gms | German Medical Science

Introduction: A fast response to non-steroidal anti-inflammatory drugs (NSAIDs) is an important finding in the evaluation of clinical findings within the items comprising the ASAS classification criteria but also for the treatment decision for escalation to a bDMARD in axSpA patients.However, the differentiation of NSAID responses between axSpA patients and degenerative or unspecific back pain is still unclear. We aimed to study the differences in the velocity and magnitude of NSAID response velocity in patients with established bDMARD naïve axSpA vs. patients with other, non-inflammatory reasons of back pain.

Methods: Patients with axSpA or with degenerative or unspecific back pain presenting due to high levels of back pain (NRS≥4/10) were consecutively recruited. Upon study inclusion, patients were treated with the maximum possible dose of an NSAID. Assessment of response was performed using a standardized questionnaire after 2, 6, 12, 24, 36, 48 hours and after 1, 2 and 4 weeks. Any NSAID response was defined as improvement of pain >2/10 points and a good response to NSAIDs as an improvement >50% from the initial status.

Results: A total of 68 axSpA patients, 107 with degenerative and 58 with unspecific back pain were included. The mean age was 42.7±10.7, 51.2±11.3, and 45.8±10.0 years, the main symptom duration 15.1±11.1, 16.1±12.6, and 11.9 ±10.1 years and the proportion of males was 57.4%, 19.6%, and 19.0% respectively. Inflammatory back pain was reported by 42 (75%), 48 (57.8%), and 29 (60.4%) patients and the mean pain score was 6.2±2.3, 6.7±1.8, and 6.2±1.8, respectively. In axSpA, the mean BASDAI score was 5.5±1.8 and BASFI 4.5±2.5. There was no difference in the cumulative response to NSAIDs between all three diagnoses, with an overall proportion of 27%-30% of patients showing improvement. However, better but not faster responses were found for the subgroups of nr-axSpA patients (Figure 1 [Fig. 1]) and for the male patients in the entire axSpA group, while axSpA patients with increased CRP value showed lower rates of response as compared to non-inflammatory back pain. All other subanalyses did not reveal any differences between axSpA patients and other non-inflammatory reasons of back pain.

Conclusion: In this prospective evaluation, the generally proposed better response of axSpA patients to treatment with high doses of NSAIDs as compared with non-inflammatory back pain was not confirmed, although the overall rate of responders was similar to previously reported rates. On the other hand, better responses were found in patients treated in the early (nr-axSpA) stage and in male patients. axSpA patients with increased CRP values showed lower rates of response.