["Development of fibrosis and subsequent stricture formation in Crohn's disease (CD) increases morbidity and rates of surgery and reduces patients' quality of life. There are currently no biomarkers of intestinal fibrosis that might allow earlier identification and better management of patients at increased risk of stricture formation.", 'MicroRNA profiling of serum from CD patients was used to identify microRNAs associated with stricture formation. Differential expression of miR-19a-3p and miR-19b-3p was validated by quantitative PCR in independent CD cohort of stricturing and nonstricturing patients (n = 46 and n = 62, respectively). Levels of miR-19a-3p and miR-19b-3p were also quantified in baseline serum samples, and expression compared between CD patients who subsequently developed stricture and those who did not (n = 11 and n = 44, respectively).', 'Serum levels of miR-19a-3p and miR-19b-3p in the array were lower in CD patients with a stricturing phenotype than in control CD patients (P = 0.007 and 0.008, respectively). The reduction in miR-19a-3p and 19b-3p was verified in a second cohort (P = 0.002). The association of miR-19-3p with stricturing CD was independent of potential confounding clinical variables, including disease duration, disease activity, site, gender, and age. Serum analyses in patients with 4 years of follow-up support the hypothesis that reduced miR-19a-3p and miR-19b-3p predate stricture development with a trend toward significance (P = 0.077 and P = 0.060, respectively).'] Do low Serum Levels of MicroRNA-19 Are Associated with a Stricturing Crohn 's Disease Phenotype?