A multicenter uroflowmetry study of healthy women in China

Uroflowmetry is an uroflow measurement technique used to record the voided volume (VV) and flow rate, which can help clinicians objectively evaluate lower urinary tract function. Currently, few uroflowmetry studies have focused on the female population,[1] especially on the uroflow curve standard analysis. Hence, we sought to establish dependable uroflow reference values and nomograms for Chinese women and to evaluate the relationship between uroflow patterns and demographic data. This multicenter survey was conducted between July 2020 and April 2023. Female participants aged 18 years or above were recruited from 11 cities [Supplementary Table 1, https://links.lww.com/CM9/B973] through different modes, such as Internet advertising, social networks, and clinics. Volunteers who were diagnosed with cognitive impairment, urinary incontinence, and individuals with overactive bladder symptom score (OABSS) ≥3, history of lower urinary tract surgery were excluded from the study. This study was conducted in accordance with the principles of the Declaration of Helsinki and all individuals provided informed consent to participate in this study. Ethical approval was obtained from the Beijing Hospital Ethics Committee (No. 2020BJYYEC-085-02). The electronic questionnaire consisted of three parts: a demographic information sheet (Part 1), the Chinese version of the International Consultation on Incontinence Questionnaire-Short Form (ICIQ-SF, Part 2), and the OABSS (Part 3). A home-based uroflowmetry (HBU) system was distributed after the completion of an electronic questionnaire [Supplementary Figure 1, https://links.lww.com/CM9/B973]. Each uroflow curve met the following quality criteria: VV ≥125 mL. Each participant was required to perform ≥3 qualified uroflowmetry tests. To standardize the classification of uroflow patterns, five categories were defined: (1) Fluctuating type (with at least two fluctuations in the curve and amplitude in each wave >1/5 of the maximum value); (2) Prolonged type (time to peak >15 s); (3) Intermittent type (with an interruption number ≥1, and the adjacent uroflow peaks of interruption >3 mL/s); (4) Plateau type (A point = the first point that reaches 70% of the maximum value, B point = the last point that reaches 70% of the maximum value, and slope of the fitted line between A point and B point >–0.7); 5. Bell-shaped (one peak, change before and after the peak less than 1/3 of the flow time, and no other curve-type features). The HBU (Xiaoyu, Cliapath-RJ01, Guangzhou, China) was sent to the National Center of Metrology (Guangzhou; Certificate No. LZT202102176) for testing. With a measured error of 0.1 g, the HBU can provide accurate measurements at 0–1000 mL volumes and maximum flow rates of 0–100 mL/s. The definitions are shown in the Supplementary File 1, https://links.lww.com/CM9/B973. Continuous variables were expressed as mean (interquartile range [IQR]). The Kruskal–Wallis H test was used for comparison among groups. Bivariate correlations were tested using the Spearman's rho and linear regression analysis was used for multivariate analysis. Statistical significance was set at P ≤0.05. Data were analyzed using SPSS statistical software (version 22.0; SPSS Inc., Chicago, IL, USA) and R software (version 3.6.3; The R Project for Statistical Computing, Vienna, Austria). Of the 2461 volunteers enrolled in this study, 406 were excluded (282 volunteers were aged <18 years/lower urinary tract symptoms [LUTS]-related oral medications/LUTS-related surgery history, 124 did not meet the uroflow qualified criteria). A total of 8439 uroflows were collected from 2055 volunteers, and 1994 uroflow data were excluded. The demographic table and uroflowmetry parameters of the age groups are shown in the Supplementary Tables 2-5, https://links.lww.com/CM9/B973. The ages of the volunteers ranged from 18 years old to 93 years old, with an average age of 51.4 ± 17.4 years. Uroflow parameters of the general group were as follows: VV 275.1 ± 104.3 mL, flow time 21.1 ± 9.3 s, Qave 14.0 ± 5.8 mL/s, Qmax 24.8 ± 9.4 mL/s, and time to peak 5.4 ± 3.2 s; uroflow parameter of the aged group were as follows: VV 276.4 ± 104.8 mL, flow time 23.0 ± 10.1 s, Qave 13.1 ± 5.7 mL/s, Qmax 23.5 ± 9.3 mL/s, and time to peak 5.3 ± 2.9 s. Aged women were divided into three groups (60–69 years, 70–79 years, and over 80 years). A comparison of different age groups revealed a significant decrease in flow rate among individuals aged 60 years and above ([Qmax & Qave] P <0.001). After eliminating the voiding volume influence, the correlation between age and corrected Qmax remained steady (cc = –0.18, P <0.001). In the aged groups, the downward trend of the flow rate was more apparent in the 80+ year group (Supplementary Figure 2, https://links.lww.com/CM9/B973, P <0.001). BSA, BMI, Eutocia, and macrosomia showed weak correlations with Qmax (P <0.001). The variable most impacting the flow rate was VV in both univariate and multivariate analyses, which can be described by a quadratic equation [Figure 1]. The equations in general and aged groups are shown in Supplementary File 2, https://links.lww.com/CM9/B973.Figure 1: Flow–volume nomograms: (A) Q max with VV in the general group, (B) Q ave with VV in the general group, (C) Q max with VV in the young age group, (D) Q ave with VV in the young age group, (E) Q max with VV in the aged group, (F) Q ave with VV in the aged group. Percentage values represent confidence limits. M = mean line. 68% and 95% confidence intervals were adopted to construct the flow–volume nomograms. VV: Voided volume.In the analysis of 8433 urinary flow rate records (6 records were deleted because they could not be classified into the five categories), the distribution of uroflow patterns was as follows: 4106 bell types, 2571 fluctuating types, 722 plateau types, 535 prolonged types, and 499 intermittent types. Among participants with bell-shaped urinary flow, 86.3%(3543/4106) rated their Quality of Life (QoL) as either satisfied or very satisfied. However, this percentage decreased to 78.3% (419/535) in the prolonged type. Similar trends were observed in the urination scores, with 73.1% (3001/4106) of those with a bell-shaped flow expressing satisfaction (urination score = 5), whereas the other categories remained below 70% (the satisfaction rates were 1743/2571 for fluctuating type, 311/499 for intermittent type, 464/722 for plateau type, and 314/535 for prolong type). With advancing age, the proportion of bell-type individuals decreased from 53.7% (737/1372) in the 18–29 years age group to 36.1% (65/180) in the >80 years age group (P <0.001). Correspondingly, only 1.9% (78/4106) of bell-type subjects were at risk of sarcopenia, while the prolonged type had 6.9% (37/535) of subjects with sarcopenia risk (P <0.001). Additionally, the prevalence of the bell type was influenced by parity (P = 0.004); 52.4% (840/1602) of nulliparous subjects exhibited a bell-shaped uroflow pattern, whereas in those with three or more childbirths, only 46.9% (450/960) displayed bell-shaped uroflows. Slight differences in BMI and BSA were observed between the different uroflow patterns (P = 0.012 and P = 0.002, respectively). Overall, individuals with predominantly bell-type patterns appeared to have a higher QoL. No significant correlations were identified between smoking, alcohol consumption, educational history, age at first childbirth, and uroflow patterns (P >0.05). With limited research on the elderly female population and uroflow patterns, this multicenter study aimed to provide normal uroflowmetry parameters and analyze the factors influencing uroflow patterns. In this study, we set VV >125 mL and more than three flows within 48 h as the qualifying standard for better simulation of daily urination patterns. The HBU test provides a private and familiar environment that eliminates psychological and environmental influences on subjects.[2,3] Multivariate analysis revealed that age, VV, BMI, and eutocia were associated with the uroflow rate [Supplementary Table 3, https://links.lww.com/CM9/B973]. The correlation between age and uroflow rate remains controversial in current studies, but most studies have reached a consensus that uroflow decreases with age. The positive correlation between BMI and Qmax may be because obese patients often have significantly higher baseline intra-abdominal pressure; similar results were found in another study.[1] Several female uroflow nomograms have been established.[1,4] Haylen et al[4] enrolled 249 female volunteers aged 16–63 years to construct Liverpool nomograms, with the advantage of accommodating a wide range of VVs but limited recruitment in the aged population. In this study, we established a nomogram for the elderly population to fill this gap. Currently, there is no consensus on the standard methodology for uroflow patterns. Although a few studies have established a relatively standard analytical approach, the majority depend on subjective classifications by researchers, thereby raising concerns about credibility. Notably, few researches have analyzed uroflow patterns in the normal population. In this study, we identified a correlation between uroflow patterns and demographic data. These findings laid the groundwork for subsequent in-depth investigations. This study had several limitations. First, patients with LUTS were not included in our study to validate the nomogram, and we plan to enroll more patients with LUTS to validate our nomogram next year. Second, to include a diverse range of ages and regions, the PVR of each volunteer was not recorded; instead, all patients with LUTS were excluded. The strengths of this study include the large sample size of aged volunteers, repetitive measurements, and standard uroflow pattern analysis. This largest female uroflowmetry study provides valuable insights into female uroflow in China. In conclusion, this multicenter study established a flow–volume nomogram and provided uroflow parameters for different age groups; we further evaluated the relationship between uroflow patterns and demographic data. Based on these findings, Qave <10 mL/s in the aged group should not be directly labeled as abnormal, warranting caution in the diagnosis. Bell-type uroflow may reflect a better QoL. Funding This work was supported by a grant of National Key Program (No. 2018YFC2002202). Conflicts of interest None. Registration number Chinese Clinical Trial Registry, No. ChiCTR2100054334.