Prospective multicentric validation of a novel uroflowmetry device (Pflow™) against conventional gravimetric uroflowmetry

ABSTRACT

Background:

Conventional gravimetric uroflowmetry, although reliable, is restricted to clinical settings and may be influenced by inhibition and logistical constraints. The present study device is a gravity-driven volumetric uroflowmetry device that uses a calibrated multichamber collection system to derive standard uroflowmetry parameters without requiring electronics or external power. This study was done to assess the agreement between a novel portable uroflowmetry device (Pflow™) and conventional gravimetric uroflowmetry.

Materials and Methods:

This prospective two-center, comparative study was conducted over 12 months (July 2023–July 2024) across two tertiary urology centers and included 372 patients (292 males; mean age 50.3 ± 18.5 years). Measurements were recorded simultaneously using both the devices during a single voiding event. Parameters analyzed included voided volume, peak flow rate (Qmax), average flow rate (Qavg), and voiding time. Agreement was assessed using the Wilcoxon signed-rank test, Spearman correlation, intraclass correlation coefficient (ICC), and Bland–Altman analysis.

Results:

No statistically significant differences were observed between the two methods for voided volume (271 mL vs. 270 mL, P = 0.440), voiding time (40 s vs. 38 s, P = 0.204), Qmax (15 mL/s vs. 14.4 mL/s, P = 0.209), and Qavg (9 mL/s vs. 10 mL/s, P = 0.739) and strong correlations were observed (ρ = 0.799–0.963, P < 0.001). ICC demonstrated excellent agreement for voided volume (0.963) and good agreement for all measured flow parameters. Bland–Altman analysis showed minimal bias.

Conclusion:

Pflow™ demonstrates good agreement with conventional uroflowmetry and may serve as a simple adjunct for monitoring urinary flow in clinical settings.

INTRODUCTION

Uroflowmetry is a widely used noninvasive diagnostic tool for evaluating lower urinary tract dysfunction.[1,2,3,4] It provides objective assessment of voiding patterns and plays an important role in the management of lower urinary tract symptoms (LUTS).[1,2] Conventional gravimetric uroflowmetry, although reliable, is limited to clinical settings and may be affected by patient’s inhibitions and logistical constraints.

Home-based uroflowmetry offers a potential solution[5,6,7,8,9,10,11] by enabling assessment in a natural environment and facilitating repeated measurements. Several portable uroflowmetry systems have previously been described, including funnel-based devices, electronic home uroflowmeters, mobile acoustic systems, wearable ultrasound Doppler systems, and tele-home monitoring platforms. However, many of these systems rely on electronic sensors, mobile applications, wireless connectivity, batteries, or external power sources. The present study device is a portable gravity-driven volumetric uroflowmetry device that operates without electricity, electronic sensors, batteries, software, wireless connectivity, or internet access and uses a calibrated horizontally arranged multichamber fluid collection system with controlled outflow to reconstruct the uroflowmetry curve and derive standard uroflowmetry parameters.

This simplified design has the potential to measure all the important parameters of uroflowmetry, reduce the cost and improve accessibility, particularly in resource-limited settings. Therefore, this study evaluated the agreement between the study device and conventional gravimetric uroflowmetry using a simultaneous measurement design to minimize intraindividual variability.

MATERIALS AND METHODS

Ethical considerations

The study was approved by the Muljibhai Patel Society for Research in Nephro-Urology Ethics Committee (MPSRNUEC), MPUH, Nadiad, Gujarat, India (MPUH) (Approval No. EC/977/2023; approval granted on 8 September 2023). The study was conducted in accordance with the institutional ethical standards at both the participating institutes, namely MPUH, India, and Institute of Urology, Dhule. Written informed consent was obtained from all the participants before enrollment.

Study design and population

This prospective two center study was conducted over 12 months (July 2023–July 2024) across two tertiary urology centers. A total of 372 patients (292 males, 80 females; mean age 50.3 ± 18.5 years, included 300 from MPUH and 72 from IOU), were included in the study.

Patients were recruited from both the centers using uniform inclusion and exclusion criteria. A standardized study protocol was followed across both the institutions to ensure consistency in data collection, device usage, and measurement procedures.

Inclusion and exclusion criteria

Adult patients attending the participating urology outpatient clinics and undergoing uroflowmetry as a part of routine clinical evaluation, who were able to undergo a uroflowmetry test, were eligible for inclusion. Patients were required to provide informed consent and achieve a voided volume between 150 mL and 750 mL during the study measurement. The lower threshold of 150 mL was selected in accordance with the accepted uroflowmetry standards to ensure reliable interpretation of the flow parameters, whereas the upper limit of 750 mL corresponded to the maximum capacity of the study device.

Patients who were unable to complete the uroflowmetry, had incomplete recordings, declined participation, or produced voided volumes exceeding 750 mL were excluded from the analysis. Only one voiding episode per participant was included in the study.

Device description and working principle

The study device is a gravity-driven volumetric uroflowmetry device [Figure 1]. It is manufactured from medical-grade plastic (polypropylene) and measures approximately 20 cm × 20 cm × 20 cm. The device is intended as a low-cost disposable or limited-reuse uroflowmetry system. The estimated manufacturing cost is approximately Indian Rupees (INR) 240 per unit, substantially lower than that of conventional electronic uroflowmetry systems.

Figure 1.

Schematic representation of the study device demonstrating the multi-chamber collection system. Urine enters through the inlet and sequentially fills chambers via an overflow pathway. Each chamber has a calibrated outlet aperture (~1 mL/s), enabling gravity-driven controlled flow. The distribution of urine across chambers reflects temporal variation in urinary flow, allowing reconstruction of uroflowmetry parameters

The device consists of two horizontal rows of chambers. Urine is collected through a funnel and enters the upper row, where it passes sequentially through a series of cubical chambers arranged in an overflow pathway. Each chamber is fitted with a calibrated outlet aperture at its base, allowing a near-constant outflow of approximately 1 mL/s into a corresponding lower-row collection chamber. Because each chamber has a known volume, the distribution of urine across the lower collection chambers reflects temporal variations in the urinary flow during the voiding. The controlled outflow through the calibrated apertures enables proportional volume accumulation within the collection chambers over time. This distribution pattern remains consistent across a wide range of inflow rates encountered during a routine uroflowmetry, thereby permitting reconstruction of the flow parameters. Chamber volume data are subsequently processed using a predefined computational algorithm to derive standard uroflowmetry parameters, including voided volume, voiding time, peak flow rate (Qmax), and average flow rate (Qavg). The same algorithm was applied uniformly to all the measurements obtained during the study.

During device development, fluid flow characteristics were initially modelled using computer-aided design-based fluid dynamic simulations to determine appropriate chamber geometry and outlet aperture dimensions. Following manufacture, calibration testing was performed by passing known fluid volumes through individual chambers and measuring the volume discharged through the outlet over time. Aperture dimensions were adjusted iteratively until the desired outflow characteristics were achieved. This calibration process ensured consistent flow behavior across the operating range of the device.

Procedure

The study device was placed directly over the weight transducer of a conventional uroflowmeter, allowing simultaneous measurement during a single voiding event under identical physiological conditions [Figure 2]. The device urine collection pathway was arranged to permit unobstructed urine passage without active flow restriction, splashing, or external overflow before entering the study device and the conventional uroflowmeter simultaneously. The conventional uroflowmeter was zeroed before each measurement. Each participant served as his or her own control, as measurements from both the conventional uroflowmeter and the study device were obtained simultaneously during the same voiding episode. The conventional uroflowmeter generated and printed the reference uroflowmetry report, whereas chamber volume measurements obtained from the study device were photographed. The resulting images were analyzed using dedicated software to quantify the volume in each chamber, and these data were subsequently processed using a predefined computational algorithm to derive the corresponding uroflowmetry parameters for comparison.

Figure 2.

Experimental setup showing simultaneous uroflowmetry using the study device and a conventional gravimetric uroflowmeter. The study device is positioned directly over the weight transducer to ensure identical measurement conditions. The conventional uroflowmetry console generates the reference uroflowmetry recordings, while chamber-volume measurements obtained from the study device are subsequently processed using the predefined computational algorithm to derive uroflowmetry parameters

This paired study design eliminated intraindividual variability and enabled direct comparison between the two measurement methods under identical physiological conditions.

Statistical analysis

Data were analyzed using IBM SPSS Statistics, Version 31.0 (IBM Corp., Armonk, NY, USA). Wilcoxon test, Spearman correlation, intraclass correlation coefficient (ICC), and Bland–Altman analysis were used. P < 0.05 was considered significant. The authors confirm the availability of, and the access to, all the original data reported in this study. The authors have not used artificial intelligence (AI) and AI-assisted technologies, including large language learning models, in the preparation of the manuscript. The authors confirm that they have reviewed the manuscript and take full responsibility for the contents in the article.

RESULTS

A total of 372 patients were analyzed (mean age 50.34 ± 18.52 years). Baseline demographic characteristics of the study population are summarized in Table 1. Most participants were male (78.2%), and the largest age subgroup was between 61 and 70 years.

Table 1.

Baseline demographic characteristics of the study population

Characteristic	Value, n (%)
Total patients, n	372
Age (years), mean±SD	50.34±18.52
Sex
Male	292 (78.2)
Female	80 (21.8)
Age 18–20 years	21 (5.6)
Age 21–30 years	47 (12.6)
Age 31–40 years	57 (15.3)
Age 41–50 years	49 (13.2)
Age 51–60 years	66 (17.7)
Age 61–70 years	75 (20.2)
Age 71–80 years	47 (12.6)
Age >80 years	10 (2.7)

SD=Standard deviation

No significant differences were observed between the two methods [Table 2]:

Table 2.

Comparison of uroflowmetry variables between methods

Variable	Conventional (median, IQR)	Pflow™ (median, IQR)	Z statistic	P	Significance
Voided volume (mL)	271 (190–392)	270 (195–400)	9999.5	0.440	NS
Void time (s)	40 (20–63)	38 (23–63)	4850.0	0.204	NS
Qmax (mL/s)	15 (9–17)	14.4 (9.6–17)	12124.5	0.209	NS
Qavg (mL/s)	9 (6–11.7)	10 (6–11)	6889.0	0.739	NS

*Wilcoxon signed-rank test, *Statistically NS (P>0.05). Q₁=Lower quartile and Q₃=Upper quartile. Qmax=Peak flow rate, Qavg=Average flow rate, IQR=Inter quartile range, NS=Not significant

• Voided Volume: 271 versus 270 mL (P = 0.440)

• Voiding Time: 40 versus 38 s (P = 0.204)

• Qmax: 15 versus 14.4 mL/s (P = 0.209)

• Qavg: 9 versus 10 mL/s (P = 0.739).

Strong correlations were observed (ρ = 0.799–0.963, P < 0.001) between conventional uroflowmetry and the study device.

The Spearman rho correlation highlighted a strong positive relationship between all the variables: Table 3.

Table 3.

Spearman correlation analysis

Variable	ρ (rho)	P	Interpretation
Voided volume	0.963	<0.001	Very strong correlation
Void time	0.870	<0.001	Strong correlation
Qmax	0.799	<0.001	Strong correlation
Qavg	0.813	<0.001	Strong correlation

Qmax=Peak flow rate, Qavg=Average flow rate

ICC 2,1 showed excellent agreement for volume (0.963) and good agreement for flow parameters: Table 4.

Table 4.

Intraclass correlation coefficients

Variable	ICC value	Interpretation
Voided volume	0.963	Excellent agreement
Void time	0.841	Good agreement
Qmax	0.793	Good agreement
Qavg	0.745	Moderate–good agreement

Qmax=Peak flow rate, Qavg=Average flow rate, ICC=Intraclass correlation coefficient

Bland–Altman analysis demonstrated minimal bias and 95% limits of agreement for all the parameters [Figure 3 and Table 5].

Figure 3.

(a) Bland Altman: Voided Volume, (b) Bland Altman: Void Time, (c) Bland Altman: Qmax, (d) Bland Altman: Qavg

Table 5.

Bland–Altman analysis of agreement between conventional and Pflow™ devices

Variable	Mean difference (bias)	SD of differences	95% limits of agreement
Voided volume	−1.9 (mL)	32.7	−65.9 to+62.1 (mL)
Void time	+0.5 (s)	10.4	−19.9 to+21.0 (s)
Qmax	+0.6 (mL/s)	3.2	−5.8 to+6.9 (mL/s)
Qavg	+0.04 (mL/s)	2.8	−5.5 to+5.6 (mL/s)

Qmax=Peak flow rate, Qavg=Average flow rate, SD=Standard deviation

DISCUSSION

This two-center study demonstrates that the study device provided measurements comparable to the conventional uroflowmetry across key parameters. The simultaneous measurement design strengthens validity by eliminating intravoid variability.

The two-center design enhances the generalizability of the findings across different clinical settings and reduces centre-specific bias.

Various portable uroflowmetry systems have been described in the literature.[6,7,8,9,10,11,12,13,14,15,16,17,18,19] Early nonelectronic systems included funnel-based peak flow devices[8,14] described by Smith and Currie, as well as categorized flow measurement systems developed by Pel and Van Mastrigt. Subsequent devices such as Peakometer and CaptiFlow™[9,10] attempted simplified home-based flow estimation. More recent electronic and digital systems include Da Capo™, mobile acoustic uroflowmetry applications, wearable ultrasound Doppler systems, and tele-home uroflowmetry platforms.[11,12,13,14,15,16,17,18,19] Several investigators have reported strong agreement between portable uroflowmetry systems and conventional gravimetric uroflowmetry.[6,15,16,17,18,19] De La Rosette et al. demonstrated improved reliability using portable home uroflowmetry systems,[6] while Lee et al.[15] and Lee et al.[16] showed that mobile acoustic uroflowmetry provided voided volume and flow rate measurements comparable to the standard uroflowmetry. Kato et al. similarly reported no major differences between clinic-based and home based uroflowmetry measurements using the portable “Freeflow” device.[17] The findings of the present study are consistent with these reports and further extend the concept by validating a gravity-driven volumetric system. The principal novelty of the present device lies in its completely passive design. Unlike most contemporary portable uroflowmetry systems that depend on sensors, acoustic recording, ultrasound technology, batteries, mobile applications, or wireless data transmission, the study device uses a calibrated multichamber fluid collection system to generate multiple uroflowmetry parameters without requiring on-site batteries, electronics, internet connectivity, or dedicated hardware. This simplified architecture may offer advantages in terms of affordability, portability, disposability, ease of use, and applicability in low-resource settings while maintaining good agreement with the conventional gravimetric uroflowmetry.

Conventional weight-based (gravimetric) uroflowmetry remains the established reference standard for uroflow assessment and offers automated flow-curve generation with high measurement accuracy. However, these systems generally require dedicated equipment, electrical power, maintenance, trained personnel, and attendance at a healthcare facility. In contrast, the present portable volumetric device uses controlled fluid outflow and chamber-based volume accumulation. While weight-based systems may provide greater automation and data integration, volumetric systems may offer potential advantages in portability, affordability, disposability, ease of transport, and applicability in resource-limited settings. The two approaches should therefore be viewed as complementary rather than competing technologies, with portable volumetric devices potentially expanding access to uroflowmetry outside conventional hospital environments.

The device may have potential future applications in tele-urology and remote patient monitoring wherein the report would be generated by the central processing unit after the patient has shared the pictures of the study unit after use. However, these applications were not evaluated in the present study, which was conducted entirely under supervised clinical conditions. Future studies are required to assess the device’s performance, usability, and patient compliance in real-world home-monitoring environments. If validated, such applications could facilitate longitudinal assessment of LUTS, postoperative follow-up, and treatment response monitoring while reducing the need for repeated hospital visits, and potentially supporting use in primary-care settings, rural healthcare facilities, and regions with limited access to conventional uroflowmetry equipment.

The present study additionally demonstrated strong positive correlation across all uroflowmetry variables, with Spearman correlation coefficients ranging from 0.799 to 0.963. Intraclass correlation analysis revealed excellent agreement for voided volume and good agreement for flow parameters.

Bland–Altman analysis showed minimal systematic bias and a narrow 95% limits of agreement, indicating strong concordance between the two methods. Qmax demonstrated slightly greater variability than voided volume, as reflected by the wider limits of agreement observed on Bland–Altman analysis. Despite this variability, the observed mean bias for Qmax was small (+0.6 mL/s), and agreement remained comparable to that reported for other portable uroflowmetry devices. Therefore, while individual Qmax values should always be interpreted within the broader clinical context, the study device demonstrated acceptable agreement with the conventional uroflowmetry for the assessment of peak flow. The simultaneous measurement design also minimized potential variability arising from separate voiding events and allowed direct comparison under identical physiological conditions. Although participants represented a broad age spectrum and both sexes, subgroup-specific agreement analyses were beyond the scope of the present study and warrant future investigation.

Limitations

The study was limited to two centers with supervised measurements, and the device was not evaluated in unsupervised home-monitoring conditions. Therefore, conclusions regarding home use and patient-operated deployment should be considered preliminary. Bench repeatability of the device was assessed during development; however, repeatability in patients was not specifically evaluated in the present study, as uroflowmetry parameters are known to exhibit physiological variability even within the same individual across repeated voids. Long-term performance was also not evaluated because the study device is intended for disposable or limited-reuse applications rather than prolonged repeated use. The population was predominantly male, and a formal subgroup analyses according to age and gender were not performed. Future studies should evaluate agreement across specific demographic groups to further establish generalizability.

CONCLUSION

The study device demonstrates good agreement with conventional uroflowmetry under supervised clinical conditions and may serve as a low-cost alternative method for uroflow assessment in settings where conventional electronic uroflowmetry is unavailable. Further large-scale multicenter studies, including evaluation in home-monitoring environments, are required before broader implementation can be recommended.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.