Discrepancies in assessment of patients with rheumatoid arthritis and secondary Sjogren's syndrome by DAS28-ESR and DAS28-CRP

Objectives: To investigate whether a difference exists between DAS28 from CRP and DAS28 from ESR in patients with rheumatoid arthritis (RA) and secondary Sjogren's syndrome (sSS). Material and methods: One group comprised patients with RA and sSS, the control group comprised patients with RA. The inclusion criteria for the RA and sSS group have been specified as follows: presence of at least one symptom of dryness, and also presence of anti-SS-A and anti-SS-B or at least focus score of one in biopsy. Results: The disease activity score 28 (DAS28) was assessed using both ESR and CRP in 60 patients with RA and sSS and 59 patients with RA alone. However, concordance between these two methods was good (Cohen's kappa coefficient kappa = 0.60, 95% CI: 0.45-0.75 in the first group and kappa = 0.71, 95% CI : 0.56-0.86 in the control group). In the group with RA and sSS, the mean value of DAS28-ESR = 5.2, whereas the mean value of DAS28-CRP = 4.7 (p < 0.0001). In the group with RA alone, mean DAS28-ESR = 4.7 while mean DAS28-CRP = 4.6; no significant difference was identified. Moreover, in RA patients with sSS, mean ESR = 39 mm/h compared with mean CRP at 25 mg/l. 79% of all patients demonstrated dysproteinaemia. There were connections between higher ESR and dysproteinaemia. In the control group there was no statistically significant difference between CRP and ESR. Conclusions: Both DAS28-ESR and DAS28-CRP are useful outcome measures in RA. However, in patients with RA and sSS, DAS28 should be evaluated based on CRP.