Peptidyl-arginine deiminase-type IV as a diagnostic and prognostic marker in rheumatoid arthritis patients

Aim of the work

To measure serum peptidyl arginine deiminase (PADI4) enzyme level in rheumatoid arthritis (RA) patients and to assess its role in diagnosis and monitoring patient improvement.

Patients and methods

The study included 31 RA patients and 10 age and sex matched healthy controls. Serum PADI4 and anti-cyclic citrullinated peptide (anti-CCP) were measured. Disease activity score (DAS28) was calculated. Patients were followed-up at 3 months with measurement of serum PADI4, anti-CCP and DAS28.

Results

Mean age of the patients was 42.4?±?7.8 years, female:male?=?5.2:1 and disease duration 8.1?±?5.4 years. The DAS28 was 5?±?1.2 and modified health assessment questionnaire (MHAQ) was 0.8?±?0.6. Mean anti-CCP (129.3?±?74.8?ng/ml) and PADI-4 levels (532.9?±?240.9?pg/ml) in patients were significantly higher than in controls (8.4?±?4.4?ng/ml and 156?±?31?pg/ml respectively; p?<?0.001 both). At a cut-off value?≥?250?pg/ml, PADI4 was highly diagnostic for RA (sensitivity 90.3%, specificity 100%; area under curve?=?0.97 with no significant difference from anti-CCP at a cut-off of 15 ng/ml (sensitivity 93.5%, specificity 100%; AUC ?=?0.99). Serum PADI4 level showed a significant correlation with DAS28 (r?=?0.49, p?=?0.047). At follow up (n?=?20), no significant difference in PADI4, anti-CCP level or DAS28 scores was found but changes in serum PADI4 level significantly correlated with changes in DAS28 (r?=?0.82, p?<?0.001). Mean serum PADI4 level was significantly lower in improved patients (184.4?±?10.2?pg/ml) compared to unimproved (563.3?±?251.9?pg/ml, p?<?0.001).

Conclusion

Serum PADI4 was diagnostic for RA and comparable with anti-CCP. It correlated with disease activity and could be a promising follow up marker of remission.