The Value of Serum Amyloid A Levels in Familial Mediterranean Fever to Identify Occult Inflammation During Asymptomatic Periods

Objective The aim of this observational study was to evaluate whether there was any correlation between the acute phase reactants in children with familial Mediterranean fever (FMF) during attack and attack-free periods. Methods The study was conducted between June 2016 and January 2018. Clinical features and laboratory parameters of children with FMF during attack and attack-free periods were recorded longitudinally. Results The cohort consisted of 168 children with FMF (84 boys, 84 girls). Median values of acute phase reactants during FMF attacks were 433.5 mg/L (34.0–1780.0 mg/L) for serum amyloid A (SAA), 56.7 mg/L (7.6–379.0 mg/L) for C-reactive protein (CRP), and 37.5 mm/h (5–100 mm/h) for erythrocyte sedimentation rate (ESR). Median values for the same tests in attack-free periods were 3.2 mg/L (0.1–25.0 mg/L), 1.7 mg/L (0.1–12.7 mg/L), and 8 mm/h (1–30 mm/h), respectively. Correlation analyses showed that SAA and CRP were highly correlated in FMF attack (r = 0.67, p < 0.01), but no correlation was found between SAA and ESR levels. C-reactive protein was elevated in 13.6%, ESR in 20.8%, and SAA in 28.5% of the patients during attack-free period. Age at onset, sex of the patients, and characteristics of attacks were found to be not associated with elevated SAA in attack-free period. On the other hand, having homozygous exon 10 mutation and having elevated CRP were found to be associated with high SAA in attack-free period. Conclusions C-reactive protein and SAA correlate well with FMF attacks. Therefore, checking for SAA during a FMF attack is not required. However, SAA seems to be the most sensitive method for demonstrating subclinical inflammation in attack-free period. Thus, checking SAA levels might be a valuable tool in selected FMF patients.