Background/Purpose: In a preliminary study on 10 patients with active rheumatoid arthritis (RA) we showed for the first time that Power Doppler ultrasonography (PDUS) signal of metacarpophalangeal (MCP) joints has a clear diurnal variation. To test whether PDUS signal of MCP joints in RA patients actually varies according to the time of day, we undertook a larger study involving 50 patients with active RA

Methods: A total of 500 MCP joints from 50 patients with active RA were evaluated at three different times during the same day T1: between 7 and 10 a.m.; T2: 4-6 hours after T1; T3: 4-6 hours after T2. All joints were evaluated for both presence/absence of PDUS signal and according to a semiquantitative score (from 0 to 3). The results at T1, T2 and T3 were compared for each joint. The day of examination, factors that could potentially influence PDUS signal were avoided or controlled (smoke, alcohol, corticosteroids, NSAIDs, vasoactive drugs intake, room temperature, hand position). Within-patient PDUS score variation was quantified as the sum of the differences between PDUS scores in each joint at the three different examinations for each patient. Semiquantitive PDUS scores were compared with Friedman’s test. Categorical data (PDUS presence/absence) were compared with Cochran’s Q test

Results: Globally, 46 out of 50 patients (92%; CI : 84.48% to 99.52%) displayed some circadian variation of PDUS signal. There was a significant variation in the number of PDUS-positive MCP joints during the day (p<0.05), with more PDUS positive MCP joints at T0 (156) vs. T1 (144) and T2 (129) (p<0.05). Fifteen patients (30%; 95CI 17.3% to 42.7%) had at least one joint in which PDUS signal appeared or disappeared at different. Semiquantitative PDUS scores were significantly higher at T1 (p<0.05 vs. T2 and T3) with a subsequent reduction at T2 (p<0,05 vs. T1 and T3) and further reduction at T3 (p<0,05 vs. T1 and T2). This pattern of variation was not univocal and single patients and even single joints in the same patient could show higher scores at T2 or, more rarely, at T3.  Median within-patient PDUS score variation was 4 (range 0 to 34). Patients with higher than the median PDUS variation had higher DAS28 (p<0.05), but no higher CRP vs. those with lower variation.  Within-patient variation was moderately correlated with DAS28 (r=0.4, p=0.01) but not with CRP

Conclusion: PDUS signal varies significantly through the day, being higher in the morning and progressively lowering in early afternoon and evening. PDUS signal variation involved about 90% of patients, independent of disease activity. Patients with higher disease activity displayed greater variation of PDUS signal

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/diurnal-variation-of-power-doppler-in-metacarpophalangeal-joints-of-patients-with-rheumatoid-arthritis/