Observational Study
Copyright ©The Author(s) 2023. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Nephrol. Dec 25, 2023; 12(5): 159-167
Published online Dec 25, 2023. doi: 10.5527/wjn.v12.i5.159
The correlation of spot urinary protein-to-creatinine ratio with 24-h urinary protein excretion in various glomerulopathies
Amber Raza, Syed Haider Nawaz, Rahma Rashid, Ejaz Ahmed, Muhammed Mubarak
Amber Raza, Ejaz Ahmed, Department of Nephrology, Sindh Institute of Urology and Transplantation, Sindh, Karachi 74200, Pakistan
Syed Haider Nawaz, Rahma Rashid, Muhammed Mubarak, Department of Pathology, Sindh Institute of Urology and Transplantation, Sindh, Karachi 74200, Pakistan
Author contributions: Raza A and Ahmed E contributed equally to this work; Raza A, Nawaz SH, Rashid R, Ahmed E, and Mubarak M designed the research study; Raza A, Nawaz SH and Rashid R performed the research; Raza A, Ahmed E, and Mubarak M analyzed the data and wrote the manuscript; All authors have read and approved the final manuscript.
Institutional review board statement: The study was reviewed and approved by the Sindh Institute of Urology and Transplantation (Pakistan).
Informed consent statement: All study participants, or their legal guardian, provided informed written consent prior to study enrollment.
Conflict-of-interest statement: There are no conflicts of interest to report.
Data sharing statement: The dataset and related documents are available from the corresponding author at [dramber88@gmail.com]. Consent was not obtained but the presented data are anonymized and risk of identification is low.
STROBE statement: The authors have read the STROBE Statement-checklist of items, and the manuscript was prepared and revised according to the STROBE Statement-checklist of items.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Muhammed Mubarak, MD, Professor, Department of Pathology, Sindh Institute of Urology and Transplantation, Chand Bibi Road, DFMC, Sindh, Karachi 74200, Pakistan. drmubaraksiut@yahoo.com
Received: August 5, 2023
Peer-review started: August 5, 2023
First decision: September 19, 2023
Revised: September 21, 2023
Accepted: October 23, 2023
Article in press: October 23, 2023
Published online: December 25, 2023
Abstract
BACKGROUND

Proteinuria is an important and well-known biomarker of many forms of kidney injury. Its quantitation is of particular importance in the diagnosis and management of glomerular diseases. Its quantification can be done by several methods. Among these, the measurement of 24-h urinary protein excretion is the gold standard method. However, it is cumbersome, time-consuming, and inconvenient for patients and is not completely foolproof. Many alternative methods have been tested over time albeit with conflicting results. Among the latter, the measurement of urine protein-to-creatinine ratio (uPCR) in single-voided urinary samples is widely used. The majority of studies found a good correlation between uPCR in single urine samples with 24-h urinary protein estimation, whereas others did not.

AIM

To investigate the correlation of spot uPCR with 24-h urinary protein estimation in patients suffering from different forms of glomerulopathies at a single large-volume nephrological center in Pakistan.

METHODS

This cross-sectional, observational study was conducted at the Department of Nephrology, Sindh Institute of Urology and Transplantation, Karachi, Pakistan from September 2017 to March 2018. All newly presenting adult patients with proteinuria who were being investigated for suspected glomerulonephritis and persistent proteinuria with ages between 18 to 60 years were enrolled. All patients were given detailed advice regarding 24-h urine collection starting at 7:00 AM for total protein and creatinine excretion estimations. A spot urine sample was collected the next day at the time of submission of a 24-h urine sample for measuring uPCR along with a blood sample. The data of patients were collected in a proforma. SPSS version 20.0 was used for statistical analysis.

RESULTS

A total of 157 patients were included. Their mean age was 30.45 ± 12.11 years. There were 94 (59.8%) males and 63 (40.2%) females. The mean 24-h urinary protein excretion was 3192.78 ± 1959.79 mg and the mean spot uPCR was 3.16 ± 1.52 in all patients. A weak but significant correlation was observed between spot uPCR and 24-h urinary protein excretion (r = 0.342, P = 0.01) among all patients. On subgroup analysis, a slightly better correlation was found in patients older than 47 years (r = 0.78), and those with body mass index > 25 kg/m2 (r = 0.45). The Bland and Altman's plot analysis comparing the differences between spot uPCR and 24-h protein measurement also showed a wide range of the limits of agreement between the two methods.

CONCLUSION

Overall, the results from this study showed a significant and weakly positive correlation between spot uPCR and 24-h urinary protein estimation in different forms of glomerulopathies. The agreement between the two methods was also poor. Hence, there is a need for careful interpretation of the ratio in an unselected group of patients with kidney disease.

Keywords: Glomerulopathies, 24-h proteinuria, Spot urinary protein-to-creatinine ratio, Correlation, Proteinuria, Agreement

Core Tip: The quantitation of proteinuria is of particular importance in the diagnosis and management of glomerulonephritides. The measurement of 24-h urinary protein excretion is the gold standard. However, it is cumbersome, time-consuming, and inconvenient for patients. The measurement of urine protein-to-creatinine ratio (uPCR) is the most popular alternative. Numerous studies have been conducted on the correlation of these two methods with conflicting results. We assessed the correlation and the degree of agreement between the two methods. We conclude that uPCR shows poor correlation and poor agreement with 24-h proteinuria. It must be interpreted with caution in an unselected group of glomerulopathies.