In a patient with suggestive symptoms, physical findings, or family history, a combination of transferrin saturation (TS) and ferritin should be obtained rather than relying on a
single test. If either TS is >45% or ferritin is above the upper limit of normal) then HFE
mutation analysis should be performed. Although a cutoff TS value of 45% is often chosen for its high sensitivity for detecting C282Y homozygotes, it has a lower specificity and positive predictive value compared to higher cutoff values. Using a cutoff TS of 45% will also identify persons with minor secondary iron overload. Serum ferritin has less biological variability than TS, but it has a significant false positive rate because of elevations related to inflammation. Serum ferritin levels may range anywhere from 150-1000 (typically asymptomatic) up to 500-6000+ (usually symptomatic). Testing should also be sent on adult 1st degree relatives of individuals with confirmed hereditary hemochromatosis.
References: Diagnosis and management of hemochromatosis