LAUSR

Background As Japan is a super-aged society, we have many chances to care for elderly patients in our hospital. Elderly-onset rheumatoid arthritis (RA) (onset age >60 years) may present similar symptoms to those of polymyalgia rheumatica (PMR). We consider that differential diagnosis of RA and PMR is more difficult in patients over 75 than those under 74 in clinical practice. Anti-cyclic citrullinated peptide antibody (ACPA) was reported to be a helpful tool in the differential diagnosis of EORA from PMR. However, when elderly patients with negative ACPA complained of bilateral shoulder and/or girdle pain, it was difficult to differentiate PMR from RA. Objectives The study aimed to explore clinical features of RA and PMR at onset age 75 years. For the present investigation, we used a novel diagnostic tool to distinguish ACPA-negative elderly RA patients from PMR patients at initial presentation. Methods From April 2011 to December 2016, 21 RA patients and 24 PMR patients in our hospital, whose onset age was over 75 years, were recruited for this study. PMR patients did not have any evidence of giant cell arteritis. The diagnosis of RA was made based on 2010 ACR/EULAR RA classification criteria. The diagnosis of PMR was made based on 2012 EULAR/ACR classification criteria or Bird's criteria. Data were obtained from medical records under informed consent. Statistical analysis was performed using the Mann-Whitney U-test to compare median values and Fisher's exact test to compare frequencies (IBM SPSS version 24). P<0.05 indicated statistical significance. Results RA patients (6 men and 15 women) consisted of fifteen ACPA+ (11 RF+, 4 RF–), six ACPA– (1 RF+, 5 RF–). PMR patients consisted of 12 men and 12 women. All of them were ACPA–/RF– and did not meet 2010 RA criteria. Twenty patients met 2012 PMR classification criteria, and 4 patients without bilateral shoulder pain met Bird's criteria. Clinical features and statistical results are shown in the Table. Sixty-seven percent of RA patients and 13% of PMR patients had left-right differences in joint pain. Scoring was performed based on clinical findings. Tenderness and/or swelling joint counts among wrists, fingers, ankles, and knees = each 1 point, left-right difference =1 point, no bilateral shoulder pain =1 point, no girdle pain =1 point, no fever =1 point; the maximum score was 8. The mean score in RA patients was 4.8 (SD =1.44), whereas that in PMR patients was significantly lower at 1.5 (0.98) (P<0.001). Receiver operating characteristic (ROC) curve analysis was used to determine the most suitable cut-off level to find RA. A score over 3 was 100% sensitivity and 87.5% specificity. All 6 ACPA-negative RA patients showed a score over 4. Conclusions Pease et al studied RA at onset 60 years and over and PMR, and reported that arthritis of wrists and fingers was suggestive of RA1. However, in our study, small joint swelling was rare in RA patients 75 years and older. The scoring system we made might be useful for the differential diagnosis of ACPA-negative RA and PMR in elderly patients 75 years and older. References Pease CT, et al. Diagnosing late onset rheumatoid arthritis, polymyalgia rheumatica, and temporal arteritis in patients presenting with polymyalgic symptoms. A prospective longterm evaluation. J Rheumatol 32: 1043–1046, 2005. Disclosure of Interest None declared