Background It is important to study new potential markers of response to treatment in rheumatoid arthritis (RA), because up to 40% patients don't achieve remission even using biological therapy. DNAse activity of the blood serum and antinuclear antibody may be useful in this context. Changes of serum DNase activity in the RA treatment by biological agents previously have been not investigated.

Objectives The aim of this work is to study the dynamics clinical and laboratory parameters, DNAse serum activity and ANA during the RA treatment by infliximab (INF) and assess the prognostic potential of them in prediction of response to INF.

Methods 24 RA patients were involved in the study. All patients fulfilled the EULAR/ACR 2010 RA criteria. 22/24 patients received 6 infusions of INF at a dose of 3 mg/kg according to standard protocol: at 0th, 2th, 6th and then every 8 week. 2/24 patient received 4 infusions of INF. All patients received synthetic DMARDs therapy by metotrexate (10–17,5 mg weekly), 18/24 patients received glucocorticoids (methylprednisolone 4–8 mg daily) and non-steroidal anti-inflammatory drugs. Prior to treatment by INF patients did not receive any biological agents. All patients had high disease activity before INF treatment (DAS28<5,1).

ANA determination was performed by indirect immunofluorescence on Hep-2 cells using digital system AKLIDES. ANA was measured in serum samples before 1st INF administration, at 22–30 weeks after the 1st INF administration.

To determine the DNAse activity of serum the method of rivanol clot was used. DNase activity was measured in serum samples before 1st INF administration, at 6 weeks after the 1st INF administration, at 30 week of treatment.

Results At week 30, ACR70 improvement reached 5/22 of the patients, ACR50 - 10/22 of the patients, ACR20 – 4/24 of patients.

At 30 weeks of treatment by INF 2/22 of patients achieved remission (SDAI<3,3), 10/22 - a low disease activity (3,3 <SDAI ≤11).

13/24 patients were ANA-positive before INF treatment, 12/22 - after 24 weeks of treatment.

Levels of serum DNase activity did not differ before and during the INF treatment (p>0,05).

For assessment prognostic value of laboratory signs for INF response prediction logistic regression was used. Prognostic model, which included changes in ANA (Δ ANA) and DNAse serum activity level (Δ DNAse serum activity), anti-CCP- and RF-negativity was better (p=0,02) (area under ROC-curve =1,0; 95% CI 0,844–1,00 p=0,0001) than the model, which included only anti-CCP- and RF-negativity (area under ROC-curve =0,795; 95% CI 0,597–0,924, p=0,0141).

Conclusions The study confirmed the efficacy of RA treatment by INF for anti-CCP and RF negative patients. DNAse serum activity and ANA may be used as additional prognostic biomarker of INF response. For the assessment DNAse activity as marker of response to therapy is needed futher investigations with more number of patients.

Disclosure of Interest None declared