A prospective study of protein excretion using short-interval timed urine collections in patients with lupus nephritis - PubMed (original) (raw)

Comparative Study

. 2009 Dec;76(12):1284-8.

doi: 10.1038/ki.2009.344. Epub 2009 Sep 16.

Affiliations

Comparative Study

A prospective study of protein excretion using short-interval timed urine collections in patients with lupus nephritis

Derek M Fine et al. Kidney Int. 2009 Dec.

Abstract

The 24-h urine protein-to-creatinine ratio is the gold standard in evaluating proteinuria in lupus nephritis; however, the urine collection is inconvenient to the patient. Random spot urine protein-to-creatinine ratios, although convenient, have poor agreement with the 24-h ratios in these patients. Here, we sought to define a timed collection interval providing accurate and precise data and patient convenience. Urine from 41 patients, in 2 medical centers, with biopsy-proven lupus nephritis was collected at 6-h intervals for 24 h. The protein-to-creatinine ratio of each short collection was then compared with that of a 24-h collection made by combining the 6-h samples. A first morning void and spot urine samples were collected before and after the 24-h collection, respectively. There was significant diurnal variation with peak proteinuria at 6-12 h and nadir at 18-24 h. Each 6-h collection showed excellent correlation and concordance with the 24-h protein-to-creatinine ratio, but the 12-24-h interval had the best agreement. In contrast to the random spot urines, the first morning void also had excellent correlation and concordance, but underestimated the 24-h protein-to-creatinine ratio. Our study shows that a 12-h overnight urine collection is the best surrogate, with excellent agreement with the 24-h protein-to-creatinine ratio, and it is convenient for patients. There was little variability between centers, an important feature for clinical trials.

PubMed Disclaimer

Conflict of interest statement

DISCLOSURE

All the authors declared no conflict of interests.

Figures

Figure 1

Figure 1. Collection timeline for interval collections

Spot 0 (SP0) was first morning urine and spot 2 (SP24) was obtained after the 24-h urine collection was completed. Note that for Hopkins lupus cohort (HLC), SP24 was obtained as the second morning void and for Ohio SLE Study (OSS), as a random spot collection. SLE, systemic lupus erythematosus.

Figure 2

Figure 2. Diurnal variation of protein excretion

Interval protein/creatinine (P/C) ratios were divided by their corresponding 24-h P/C ratios for the indicated intervals. SP0 represents the first morning void. The middle bar represents the mean ratio, and the top and bottom bars represent ±2 standard errors of the mean. *P<0.001 versus 18–24-h interval.

Figure 3

Figure 3. Variability of interval protein/creatinine (P/C) ratio declines as the duration of the interval approaches 24 h

Box-and-whisker plots of individual interval P/C ratios divided by their corresponding 24-h P/C ratio. Boxes represent the interquartile range. Whisker lengths represent up to 1.5 times the interquartile range. Outliers beyond the whiskers are shown with open circles.

Figure 4

Figure 4. Correlation of 6- and 12-h protein/creatinine (P/C) ratio with 24-h P/C ratio

The dashed line represents the line of perfect concordance (45° line); the solid line is the best-fit regression.

Similar articles

Cited by

References

    1. Austin HA. Clinical evaluation and monitoring of lupus kidney disease. Lupus. 1998;7:618–621. - PubMed
    1. Balow JE. Clinical presentation and monitoring of lupus nephritis. Lupus. 2005;14:25–30. - PubMed
    1. Contreras G, Pardo V, Cely C, et al. Factors associated with poor outcomes in patients with lupus nephritis. Lupus. 2005;14:890–895. - PubMed
    1. Renal Disease Subcommittee of the American College of Rheumatology Ad Hoc Committee on Systemic Lupus Erythematosus Response Criteria. The American College of Rheumatology response criteria for proliferative and membranous renal disease in systemic lupus erythematosus clinical trials. Arthritis Rheum. 2006;54:421–432. - PubMed
    1. Christopher-Stine L, Petri M, Astor BC, et al. Urine protein-to-creatinine ratio is a reliable measure of proteinuria in lupus nephritis. J Rheumatol. 2004;31:1557–1559. - PubMed

Publication types

MeSH terms

Substances

Grants and funding

LinkOut - more resources