Reliability of urinary albumin, total protein, and creatinine assays after prolonged storage: The family investigation of nephropathy and diabetes

Rulan S. Parekh, W. H Linda Kao, Lucy A. Meoni, Eli Ipp, Paul L. Kimmel, Janine La Page, Carol Fondran, William C. Knowler, Michael J. Klag, R. C. Elston, S. Iyengar, K. Goddard, J. Olson, S. Ialacci, S. Edwards-Quade, A. Horvath, G. Jun, K. Kramp, M. Slaughter, E. ZaletelJ. R. Sedor, J. Schelling, A. Pickens, L. Humbert, L. Getz-Fradley, S. Adler, H. E. Collins-Schramm, H. Li, M. Pahl, Michael F Seldin, B. Walker, C. Garcia, J. Gonzalez, L. Ingram-Drake, L. Mead, T. Whitehead, J. Chester, R. L. Hanson, R. G. Nelson, J. Wolford, L. Jones, R. Juan, R. Lovelace, J. Loebel, C. Luethe, C. Pagliasotti, L. M. Phillips, J. Sewemaenewa, I. Sili, B. Waseta, M. F. Saad, S. Nicholas, X. Guo, J. Rotter, K. Taylor, Y. D I Chen, M. Budgett, F. Hariri, C. Muro, K. Ngo, P. Zager, V. Shah, M. Scavini, A. Bobelu, H. Abboud, N. Arar, R. Duggirala, B. S. Kasinath, R. Plaetke, M. Stern, C. Jenkinson, C. Goyes, V. Sartorio, T. Abboud, L. Hernandez, B. I. Freedman, D. W. Bowden, S. C. Satko, S. S. Rich, S. Warren, S. Viverette, G. Brooks, R. Young, M. Spainhour, O. Kohn, C. Brown, D. Leehey, G. Barone, D. Thornley-Brown, C. Jefferson, V. Turner, C. Winkler, M. W. Smith, M. Thompson, R. Hanson, B. Kessing, J. P. Briggs, R. Rasooly, D. Warnock, R. Chakraborty, G. M. Dunston, S. J. O'Brien, R. Spielman

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

Background and objectives: This study investigated the effect of long-term storage at -70°C on urinary albumin, protein, and creatinine measurements in the Family Investigation of Nephropathy and Diabetes, a multicenter study designed to identify genes for diabetic nephropathy. Design, setting, participants, & measurements: Spot urine samples were collected at eight centers and shipped overnight on ice packs to a central laboratory. Samples were aliquotted and frozen at -70°C for a median of 8 d before initial assay. As part of quality control procedures to determine interassay variability, 351 replicate samples were retrieved from storage at -70°C after a median storage time between original and quality control analyses of 126 d (range 28 to 869 d). Freezer time was characterized as the difference in days between the initial assay and quality control assay. Percentage difference [(quality control - original/original) × 100%] between samples was regressed on storage time and adjusted for original value, age, race, gender, hypertension, and diabetes. Results: After adjustment, freezer time per 30 d was associated with small decreases in percentage difference of urinary albumin (0.25%, P = 0.02), total protein (0.23%, P = 0.02), and albumin-to-creatinine ratio (0.34%, P = 0.001). Urinary creatinine levels were not affected by freezer time (P = 0.25). Conclusions: Measurements of urinary albumin, total protein, and albumin-to-creatinine ratio are minimally affected by storage at -70°C for approximately 2.5 yr. Prolonged storage results in small decreases of urinary albumin and protein that do not substantially affect phenotype classification of overt renal disease.

Original languageEnglish (US)
Pages (from-to)1156-1162
Number of pages7
JournalClinical Journal of the American Society of Nephrology
Volume2
Issue number6
DOIs
StatePublished - Nov 2007

ASJC Scopus subject areas

  • Nephrology
  • Transplantation
  • Epidemiology
  • Critical Care and Intensive Care Medicine
  • Medicine(all)

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    Parekh, R. S., Kao, W. H. L., Meoni, L. A., Ipp, E., Kimmel, P. L., La Page, J., Fondran, C., Knowler, W. C., Klag, M. J., Elston, R. C., Iyengar, S., Goddard, K., Olson, J., Ialacci, S., Edwards-Quade, S., Horvath, A., Jun, G., Kramp, K., Slaughter, M., ... Spielman, R. (2007). Reliability of urinary albumin, total protein, and creatinine assays after prolonged storage: The family investigation of nephropathy and diabetes. Clinical Journal of the American Society of Nephrology, 2(6), 1156-1162. https://doi.org/10.2215/CJN.01030207