Background/Purpose: To compare the laboratory characteristics of patients who had rheumatic diseases and presented with extremely elevated ESR (≥100 mm/h) and had either disease flare-up or documented infection and to find factors which may help to differentiate patients with disease flare-up and infection.

Methods: In this retrospective analyses, patients -either inpatient or outpatient- with ESR≥100 mm/h between 2015 and 2020 were identified. Patients with a certain diagnosis of inflammatory rheumatic disease and had either disease flare-up or documented infection were included in the analysis. Flare-up was defined as need of newly prescribed immunosuppressive (IS) agents or increment of dose of the already prescribed IS agents and NOT prescription of any kind of antibiotics. Infection was defined as documentation of possible infective agent via culture or imaging finding AND prescription of any kind of antibiotics. Available laboratory data temporarily nearest to ESR≥100 mm/h were recorded. Decision tree by R (package party) was used to construct a clinician-friendly algorithm for the discrimination of disease flare-up and infection by using routine laboratory tests.

Results: Of 311 patients with ESR≥100 mm/h and rheumatic diseases, 225 were included. 111 (49.3%) patients had disease flare-up and 114 (50.7%) patients had infection. In flare-up group, 93 (83.8%) had inflammatory arthritis [57 RA, 31 SPA, 2 JIA, 2 crystal arthritis, 1 adult Still’s disease], 11 (9.9%) had vasculitis [5 large-vessel, 4 small-vessel, 2 PMR] , 7 (6.3%) had connective tissue disorder (CTD) [5 SLE, 1 overlap syndrome and 1 SSc]; however, in infection group 65 (57.0%) had inflammatory arthritis [25 RA, 22 SpA, 6 crystal arthritis, 6 FMF, 4 adult Still’s disease, 2 JIA], 22 (19.3%) had vasculitis [12 small-vessel, 5 large-vessel vasculitis, 2 PMR, 1 relapsing polychondritis, 1 Behcet’s syndrome and 1 PAN] and 27 (23.7%) had CTD [12 SLE, 5 SSc, 3 Sjögren’s syndrome, 3 sarcoidosis, 2 myositis, 1 retroperitoneal fibrosis, 1 granulomatous mastitis]. Thrombocyte, MCV, albumin and total protein were significantly lower in infection group, however; neutrophil, MPV, CRP and ferritin were significantly lower in flare-up group (Table). Lipids, vitamin B12 and complement levels were similar. In decision tree, serum albumin ≤2.78 g/dl was the first branch (89.1% for infection vs. 10.9 for flare-up). If serum albumin >2.78 g/dl, thrombocyte ≤290/mm6 was the second branch (thrombocyte count≤290/mm⁶; 69.2% for infection vs. 30.8% for flare-up // thrombocyte >290/mm6; 32.9% for infection vs. 67.1% for flare-up) (Figure). In multivariable analysis factors were associated with infection over flare-up (reference level): thrombocyte count (per 1/mm⁶ increment) (aOR: 0.997 (0.995-0.999)), albumin (per 1 gr/dl increment) (aOR: 0.37 (0.22-0.63)), CRP (1 mg/dl increment) (aOR: 1.044 (1.011-1.044)).

Conclusion: Extremely elevated ESR is an alarming finding for clinicians who follow-up patients with rheumatic diseases. Flare-up of the underlying rheumatic disease and infections should be kept in mind in patients with such presentation. We have generated a simple and clinician-friendly decision tree in which albumin level and thrombocyte count were key elements.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/extremely-elevated-erythrocyte-sedimentation-rate-revisited-in-rheumatic-diseases-flare-up-or-infection-single-centre-retrospective-analysis/