Uroflow nomogram for healthy, 15-40 year old Indian men.

INTRODUCTION: Uroflowmetry is the objective method of measuring rate of urine flow. Nomograms are required to observe the change in flow rates at different voided volumes (VVs) and the use of which overcomes the limitation of referencing flow rates to any single VV. The purpose of the present study was to construct the Indian uroflow nomogram for adult healthy males between 15-40 years of age.
METHODS: A total of 1000 healthy males between 15 and 40 years of age were included in the study. Exclusion criteria were any urinary symptoms or urological intervention. Parameters analyzed statistically were age, peak flow rate (Qmax), average flow rate (Qavg), and VV. A nomogram was drawn for the fitted regression model.
RESULTS: The mean age was 27.26 ± 6.71 years. The mean Qmax, Qavg, and VV were 24.32 ± 3.50 ml/s, 9.45 ± 2.55 ml/s, and 420.93 ± 97.89 ml, respectively. The correlation between flow rates and VV was statistically significant, indicating that the higher the VV, the higher the flow rates. A negative significant correlation of Qmax with age was seen in our study. We observed a decline of Qmax by 1 ml/s/decade. The relationship of Qmax with VV is in linear progression up to 600 ml, and then it becomes a plateau and with higher VV it declined.
CONCLUSION: Qmax exhibits significant correlation with VV and age. A nomogram was constructed to attain normal reference values of flow rate over different VVs.

INTRODUCTION

Uroflowmetry is the objective method of measuring rate of urine flow; peak flow rate (Qmax), average flow rate (Qavg), and voided volume (VV) are important parameters recorded for interpretation.[12] It is an easy and noninvasive procedure.[1] It can be repeated easily and hence useful for diagnosis and monitoring treatment results.[12] Nomograms help to observe the change in flow rates at different VVs and their use overcomes the limitations of referencing flow rates to any single VV.[1] In addition, age has a significant impact on micturition. A nomogram in centile form was constructed to attain normal reference values of flow rates over different VVs in various age groups.[123456] Since flow rates may vary with populations, we constructed a uroflow nomogram for Indian men. We aimed to establish normal reference values of flow rates over wide range of VVs in healthy Indian men between 15 and 40 years of age, to evaluate the effects of age and VV over urinary flow parameters, and to construct a flow rate-VV nomogram in centile form.

METHODS

Institutional Ethical Committee approval was obtained prior to the commencement of the study. Between October 2013 and September 2015, 1000 healthy male individuals who accompanied patients visiting the urology outpatient department (OPD) were included in the study. Subjects with a history of neurological disease, psychological disease, diabetes mellitus, urological disease (lower urinary tract symptoms, urinary tract infection, bladder and urethral stones, bladder cancer, meatal stenosis, etc.,) and those with ongoing medical treatment that affected lower urinary system function (such as anticholinergics, alpha-blockers, 5-alpha reductase inhibitors, alpha stimulants, and antibiotics) were excluded from the study. Informative and interactive sessions for the subjects were taken prior to the study and written informed consent was obtained from each participant who was willing for the study. Relevant history and clinical examination were performed to evaluate the health of the participant.

Uroflowmetry was performed using Solar urodynamic apparatus (Medical Measurements System, Enschede, The Netherlands) in the urology OPD at a separate room to ensure complete privacy. Participants were instructed to present with a full bladder (holding urine), and the test was performed when they had the normal sensation to urinate. They were asked to void in their usual way. The test was explained to all the participants before the session. Uroflowmetry was performed using a gravimetric uroflowmeter. The uroflowmeter was calibrated at regular intervals to ensure consistency using an internal self-calibration program. The parameters evaluated were age, Qmax, Qavg, and VV.

At the end of the study, a statistical analysis was done. We used Karl Pearson's correlation coefficient to find the correlation between the variables. We used linear regression model for Qmax and Qavg as responses with age and VV as independent variables. A nomogram was drawn for the fitted regression model. The softwares used were R - 3.2.1, Minitab 16, and Stata. (R is free software environment for Statistical computing ©The R Foundation USA, Minitab Ltd Brandon Court Conventry CV3 2TE United Kingdom and Stata Corp LP Texas USA.)

RESULTS

The result of different parameters of the study group is shown in Table 1. The mean age was 27.26 ± 6.71 years. The mean Qmax, Qavg, and VV were 24.32 ± 3.50 ml/s, 9.45 ± 2.55 ml/s, and 420.93 ± 97.89 ml, respectively. The correlation of Qmax and Qavg with VV was statistically significant (Pearson's correlation coefficient r = 0.31 and r = 0.18, P < 0.0001, respectively). The correlation between Qmax and age was found to be significant (Pearson's correlation coefficient r = −0.21, P < 0.0001), but Qavg was not significantly correlated with age (Pearson's correlation coefficient r = −0.013 and P = 0.681). There was decline of Qmax observed by 1 ml/s/decade (F = 20.832 and P < 0.0001; Table 2). Qmax increases with VV up to 600 ml, followed by plateau phase up to 750 ml, and above 750 ml, decline in Qmax was observed (F = 26.381 and P < 0.0001) as shown in Table 3. The regression equation for peak and Qavg based on VV and age is given in Box 1. The nomogram plotted in centile form for Qmax and VV is shown in Figure 1.

Table 1

Parameters statistics in study group

Table 2

Peak flow rate in relation to age group

Table 3

Peak flow rate in relation to voided volume

Box 1

Regression equation for peak and Qavg

Figure 1

Uroflowmetry nomogram of peak flow rate in 15–40 years old male population in India

DISCUSSION

Nomograms have been constructed to attain normal reference values of flow rates over different VVs in centile form.[1] Siroky et al. were among the first to develop such a nomogram.[3] The mean Qmax of healthy adult males between 15 and 40 years of age in our study was 24.32 ± 3.50 ml/s. The mean Qmax of our study was greater than the study done by Kumar et al. on Indian population but lower than the Austrian and Thai population as shown in Table 4.[145] The disparity of the results maybe due to difference in age groups. In our study, healthy males between 15 and 40 years of age were included in the study while the age group of healthy male population in the study of Kumar et al. was 16–50 years.[1] However, the Austrian study had included younger males of 18 years while in the Thai population study, males between 18 and 30 years of age were included.[45]

Table 4

Peak flow rate in different studies

The correlation between Qmax and Qavg with VV was found statistically significant (Pearson's correlation coefficient r = 0.31 and r = 0.18, P < 0.0001, respectively), indicating that the higher the VV, the higher the flow rates, as also seen in various studies.[136] A negative but significant correlation of Qmax with age was seen in our study (Pearson's correlation coefficient r = −0.21, P < 0.0001); similar negative correlations between Qmax and age were observed in other studies.[156] We observed the decline of Qmax by 1 ml/s/decade (F = 20.832 and P < 0.0001), and similar results were reported by Drach et al. in their study.[7] Kumar et al. also noted a decline of 1 ml/s/decade in Qmax in their study.[1]

The relationship of Qmax with VV is in linear progression up to 600 ml, and then it becomes a plateau, with higher VV it declines (F = 26.381 and P < 0.0001). A similar correlation was reported by Kumar et al. at 700 ml.[1] A similar study was conducted by Pernkopf et al., who found a positive correlation of VV and Qmax up to 350 ml, from 350 to 550 ml, Qmax remains same and a decrease in Qmax after 550 ml.[4] Bross et al. in their investigations proved experimentally a decrease of intravesical pressure at supraphysiological volumes.[8]

CONCLUSION

Qmax and Qavg exhibit significant positive correlation with VV while age is inversely proportional to Qmax and Qavg in healthy Indian males between 15 and 40 years of age. A nomogram was constructed to attain normal reference values of flow rate over different VVs.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.