Etude des contrôles descendants de la douleur dans les rhumatismes inflammatoires au cours d'un traitement par biothérapie. L'étude RAPID

In inflammatory rheumatism (rheumatoid arthritis (RA) and spondyloarthritis (SpA)), pain intensity does not correlate with disease activity before or after well-conducted disease-modifying therapy. The hypothesis underlying our work was that this dissociation between pain and disease activity could be related to a dysfunction of the endogenous pain modulation systems.To test this hypothesis, we conducted a prospective, two-centre, routine care study in 100 patients with either RA or SpA, actively starting anti-TNF disease-modifying therapy, compared with 100 sex- and age-matched controls. The study of descending inhibitory controls was based on a conditioned pain modulation (CPM) protocol consisting of measuring the inhibition of pain evoked by a warm test stimulation induced by a heterotopic conditioning stimulation (immersion of the contralateral hand or foot in a cold water bath), before and then 3 and 6 months after the initiation of anti-TNF therapy.At baseline, the mean CPM effect, corresponding to the absolute value of the difference between the hot pain thresholds measured before and after conditioning, was significantly (p<0.0001) lower in patients (0.25°C ± 2.57) than in controls (2.79°C ± 2.31).Of the 87 patients who started anti-TNF therapy, 74 were reassessed at 6 months and the therapeutic response was considered at least moderate in 79.7% of them. The mean CPM effect was significantly (p<0.001) increased in the whole patient population, but significantly (p=0.04) less in patients (36.5%) with residual pain ≥ 4/10 at the end of follow-up (2.47°C ± 2.1) compared to patients without pain after treatment (3.25°C ± 2.7).This study showed that chronic pain associated with inflammatory rheumatisms is associated with a decrease in descending inhibitory controls and that the lack of restoration of these controls in about 36 % of patients after treatment was probably responsible for the persistence of pain.