title: 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.
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 > or = 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Division of Rheumatology, Department of Biostatistics and School of Public Health, Geffen School of Medicine at UCLA, Los Angeles, California 90095-1670, USA.
authors.forename: Veena K
authors.initials: VK
authors.lastname: Ranganath
authors.forename: David A
authors.initials: DA
authors.lastname: Elashoff
authors.forename: Dinesh
authors.initials: D
authors.lastname: Khanna
authors.forename: Grace
authors.initials: G
authors.lastname: Park
authors.forename: James B
authors.initials: JB
authors.lastname: Peter
authors.forename: Harold E
authors.initials: HE
authors.lastname: Paulus
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000097:blood* / Q000503:physiopathology; D001799:Blood Sedimentation; D002097:C-Reactive Protein / Q000032:analysis*; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires
chemical_list: D002097:C-Reactive Protein