We have faced the same problem few weeks ago, when etomidate infusion ( an intravenous 11 beta hydroxylase inhibitor like metyrapone) has to be given to acutely unwell patient in order to medically control hypercotisolism due to ACTH dependent Cushing's disease. Our Siemens cortisol assay showed significant interference compared to mass spectrometry and Roche cortisol assays, see serial cortisol results post 2.5 mg/h etomidate infusion using 3 methods:
Time Our Siemens assay Mass spectrometry Roche cortisol
0h >2070 nmol/L 1450 nmol/L 1588 nmol/L
4h 1735 1183 1312
8h 1546 927 932
12h 1467 845 1009
16h 1140 732 704
20h 1224 726 762
24h 1203 766 756
28h 1236 701 728
32h 1079 620 642
36h 1112 734 727
40h 1035 702 707
Regards
Mohammad
-----Original Message-----
From: Clinical biochemistry discussion list [mailto:[log in to unmask]] On Behalf Of Phillip Monaghan
Sent: 16 November 2016 12:54
To: [log in to unmask]
Subject: Re: Cortisol
Hi John
We published the Siemens data back in 2011:
http://acb.sagepub.com/content/48/5/441.long
The largest difference between Centaur and MS we observed during the study was approx 250 nmol/L, but I have subsequently seen far greater differences between methods, so patient and dose-specific. Structural analogues (in addition to 11DOC) preceeding cortisol in the pathway may have a cumulative effect on cross-reactivity.
Sorry, no data on the Roche, but would advocate mass spectrometry in such cases to mitigate patient harm.
Best wishes,
Phil
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