Cytokines can be thought of as the hormones of the immune system.  They are small proteins which play an integral role in cell signaling with key roles in host immune responses to infection, inflammation, trauma, sepsis, cancer, and reproduction.  Cytokine testing is primarily used for research and to support attempts to understand the pathogenesis of immune, infectious, allergic, or inflammatory disorders.  Clinical testing for cytokines, for the most part, has no established diagnostic utility for any particular disease or illness.  It is, however, gaining greater clinical utility for monitoring cytokine and immunomodulating therapies, safety monitoring of clinical trials and cytokine storm syndrome.  There are currently no FDA-cleared invitro diagnostic tests approved for cytokine testing, requiring stringent validation by reference laboratories in order to offer cytokine testing in the clinical setting.  Research use only or laboratory developed tests should therefore be thoroughly validated following Clinical and Laboratory Standards Institute (CSLI) guidelines for accuracy, precision, linearity, detection capability, interfering substances, analyte stability and establishing specimen type specific reference intervals.