Abstract
Background The host inflammatory response against infection is characterized by leukocytosis, and the release of cytokines and acute phase proteins. However, routine inflammatory markers are not always elevated in systemic rheumatic diseases (SRD). Here, we aimed to systematically evaluate and compare the clinical implications of common inflammatory markers in systemic rheumatic diseases (SRDs). Methods We investigated the profiles of erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and white blood cell (WBC) count in treatment-naïve patients with SRDs, osteoarthritis and pneumonia diagnosed at Seoul National University Hospital during 2004-2016. SRDs included rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), ankylosing spondylitis (AS), systemic sclerosis (SSc), idiopathic inflammatory myopathy (IIM) and adult onset of Still disease (AOSD). Associations between inflammatory markers were evaluated using Pearson’s correlation and regression analysis. Differences between correlations were compared using Steiger’s z-test. Receiver operating characteristic (ROC) curve analysis was performed to examine the predictive value of inflammatory markers for SRD diagnosis. Results We identified 1191 patients with SRDs, osteoarthritis and pneumonia. Leukocytosis was present in <15% SRD patients. There was marked variability in ESR and CRP levels among different SRDs. The highest mean CRP levels (mean ± SD, mg/dL) were observed in those with AOSD (11.3±7.9), followed by RA (2.0±3.3), IIM (1.8±3.5), SLE (1.5±3.1), SSc (0.6±1.3) and AS (0.08±0.1). Mean ESR (mm/hr) was also highest in AOSD (71.2±31.0), followed by SLE (47.3±34.2), RA (45.5±30.6), IIM (40.8±24.8) and SSc (27.8±26.0). All SRDs showed significant positive correlations between ESR and CRP: greatest in RA (r=0.53, p<0.001) and weakest in SLE (r=0.20, p=0.03). WBC correlated weakly with CRP but not with ESR in most SRDs. While the AUC for WBC count (0.54-0.68) was less than that of ESR or CRP, the AUC for ESR and CRP (0.69-0.86) were similar in SRD. The optimal cuff-off values for inflammatory markers predicting SRD were within or slightly above the normal limit. Conclusions Unlike acute infection, ESR, CRP and WBC count are not always elevated in treatment-naïve patients with SRD. Thus, common inflammatory markers have limited value for diagnosis and assessment of disease activity of SRD.
The PTPN22 R620W polymorphism is not associated with systemic rheumatic diseases in South Africans
