Development and evaluation of a candidate reference measurement procedure for detecting 17α-hydroxyprogesterone in dried blood spots using isotope dilution liquid chromatography tandem mass spectrometry

17 alpha-Hydroxyprogesterone (17 alpha-OHP) quantification in dried blood spots (DBS) is essential for newborn screening for congenital adrenal hyperplasia (CAH), which is challenging due to its low physiological concentration. The high false-positive rates of immunoassays necessitate the development of more accurate methods. Liquid chromatography tandem mass spectrometry (LC-MS/MS) offers increased specificity and sensitivity, yet standardized procedures for 17 alpha-OHP measurement are required for clinical application. A candidate reference measurement procedure (cRMP) using isotope dilution LC-MS/MS was developed for 17 alpha-OHP quantification in DBS. By utilizing stable isotope-labeled D8-17 alpha-OHP as an internal standard, the cRMP was optimized, covering sample preparation, calibration, and LC-MS/MS analysis. The method performance was validated across several parameters, including precision, accuracy, specificity, detection limits, and matrix effects. Clinical applicability was further assessed through the establishment of reference intervals for healthy newborns. The developed cRMP exhibited a linear range of 1.00 to 80.00 ng/mL for 17 alpha-OHP, with detection and quantification limits of 0.14 ng/mL and 0.52 ng/mL, respectively. Inter- and intraday precision demonstrated coefficients of variation within 1.27 to 5.69%. The recovery rates and matrix effects were well within acceptable limits, ensuring method reliability. Clinical application showed distinct reference intervals for healthy newborns that were unaffected by sex but influenced by weight and gestational age. This method significantly enhances CAH diagnostic accuracy in newborns, providing a valuable tool for clinical laboratories and improving newborn screening program standardization and traceability.