Measurement of dehydroepiandrosterone sulphate (DHEAS): a comparison of Isotope-Dilution Liquid Chromatography Tandem Mass Spectrometry (ID-LC-MS/MS) and seven currently available immunoassays.

BACKGROUND: Dehydroepiandrosterone sulphate (DHEAS) is an important marker of the adrenal gland. Its measurement is required in several adrenal diseases, such as adrenal tumours, adrenal insufficiency and congenital adrenal hyperplasia. Most clinical laboratories measure DHEAS using commercially available immunoassays. The aim of the present study was to investigate the accuracy of currently available DHEAS methods. METHODS: Seven commercially available DHEAS assays were compared to Isotope-Dilution Liquid Chromatography Tandem Mass Spectrometry (ID-LC-MS/MS) by measuring 75 serum samples (concentration range 0.06-20.6 µmol/L measured by ID-LC-MS/MS) with each method. Moreover, recovery and linearity experiments were performed. Data from our present study were compared to DHEAS data of the Dutch, German and British External Quality Assessment Schemes (EQAS's). RESULTS: Three methods agreed well with ID-LC-MS/MS (R between 0.93 and 0.99 and slopes ranging from 0.92 to 1.07) and showed good recoveries. Four methods showed standardization problems (slopes were 0.84, 1.14, 1.20 and 1.28). Linearity was good in all methods. Intra-assay coefficient of variation was 4.1% using ID-LC-MS/MS and below 5.5% in immunometric methods; one assay had an unacceptably high intra-assay coefficient of variation of 18%. Our data are in agreement with data obtained in three EQAS's. CONCLUSION: Some of the commercially available DHEAS methods show standardization problems and/or a high imprecision. These problems may potentially have clinically adverse consequences. We advise the manufacturers to improve their assays and laboratory specialists to scrutinize the DHEAS method they employ.