A drawback to using the TS is that it depends on performing both the SI and TIBC. The unsaturated iron-binding capacity (UIBC) may be a lower-cost alternative.
The optimal TS criterion for detecting HH is controversial. A TS of >60% for males and >50% for females is highly accurate in detecting abnormal iron metabolism in persons with HH. Other studies suggest using lower TS levels, e.g., 45%, as a criterion, indicating further testing is warranted. Current guidelines from the American College of Physicians include a TS cutoff level of >55% for identifying iron overload.14 A TS cutoff level of >45% is recommended by the American Association for the Study of Liver Disease.15
Patients with initially increased TS should be followed by performing a second TS from a fasting morning specimen. The patient should also be advised not to take vitamins supplemented with iron or oral contraceptives for several days before the repeated test. TS levels may be affected by diurnal variation, dietary factors, and co-existing disease states such as inflammation and hepatitis. Patients with HH may have falsely normal TS if chronic blood loss or inflammatory disease is present.
