Objective: This project aims to evaluate the effect of two isotopically labelled internal standards on the quantification of 17OHP by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and gas chromatography-tandem mass spectrometry (GC-MS/MS) as an orthogonal technique.
Methods: Three LC-MS/MS and one GC-MS/MS laboratories, spanning four countries worldwide, who routinely measure serum17OHP, compared two internal standards as part of their patient runs. The only change to the respective laboratory standard operating procedure was the substitution of their internal standard (if different to in-house method) with: 1) IsoSciences carbon-13 labelled 17OHP-[2,3,4-13C3]; and 2) IsoSciences deuterated 17OHP-[2,2,4,6,6,21,21,21-D8]. Statistical interpretation of the data is based on the slope from the Passing Bablok regression, difference from the Bland Altman plots and the Student two tailed paired t-test, with confidence intervals (CI) of 95% and level of significance P<0.05 applied.
Results: The three LC-MS/MS and one GC-MS/MS laboratories successfully evaluated the two internal standards against altogether 232 patient samples. Analysis of the 13C- and D-labelled internal standard results from the individual laboratories, along with the combined all laboratory data, demonstrated agreement: the Passing-Bablok regression slope to include one in the CI; and Bland Altman difference to include zero in the CI. The all laboratory data t-test demonstrated a p>0.05
Conclusions: Overall, the comparison between the results of 13C- and D-labelled internal standards for 17OHP showed not influence by the internal standard used.
19 - 21 Sep 2019
European Society for Paediatric Endocrinology