The present invention relates to compositions and methods use in designing immunoassay controls. In various aspects, the invention provides synthetic peptides comprising the sequence CPRRPYIL or an analog thereof; ELAGLGFAELQC or an analog thereof; and CDWRKNIDAL or an analog thereof; specific binding reagents that bind to a CPRRPYIL, ELAGLGFAELQC or CDWRKNIDAL peptide; methods of producing such reagents; and assays utilizing such reagents to provide assay controls signals that are unrelated to the measurement of the analyte or analytes of interest in that no reagents used in the analyte assay(s) contribute to the control signal.