We conclude that for the detection of iron depletion, i.e., IDA or concomitant ACD and IDA, in anemic RA patients, the measurement of sTfR is superior to standard parameters of iron deficiency only in patients with high inflammatory activity, whereas in patients with low inflammation, the determination of sTfR does not exceed the diagnostic performance of standard parameters with even higher sensitivity of the combined use of standard markers of iron status. The gene discussed is TFRC; the disease is nutritional disorder.