Furthermore, in patients with unexplained IDA unresponsive to oral iron treatment who have a very low malignancy risk (e.g., children and young adults) and no signs of inflammatory or ulcerative disease, application of the TSAT/hepcidin ratio may prevent unnecessary invasive gastrointestinal endoscopy if patients with a ratio suspect for having IRIDA are referred for TMPRRS6 sequencing before performing an endoscopic evaluation. The gene discussed is HAMP; the disease is ulcer disease.