title: Systemic inflammation and painful joint burden in osteoarthritis: a matter of sex?
abstract: We investigated the association between serum levels of C-reactive protein (CRP) and the extent of multijoint pain among individuals with hip/knee osteoarthritis (OA) and determined whether the association differs by sex.
  
  
  
  Serum CRP and cartilage oligomeric matrix protein (COMP) were determined by enzyme-linked immunosorbent assay (ELISA) in 189 individuals (101 female, 88 male) scheduled for total hip/knee arthroplasty for OA. Patients indicated on a homunculus all painful joints; a summed count was derived. A series of negative binomial regression models was used to investigate the cross-sectional association between painful joint count (outcome) and serum CRP concentrations, adjusting for age, sex, body mass index (BMI), comorbidity count and COMP. An interaction between sex and these biomarkers was tested.
  
  
  
  Mean age: 66 among women, 65 among men. Women had higher mean joint count (3.7 vs 2.5, P < 0.01; 4+ joint count reported by 37% women, 25% men). Median CRP concentration was higher in women (15.4 mg/l vs 9.3, P = 0.07). From adjusted analyses, the effects of both ln(CRP) and ln(COMP) were modified by sex (P < 0.05). Increasing ln(CRP) was associated with greater painful joint count among women, but not men.
  
  
  
  There may be a dose-response association between painful joint burden in OA and systemic inflammation, and it appears the association is sex-specific, which may in part explain inconsistent findings in the literature. Our results underline the importance of showing sex-specific associations in OA, especially when studying the influence of inflammation.
authors.affiliation: Krembil Research Institute and Arthritis Program, University Health Network, Canada; Institute of Health Policy, Management and Evaluation, University of Toronto, Canada; Orthopaedics, Department of Surgery, University of Toronto, Canada; Dalla Lana School of Public Health, University of Toronto, Canada. Electronic address: perrucci@uhnres.utoronto.ca.
authors.forename: A V
authors.initials: AV
authors.lastname: Perruccio
authors.affiliation: Krembil Research Institute and Arthritis Program, University Health Network, Canada; Rheumatology, Department of Medicine, University of Toronto, Canada; Rheumatology, Toronto Western Hospital, University Health Network, Canada. Electronic address: vchandra@uhnresearch.ca.
authors.forename: V
authors.initials: V
authors.lastname: Chandran
authors.affiliation: Krembil Research Institute and Arthritis Program, University Health Network, Canada; Dalla Lana School of Public Health, University of Toronto, Canada. Electronic address: dpower@uhnres.utoronto.ca.
authors.forename: J D
authors.initials: JD
authors.lastname: Power
authors.affiliation: Krembil Research Institute and Arthritis Program, University Health Network, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Canada. Electronic address: Mohit.Kapoor@uhnresearch.ca.
authors.forename: M
authors.initials: M
authors.lastname: Kapoor
authors.affiliation: Krembil Research Institute and Arthritis Program, University Health Network, Canada; Orthopaedics, Department of Surgery, University of Toronto, Canada; Orthopaedics, Toronto Western Hospital, University Health Network, Canada. Electronic address: Nizar.Mahomed@uhn.ca.
authors.forename: N N
authors.initials: NN
authors.lastname: Mahomed
authors.affiliation: Orthopaedics, Department of Surgery, University of Toronto, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Canada; Orthopaedics, Toronto Western Hospital, University Health Network, Canada. Electronic address: Rajiv.Gandhi@uhn.ca.
authors.forename: R
authors.initials: R
authors.lastname: Gandhi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018771:Arthralgia / Q000473:pathology*; D015415:Biomarkers / Q000097:blood; D015992:Body Mass Index; D002097:C-Reactive Protein / Q000032:analysis; D064236:Cartilage Oligomeric Matrix Protein / Q000097:blood; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007249:Inflammation / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000473:pathology*; D020370:Osteoarthritis, Knee / Q000473:pathology*; D012737:Sex Factors
chemical_list: D015415:Biomarkers; D064236:Cartilage Oligomeric Matrix Protein; D002097:C-Reactive Protein
keywords: C-reactive protein; Inflammation; Multijoint symptoms; Osteoarthritis; Sex