[Pattern of serum cytokines in patients with rheumatoid artritis according to PPD reactivity]

We demonstrated, in a recently published study, far more PPD negative reactivity among patients who had RA (70%) than among controls (30%). To evaluate the hypothesis that different response to PPD in RA patients is associated with different profiles of serum cytokines, we compared the serum levels of IL-2, IL-4, IL-6, IL-10, TNF alpha and IFN gamma from PPD negative and PPD positive RA patients. We also evaluated any correlations between serum cytokines and RA activity.

Forty RA patients and 21 controls were enrolled. Those with an induration < 5mm were considered as negative and those with ≥ 5mm as positive PPD. Disease activity was calculated using DAS28. Plasma levels of cytokines were determined using the multiplex BD TM Cytometric Bead Array Kit Assay.

Of the RA patients, 27 (67.5%) had negative reaction to PPD and 13 (32.5%) a positive reaction to PPD. There was no statistical difference in sex profile, age or activity index between both negative and positive PPD RA patients. There was no significant difference in all the cytokines measured between PPD positive and PPD negative RA patients. Index activity show a positive correlation with IFN gamma (r = 0.433; p = 0.005) and IL-6 (r = 0.325; p = 0.041) in RA patients.

Positive and negative tuberculin RA patients seem to show a similar cytokine serum profile.