OBJECTIVE: To evaluate the 24-hour urine protein-to-creatinine (U pr:cr) ratio compared to 24-h urine total protein excretion as a measure of proteinuria in patients with lupus nephritis. METHODS: Proteinuria in 8 patients with lupus nephritis treated with cyclophosphamide was monitored by total protein excretion and U pr:cr ratio in 24-h urine collections. A median of 16 measurements per patient were collected over a median of 47 months. Adequacy of the 24-h collection was assessed by comparing total urine creatinine to the predicted creatinine. Collections in which the difference between the predicted 24-h urine creatinine and the measured 24-h urine creatinine was greater than or equal to 20% were defined as inadequate collections. RESULTS: Timed 24-h urine collections were frequently inadequate (30.2% of total collections were under-collections, while 14.3% were over-collections). We found 87.5% of patients had at least one under-collection whereas 75% had at least one over-collection. Correlations between total protein and U pr:cr ratio for individual patients ranged from 0.87 to 0.99 (mean 0.95). For the entire sample, the correlation (R2 = 0.89) of total urine protein to Upr:cr ratio was excellent. Excluding the 38 under-collections led to improvement in the overall correlation (0.94). Excluding the 18 over-collections led to a correlation of 0.89. Excluding both under-collections and over-collections led to a correlation of 0.94. CONCLUSION: In patients with lupus nephritis, the 24-h U pr:cr ratio is highly correlated with the 24-h urine protein excretion when the collections are adequate. The error of the estimate is higher when collections are poor.
OBJECTIVE: To evaluate the 24-hour urine protein-to-creatinine (U pr:cr) ratio compared to 24-h urine total protein excretion as a measure of proteinuria in patients with lupus nephritis. METHODS:Proteinuria in 8 patients with lupus nephritis treated with cyclophosphamide was monitored by total protein excretion and U pr:cr ratio in 24-h urine collections. A median of 16 measurements per patient were collected over a median of 47 months. Adequacy of the 24-h collection was assessed by comparing total urine creatinine to the predicted creatinine. Collections in which the difference between the predicted 24-h urine creatinine and the measured 24-h urine creatinine was greater than or equal to 20% were defined as inadequate collections. RESULTS: Timed 24-h urine collections were frequently inadequate (30.2% of total collections were under-collections, while 14.3% were over-collections). We found 87.5% of patients had at least one under-collection whereas 75% had at least one over-collection. Correlations between total protein and U pr:cr ratio for individual patients ranged from 0.87 to 0.99 (mean 0.95). For the entire sample, the correlation (R2 = 0.89) of total urine protein to Upr:cr ratio was excellent. Excluding the 38 under-collections led to improvement in the overall correlation (0.94). Excluding the 18 over-collections led to a correlation of 0.89. Excluding both under-collections and over-collections led to a correlation of 0.94. CONCLUSION: In patients with lupus nephritis, the 24-h U pr:cr ratio is highly correlated with the 24-h urine protein excretion when the collections are adequate. The error of the estimate is higher when collections are poor.
Authors: Michelle Petri; Ana-Maria Orbai; Graciela S Alarcón; Caroline Gordon; Joan T Merrill; Paul R Fortin; Ian N Bruce; David Isenberg; Daniel J Wallace; Ola Nived; Gunnar Sturfelt; Rosalind Ramsey-Goldman; Sang-Cheol Bae; John G Hanly; Jorge Sánchez-Guerrero; Ann Clarke; Cynthia Aranow; Susan Manzi; Murray Urowitz; Dafna Gladman; Kenneth Kalunian; Melissa Costner; Victoria P Werth; Asad Zoma; Sasha Bernatsky; Guillermo Ruiz-Irastorza; Munther A Khamashta; Soren Jacobsen; Jill P Buyon; Peter Maddison; Mary Anne Dooley; Ronald F van Vollenhoven; Ellen Ginzler; Thomas Stoll; Christine Peschken; Joseph L Jorizzo; Jeffrey P Callen; S Sam Lim; Barri J Fessler; Murat Inanc; Diane L Kamen; Anisur Rahman; Kristjan Steinsson; Andrew G Franks; Lisa Sigler; Suhail Hameed; Hong Fang; Ngoc Pham; Robin Brey; Michael H Weisman; Gerald McGwin; Laurence S Magder Journal: Arthritis Rheum Date: 2012-08
Authors: Derek M Fine; Martina Ziegenbein; Michelle Petri; Ernest C Han; Alison M McKinley; Jerry W Chellini; Haikady N Nagaraja; Kathryn A Carson; Brad H Rovin Journal: Kidney Int Date: 2009-09-16 Impact factor: 10.612