Background Axial spondyloarthritis (aSpA) is a chronic inflammatory disease that can lead to irreversible spinal bone damage and loss of spine mobility. However, it is controversial whether the inflammation is coupled with bony change in aSpA. C-reactive protein (CRP) is useful for monitoring disease activity, if it is elevated at baseline.
Objectives To investigate the association of CRP with radiographic spinal progression in aSpA
Methods We reviewed the data of 178 patients with aSpA who visited the rheumatology clinic at our hospital between January 2009 and February 2013. They had at least 2 sets of lateral cervical and lumbar radiographs a minimum of two years apart for assessing the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS). We calculated annual mSASSS change using two different mSASSS. CRP's at the time of taking radiographs were also collected. High CRP was defined as it was ≥10 mg/L. We divided the patients into 4 groups in terms of CRP at baseline and follow-up during treatment: persistently low (LL), persistently high (HH), decreased CRP to low level after treatment (HL), and increased CRP after treatment (LH).
Results Age of the patients was 40.2±12.0 years and female to male was 1:4. Disease duration was 13.3±9.0 years. The patients with HLA-B27 positivity were 91%; those with ankylosing spondylitis were 81%. Radiographs were taken at intervals of 4.5±2.6 years. Seventy four patients were included in LL, 27 in HH, 55 in HL and 5 in LH. The duration of decrease of CRP to low level was 8.9±10.7 months in HL. (Among In the patients of LL, the frequencies of male, initial spinal syndesmophytes, and use of TNF inhibitors decreased compared with other groups.) New spinal syndesmophytes were observed during follow-up in 24% (LL), 44% (HH), 56% (HL) and 40% (LH). Annual mSASSS change was 0.6±1.0 (LL), 1.4±1.5 (HH), 1.5±1.6 (HL), and 0.6±0.8 (LD). The patient with initial high CRP showed significantly more new syndesmophyes and annual mSASSS change than those with initial low CRP. When the patient with high CRP were classified to two groups (48 patients in 10≤ and <30 mg/L, and 37 patients in ≥30 mg/L), however, there was no statistical difference new syndesmophyes and annual mSASSS change between them. Comparing HH and HL, annual mSASSS change did not differ between them. Although it was not statistically significant, new syndesmophytes were more common in HL than in HH.
Conclusions Baseline high CRP (≥10 mg/L) is associated with radiographic spinal progression compared with low CRP. However, the higher CRP was not correlated with the more progressive spinal disease. In addition, there was no difference in spinal bony change between the patients with persistent high CRP and those with a reduction of CRP. Thus, while monitoring the aSpA patients with high baseline CRP, physicians should keep in mind that a decrease in CRP does not guarantee favorable treatment response enough to retard bony progression. Further disease-modifying drugs may be needed to be given for them.
Disclosure of Interest None declared