Background/Purpose: a) To evaluate the impact of the number of comorbidities on the outcome measures after two years of follow-up in patients with ankylosing spondylitis (AS) and b) to determine whether the number of comorbidities influences the retention rate to the first anti-TNF alpha.

Methods: Observational and prospective study during 2 years of follow-up that includes a subgroup of 749 patients with AS (REGISPONSER-AS) from the REGISPONSER study (Spanish Rheumatology Spondyloarthritis Registry). The patients were divided into three groups according to the number of comorbidities at baseline (0, 1 or ³2 comorbidities). The Patient Reported Outcomes (PROs) evaluated were the Global VAS, BASDAI, ASDAS, BASFI and the mental and physical components from the SF12 questionnaire. Linear regression models were performed using the PROs as the dependent variable and the three groups of patients according to their comorbidities as the explanatory variable. Since disease duration may influence both the number of comorbidities and the PROs, additional models adjusting for this variable were explored. After that, the impact of the number of comorbidities on PROs over two years of follow-up was evaluated using mixed models for repeated measures (MMRM) adjusting for disease duration. Finally, we compared the retention rate to the first anti-TNF alpha across the three groups of patients using a Kaplan-Meier curve and a Log-rank test.

Results: 749 patients were included (mean age 48.37 ± 12.2 years, of which 75.3% were men). The association between the number of comorbidities and the PROs is shown in Table 1. We found that patients with 2 or more comorbidities showed an increase (b coefficient) in all PROs compared with patients without comorbidities. The impact of the number of comorbidities on the PROs after two years of follow-up is shown in Figure 1. In general, patients with two or more comorbidities showed higher scores during the two years of follow-up in Global VAS, BASDAI, ASDAS, BASFI and worse levels of the physical component from the SF12.
The impact of the number of comorbidities on the retention rate of the first anti-TNF is shown in Figure 2. We found a higher probability of discontinuation of the first anti-TNF in patients with 2 or more comorbidities compared with the other two groups (38.2% vs. 26.6% vs. 25.4% for 2 or more comorbidities, 0 and 1 comorbidity, respectively), although these differences were not significant (Log-rank test: p-value = 0.180).

Conclusion: In patients with AS, the presence of 2 or more comorbidities was associated with poorer scores on the outcome measures after two years of follow-up, in comparison with patients without comorbidities. Despite the three groups showed a similar use of anti-TNF alpha, a greater tendency of discontinuation of the first anti-TNF was observed in patients with 2 or more comorbidities.

Table 1. Association of the number of comorbidities with PROs.

Figure 1. Impact of the number of comorbidities on PROs over two years of follow-up.

Figure 2. Impact of the number of comorbidities on the adherence to the first TNF-alpha blocker.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/impact-of-the-number-of-comorbidities-on-the-outcome-measures-and-on-the-retention-rate-of-the-first-anti-tnf-in-patients-with-ankylosing-spondylitis-two-year-follow-up-regisponser-as/