Ana Maria Herrero-Beites, Fernando Perez-Ruiz
Affiliation(s):
Rehabilitation division, Gorliz hospital and rheumatology division, Cruces University Hospital
Background: persistence of flares in patients with gout after proper treat-to target treatment approach raise the question whether coexistence of a disease with similar clinical characteristics could be at work, namely “pseudogout”.
Aim: to ascertain the prevalence of CPPA at diagnosis and during follow-up of patients with gout.
Method: data from an inception cohort of patients with gout prospectively followed-up from Jan 1994 to Dec 2023 (30 year). Gout-case was defined as crystal-proved tophus or arthritis, or presence of tophus plus double contour with ultrasonography. CPPA was defined as the presence of intra-leukocyte CPP crystals in synovial fluid (SF), and neat chondrocalcinosis in the same or a different joint. Age, gender, flares, joint distribution, previous treatment, prescribed treatment, comorbidities (hypertension/hyperlipidemia/diabetes), use of diuretics, renal function, previous vascular disease were available for analysis.
Results: 1,544 patients with gout, with an average of 4-year follow-up (1 month to 32 year) were available for analysis. CPPA was observed in 127 cases (8.2%): 37/1544 patients or 37/1224 synovial fluid samples (2.4% and 3.0% respectively) showed CPP and urate crystals in the same synovial sample (cousins-not-brothers image), and 90/1544 (5.8%) patients showed CPP crystals apart from the diagnosis of gout: 3 had a previous diagnosis, 60/90 (66.6%) a diagnosis after the first 5-year period of follow-up.
CPPA-gout cases referred more flares per year (3.59 vs 3.82, p=0.087) but no more polyarticular involvement at baseline (81/1007, 8.0% vs. 46/537, 8.6%, p=0.911), compared to non-CPPA.
In bivariate analysis, CPPA-gout cases were older at baseline (72±11 vs 61±13 years). Women 20/148, 3.5% vs. 107/1396, 7.7%), patients using diuretics (72/546, 13.7% vs. 55/1018, 5.4%), patients with hypertension (102/884 6.6% vs. 25/660, 1.6%), previous vascular event (64/514, 12.5% vs. 63/1030, 6.1%) were more frequently affected. Ethanol intake over 15 g/d was apparently protective (26/479, 5.4% vs. 101/1065, 9.5%). Other variables were not associated, and multivariate analysis showed that only age and diuretics were independently associated with CPPA.
Interestingly, an analysis of the prevalence in the three decades available showed an increase in CPPA diagnosis: 18/454 (4%), 50/543 (9.2%), and 59/547 (10.8%), and also for finding CPP and urate crystals in the same sample: 0/436, 13/420 (3.1%), and 24/368 (6.5%), respectively for first, second, and third decade.
Conclusions: 1) CPPA is not infrequent in patients with gout; 2) It is associated to aging and diuretic use; 3) Most patients with CPPA-gout flared after 5-year proper control, inducing a suspicion of an associated disease; 4) Joint aspiration and careful evaluation of SF is recommended in such patients.