Assessment of immunoassay calibrators for T, E2, and P4 using UPLC-MS

[madman]

Manufacturer-supplied calibrators for sex steroid immunoassays often have inaccurate concentrations. Only a small percentage of testosterone, estradiol, and progesterone calibrators meet the 20% margin of stated label concentration. The assigned uncertainties of the calibrators don't encompass the discrepancies. Direct steroid immunoassays show method-specific bias compared to mass spectrometry-based methods. Standardization efforts have been made, but deviations persist. Direct steroid immunoassays have limitations in accuracy and validity. LC-MS-based steroid measurement is desired for better accuracy in clinical practice, but cost and expertise pose challenges.

 

[madman]

Table 1: Testosterone immunoassay calibrators.

 

[madman]

Figure 1: Bland-Altman deviance plot (left) and Passing-Bablok regression plot (right) for testosterone calibrators for five different commercial calibrators. The line of identity is shown as a dashed black line.

 

[madman]

Figure 2: Bland-Altman deviance plot (left) and Passing-Bablok regression plot (right) for estradiol calibrators for four different commercial calibrators. The line of identity is shown as a dashed black line.

 

[madman]

Table 2: Estradiol immunoassay calibrators.

 

[madman]

Figure 3: Bland-Altman deviance plot (left) and Passing-Bablok regression plot (right) for progesterone calibrators for four different commercial calibrators. The line of identity is shown as a dashed black line.

 

[madman]

Table 3: Progesterone immunoassay calibrator measurements.

 

[madman]

*Steroid measurements in clinical practice are primarily done using direct, non-extraction immunoassays on automated platforms

*The accuracy of these immunoassays is limited by cross-reactivity, matrix interference, and the accuracy of manufacturer-supplied calibrators

*The accuracy of calibrators for testosterone, estradiol, and progesterone immunoassays was investigated using liquid chromatography-mass spectrometry (LC-MS)

*A significant number of calibrators deviated from the label concentration, with some being outside the 20% margin

*The inaccurate calibration of manufacturer-supplied standards can contribute to the inaccuracy of commercial direct steroid immunoassays

 

[madman]

*Discrepancies persist in steroid measurements despite international standardization efforts

*The Joint Committee for Traceability in Laboratory Medicine (JCTLM) promotes traceability and provides reference materials, measurement procedures, and services for all three measurements

*Manufacturers provide information on reference methods and materials, with only one (Beckman-Coulter E2) explicitly stating it in their product information

*The CDC HoST program supports accuracy in steroid measurements, but currently, only Siemens Centaur testosterone is verified in the program

*Direct steroid immunoassays face difficulty meeting the accuracy-based standards of the CDC HOST program due to inherent method-specific bias