AB1298 SERUM MMP-3/CRP RATIO IS SIGNIFICANTLY LOWER IN POLYMYALGIA RHEUMATICA THAN IN ELDERLY-ONSET RA
Authors: T. Suzuki, H. Shirai
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> Differentiating between elderly-onset rheumatoid arthritis (EORA) and polymyalgia rheumatica (PMR) is often a problem in daily clinical practice. We have reported that musculoskeletal ultrasound is useful to determine the following differences between polymyalgic-EORA (PM-EORA), which exhibits PMR-like symptoms, and true PMR [1]. The degree of synovial thickening in the shoulder bursa is more severe in PM-EORA [2]. The ratio of extrasynovial to synovial inflammation is higher in true PMR. We also found that the ratio of serum matrix metalloproteinase-3 (MMP-3) to CRP may be useful as a substitute for ultrasoud to distinguish PM-EORA from PMR. <h3>Objectives:</h3> In this study, we investigated whether the serum MMP-3/CRP ratio is useful for differentiating between EORA and PMR, even if it is not limited to PM-EORA. <h3>Methods:</h3> We searched our hospital's medical records from April 2015 to December 2022 and selected patients with EORA and PMR who were 65 years of age or older at the time of onset and whose serum MMP-3 and CRP levels were measured at the same time in pre-treatment testing. The clinical diagnosis made one year after the onset of the disease was adopted as the final diagnosis. EORA was classified as PM-EORA if the shoulder and/or hip showed swelling or severe stiffness, and other cases were classified as NP (non-polymyalgic)-EORA. Mann-Whitney U test and ROC analysis were used for data analysis. MMP-3 was quantified by latex turbidimetric immunoassay (normal range, male: 36.9–121 ng/mL, female: 17.3–59.7 ng/mL). <h3>Results:</h3> We were able to analyze 26 cases of PMR, 36 cases of PM-EORA, and 31 cases of NP-EORA, and the average age at onset was 76.5 years, 77.0 years, and 73.2 years, respectively. The median (IQR) CRP (mg/dL) values were 7.26 (5.44-10.5) for PMR and 1.67 (0.405-4.08) for EORA (including PM-EORA 3.66 (1.33-5.92) and NP-EORA 0.53 (0.24-2.14); There were significant differences between all groups. The median (IQR) MMP-3 (ng/mL) values were 210 (145-274) for PMR and 142 (79.4-267) for EORA, with no significant difference. Significant differences were only between PM-EORA 181 (90.5-381) vs. NP-EORA 119 (65.6-180) and PMR vs. NP-EORA. The median (IQR) MMP-3/CRP ratios (x 10<sup>4</sup>) were 28.3 (17.4-45.6) for PMR and 103 (52.3-234) for EORA (including 67.2 (45.6-169) for PM-EORA and 173 (68.9-455) for NP-EORA), and there were significant differences between all groups (Figure 1A and B). Using ROC analysis, we found that both CRP (cutoff 4.73, AUC 0.842) and MMP/CRP ratio (cutoff 46.2, AUC 0.855) were good in discriminating between PMR and EORA(Figure 2A). However, for PMR versus PM-EORA, the MMP/CRP ratio (cutoff 46.2, AUC 0.811) was better than CRP (cutoff 4.73, AUC 0.751) (Figure 2B). <h3>Conclusion:</h3> The serum MMP-3/CRP ratio is very useful to differentiate between PMR and PM-EORA. Even without distinguishing between PM-EORA and NP-EORA, the serum MMP-3/CRP ratio is lower in PMR than in EORA. The serum MMP-3/CRP ratio can be considered as a biomarker that distinguishes between the pathological condition associated with strong extrasynovial inflammation in PMR and the pathological condition characterized by synovitis in EORA. <h3>REFERENCES:</h3> [1] Suzuki T, et al. Clin Med Insights Arthritis Musculoskelet Disord. 2017 Dec 7;10:1179544117745851. [2] Suzuki T, et al. Biomed Res Int. 2017;2017:4272560. <h3>Acknowledgements:</h3> <b>NIL.</b> <h3>Disclosure of Interests:</h3> Takeshi Suzuki AbbVie, Tanabe, Eli Lilly, Chugai, Taisho, Novartis, Eisai, Bristol-Myers Squibb, Harumi Shirai: None declared.