well understood. We analyzed this relationship between the I-PSS and FV chart variables in men with LUTS.

Patients referred for the investigation of uncomplicated LUTS completed an I-PSS and a 3-d FV chart. Correlation coefficients were used to describe the relationship between total I-PSS and its components with the FV variables. The distributions of FV variable scores within the categories of I-PSS severity were also examined. The effect of patient's quality of life score on I-PSS and FV variables was analyzed using regression.

A total of 104 patients completed both the I-PSS and FV chart. The association between FV variables and I-PSS scores was generally weak, with 24-h frequency being the strongest (r = 0.43) and with considerable overlap within each severity category. There was weak association between the I-PSS for nocturia and urgency and their FV counterparts. The number of self-reported nocturnal voids tended to be overestimated. These discrepancies were partly explained by the patient's quality of life rating, which reduced the level of variation between I-PSS score and FV variables and accounted for some of the overestimation.

Weak associations were found between the self-rated I-PSS scores and FV measures of voiding, suggesting that the accurate assessment of LUTS requires self-reported measures of symptoms and objective measures of voiding behaviour. Significant differences between the two types of data might be explained by perceived quality of life.