BACKGROUND:We developed and evaluated a candidate reference measurement procedure (RMP) to standardize testosterone measurements, provide highly accurate and precise value assignments for the CDC Hormone Standardization Program, and ensure accurate and comparable results across testing systems and laboratories.

The emergence and subsequent global outbreak of the novel coronavirus SARS-CoV-2 prompted our laboratory to launch efforts to develop methods for SARS-CoV-2 antigen detection and quantification. We present an isotope dilution mass spectrometry method (IDMS) for rapid and accurate quantification of the primary antigens, spike and nucleocapsid proteins. This IDMS method utilizes liquid chromatography-tandem mass spectrometry (LC-MS/MS) to analyze sample tryptic digests for detection and quantification of selected conserved peptides of SARS-CoV-2 spike and nucleocapsid proteins. The IDMS method has the necessary attributes to be successfully utilized for accurate quantification in SARS-CoV-2 protein-based vaccines and as targets of rapid diagnostic tests. Absolute quantification was achieved by quantifying and averaging 5 peptides for spike protein (3 peptides in the S1 subunit and 2 peptides in the S2 subunit) and 4 peptides for nucleocapsid protein. The overall relative standard deviation of the method was 3.67% for spike protein and 5.11% for nucleocapsid protein. IDMS offers speed (5 hours total analysis time), sensitivity (LOQ; 10 fmol/µL) and precision for quantification of SARS-CoV-2 spike and nucleocapsid proteins.

The inaccuracy of 17-β estradiol (E2) measurements affects its use as a biomarker in patient care and research. Clinical and research communities called for accurate and standardized E2 measurements. Reference Measurement Procedures (RMPs), part of the CDC Hormone Standardization Program (HoSt), are essential in addressing this need and ensuring that methods are accurate and comparable across testing systems, laboratories, and over time. A candidate RMP (cRMP) was developed for the measurement of total E2 in serum using liquid chromatography-tandem mass spectrometry (LC-MS/MS) without derivatization. The cRMP meets suggested performance criteria for accuracy and precision through the use of isotope dilution, calibrator bracketing, and gravimetric measurements. The cRMP demonstrated high agreement with certified reference materials (no significant bias to BCR576, 577, and 578) and established RMPs (slope 1.00, 95% CI 1.00–1.01; intercept 0.02, 95% CI -0.01 to 0.06). The cRMP is highly precise with intra-assay, interassay, and total percent CVs of 2.7%, 1.3%, and 2.4%, respectively. A higher specificity was achieved by measuring E2 without derivatization, compared to methods using derivatization agents. The cRMP can serve as a higher-order standard for establishing measurement traceability and provides an accuracy base against which routine methods can be compared in HoSt.