Measurement of serum 17-hydroxyprogesterone using isotope dilution liquid chromatography-tandem mass spectrometry candidate reference method and evaluation of the performance for three routine methods

OBJECTIVES Accurate measurements of serum 17-hydroxyprogesterone (17OHP) are essential for diagnosis and treatment monitoring for congenital adrenal hyperplasia patients. The performance of serum 17OHP routine methods remains highly variable that calls for a candidate reference measurement procedure (cRMP) to improve the standardization of serum 17OHP measurements. METHODS Serum samples spiked with internal standards were extracted with a combination of solid-phase extraction and liquid-liquid extraction. The 17OHP was quantified by the isotope dilution coupled with liquid chromatography/tandem mass spectrometry (ID-LC/MS/MS) with electrospray ionization in positive ion mode. Nine structural analogs of 17OHP were evaluated for interferences. The precision and analytical recovery were assessed. Twenty native and 40 spiked serum for performance evaluation were measured by the cRMP and two clinical LC/MS routine methods. RESULTS No apparent interferences were found with the 17OHP measurement. The within-run, between-run, and total precision for our method were 0.4-0.8%, 0.6-2.0%, and 1.0-2.1% for four pooled serum (2.46-102.72 nmol/L), respectively. The recoveries of added 17OHP were 100.0-100.2%. For the performance of two LC/MS routine methods, they showed relative deviation ranges of -22.1 to 1.1% and -6.7 to 12.8%, respectively. CONCLUSIONS We developed and validated a reliable serum 17OHP method using ID-LC/MS/MS. The desirable accuracy and precision of this method enable it to serve as a promising cRMP to improve the standardization for serum 17OHP routine measurements.