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Age Adjustment Corrects for Apparent Differences in Erythrocyte Sedimentation Rate and C-Reactive Protein Values at the Onset of Seropositive Rheumatoid Arthritis in Younger and Older Patients
VEENA K. RANGANATH, DAVID A. ELASHOFF, DINESH KHANNA, GRACE PARK, JAMES B. PETER, and HAROLD E. PAULUS, for the WESTERN CONSORTIUM of PRACTICING RHEUMATOLOGISTS
ABSTRACT.
Objective. To evaluate the effect of age adjustment on baseline erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) in patients with late-onset rheumatoid arthritis (LORA, age ≥ 55 yrs) and younger-onset RA (YORA, age < 55 yrs) in a cohort with early, rheumatoid factor (RF) positive RA that has not received disease modifying antirheumatic drugs (DMARD). Methods. In an ongoing prospective cohort study of 263 patients with seropositive RA who were enrolled within 14 months of symptom onset, baseline assessments included ESR, CRP, tender and swollen joint counts, and functional status. Westergren ESR determinations were performed in the rheumatologist's office or in a local laboratory using appropriate methods. CRP were performed at the Specialty Laboratories in Santa Monica, CA, using Behring nephelometry. Percentages of patients with greater than the upper limit of normal (ULN) laboratory values using both age-unadjusted and age-adjusted ESR and CRP values were determined. The late-onset and younger-onset RA patients were compared using Wilcoxon rank-sum and chi-square tests. Results. At study entry, both the YORA and LORA patients had comparable symptom duration, disease activity scores, tender and swollen joint counts, and Health Assessment Questionnaire values. RF, CRP, and ESR were significantly higher (p < 0.05) in LORA patients. Although the percentages of patients with age-unadjusted ESR and CRP above ULN were higher in LORA patients, the percentages exceeding the age-adjusted ULN did not differ significantly between the YORA and LORA groups. Conclusion. In patients with late-onset and younger-onset RA with similar disease duration and severity, the apparent discrepancy in elevation of both the baseline ESR and CRP disappears after age-adjustment. (J Rheumatol 2005;32:1040-2) Key Indexing Terms:
EARLY RHEUMATOID ARTHRITIS
From the Division of Rheumatology, Department of Biostatistics and School of Public Health, Geffen School of Medicine at UCLA; VA Greater Los Angeles Healthcare System, Los Angeles, California; the Division of Immunology, Department of Medicine, University of Cincinnati, Cincinnati, Ohio; and Specialty Laboratories Inc., Santa Monica, California, USA. V.K. Ranganath, MD, Clinical Rheumatology Fellow; D.A. Elashoff, PhD, Assistant Professor of Biostatistics and Nursing; D. Khanna, MD, Assistant Professor of Medicine; G. Park, MPH; J.B. Peter, MD, PhD; H.E. Paulus, MD, Professor of Medicine, Department of Medicine, UCLA. The Western Consortium of Practicing Rheumatologists: Robert Shapiro, Maria W. Greenwald, H. Walter Emori, Fredrica E. Smith, Craig W. Wiesenhutter, Charles Boniske, Max Lundberg, Anne MacGuire, Jeffry Carlin, Robert Ettlinger, Michael H. Weisman, Elizabeth Tindall, Karen Kolba, George Krick, Melvin Britton, Rudy Greene, Ghislaine Bernard Medina, Raymond T. Mirise, Daniel E. Furst, Kenneth B. Wiesner, Robert F. Willkens, Kenneth Wilske, Karen Basin, Robert Gerber, Gerald Schoepflin, Marcia J. Sparling, George Young, Philip J. Mease, Ina Oppliger, Douglas Roberts, J. Javier Orozco Alcala, John Seaman, Martin Berry, Ken J. Bulpitt, Grant Cannon, Gregory Gardner, Allen Sawitzke, Andrew Lun Wong, Daniel O. Clegg, Timothy Spiegel, Wayne Jack Wallis, Mark Wener, and Robert Fox. Address reprint requests to Dr. H.E. Paulus, Division of Rheumatology, Department of Medicine, Rehabilitation Center, Room 32-59, 1000 Veteran Avenue, UCLA School of Medicine, Los Angeles, CA 90095-1670. E-mail: hpaulus@mednet.ucla.edu Accepted for publication February 5, 2005. |