Interferences in testosterone assays - can LCMS be affected?? (#223)
Aim: To report possible interference in testosterone on immunoassay and LCMS (Liquid Chromatography/Mass Spectrometry)
Background: Many laboratories use testosterone immunoassays routinely with more laborious and time consuming LC/MS assays reserved for confirmation of abnormal results and to exclude interferences.
Method: A 30 year old woman with acne, referred for endocrine review had elevated testosterone (8.7nmol/L -Range < 2.0 nmol/L) on routine testosterone immunoassay. Her only medication was ethinyloestradiol /dienogest
(Valette ). On examination there was mild acne but no virilisation. Abdominal and pelvic examinations were normal with unremarkable pelvic ultrasound and abdominal CT. The laboratory advised immunoassay testosterone was confirmed and that the sample had also been analysed by LC/MS at an independent laboratory with significantly elevated testosterone re-confirmed (LC/MS testosterone = 9.9 nmol/L). Additional tests including progesterone, 17 OH Progesterone, DHEAS, plasma metadrenalines were normal. SHBG was elevated at 275 nmol/L (Reference limits 30-90 nmol/L). On discussion with the Pathologist, a trial of cessation of Valette was suggested if acceptable with patient to exclude interference in both LC/MS and routine testosterone immunoassay.
Results: 9 days after cessation of therapy testosterone was 1.2 nmol/l with SHBG 194 nmol/L. Follow up blood after 1 month confirmed testosterone 1.6 nmol/L and with further decrease in SHBG to 47 nmol/L consistent with discontinuation of OCP. Review of the structure of dienogest confirmed a similar structure to testosterone with a carbon-nitrogen triple bond.
Conclusion: This case raises the possibility of interference with both immunoassay and LC/MS testosterone methods. Clinical review, careful assessment and discussion with laboratory experts may help clarify abnormal testosterone results. The similar structure of dienogest to testosterone suggests that metabolites created in vivo may be interfering with both immunoassay and LC/MS in this patient however further confirmatory studies would be appropriate.
- Annals Of Clinical Biochemistry 2007;44 (pt.1):5-15 AUTHOR: Kane J, Middle J, Cawood M. TITLE: Measurement of serum testosterone in women; what should we do? Tietz textbook of clinical biochemistry and molecular genetics, 4th edition. J Clin Endocrinol Metab. 2007 Feb;92(2):405-13. Epub 2006 Nov 7. Position statement: Utility, limitations, and pitfalls in measuring testosterone: an Endocrine Society position statement. Rosner W, Auchus RJ, Azziz R, Sluss PM, Raff H.