The Cyfra 21-1 antigen can be measured in concentration through a blood test, which is used to diagnose and monitor the progression of certain cancers. However, it is important to note that Cyfra 21-1 is not a highly specific marker and may be influenced by other factors to produce false-positive or false-negative results. Therefore, when diagnosing with Cyfra 21-1, a patient’s clinical symptoms, imaging studies, and other laboratory findings need to be considered.