Can RDW be used as a screening test for subclinical inflammation in children with FMF? Is RDW related to MEFV gene mutations?

Objective Subclinical inflammation, an insidious feature of familial Mediterranean fever (FMF), can lead to life-threatening amyloidosis. We aimed to investigate acute phase reactants and complete blood count parameters to identify a useful marker for subclinical inflammation in children with FMF. A secondary aim was to identify an association between subclinical inflammation and specific Mediterranean fever (MEFV) gene mutations. Methods This study included 420 pediatric patients with FMF. Laboratory parameters of patients during the attack-free period and MEFV gene mutation analyses were recorded. Results Of the 420 patients, 88 (21%) had subclinical inflammation. Of those with subclinical inflammation, 48 (55%) had mutations in exon 10, 36 (41%) had M694V mutation, and 10 (11%) had M694V homozygous mutation. Red cell distribution width (RDW) value was higher in exon 10, M694V, and M694V homozygous mutations compared to other mutations. RDW was positively correlated with serum amyloid A (SAA) ( r = 0.390, p = 0.0001). Analysis of a receiver-operating characteristic curve of RDW revealed that its optimal cut-off value for subclinical inflammation was 12.69%, its sensitivity was 64.10%, and its specificity was 50.90%. The area under the curve was 0.616 ( p = 0.004, 95% confidence interval = 0.538–0.695). Conclusion We suggest that RDW can be used as a screening test as a marker of subclinical inflammation. A high RDW value should alert the clinician about subclinical inflammation in FMF children’s patients with M694V (heterozygous, homozygous, compound heterozygous) mutation. Key Points • Subclinical inflammation in FMF patients can lead to amyloidosis. • RDW can be a predictor of subclinical inflammation. • RDW can be used as a screening test for subclinical inflammation in FMF patients with M694V mutation.