David Taylor | Viapath
Clinical Scientist/ Operations Lead
Department of Clinical Biochemistry | King's College Hospital | London | SE5 9RS
020 3299 4131 (direct)
Fax 020 3299 3140
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www.viapath.co.uk

 

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Dear Collective

Our endocrinologists have recently attended the BES conference and have questioned the accuracy of Cortisol measurements (Roche Gen 2) for patients taking Metyrapone. Although Metyrapone does not cross react in that immunoassay, patients taking Metyrapone are likely to have raised 11 Deoxy cortisol which does cross react and can lead to falsely raised Cortisol results. I did a lit search and found that the interference is small (4.6%) see https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4112981/table/T1/ but the posters at BES suggest much greater cross reactivity. I am sure Viapath use Advia Centaur, but even then the cross reactivity is only 23%

Has anyone looked into this with Roche Gen 2 Cortisol kits.

BW John

 

 

 

P79

Immunoassay cortisol day curve dangerously overestimates cortisol reserve in a metyrapone treated patient
Christine H M Leong1, David R Taylor2, Jackie Gilbert1 &
Benjamin C Whitelaw1

1Department of Endocrinology, King’s College Hospital NHS Foundation Trust, London, UK; 2Department of Clinical Biochemistry, Viapath Analytics, King’s College Hospital NHS Foundation Trust, London, UK.

Background
Metyrapone is commonly used in medical management of Cushing’s syndrome. It inhibits 11-b hydroxylase, which catalyses the conversion of 11-deoxycortisol to cortisol. The adequacy of metyrapone blockade can be assessed either clinically or biochemically using a target mean serum cortisol 150–300 nmol/l. Cortisol is normally measured by immunoassay.
Case report
A 21-year-old female presented with clinical and biochemical features of cortisol excess. 0900 h cortisol and basal ACTH were elevated at 1,168 nmol/l and 49 ng/l respectively. 24-h urinary free cortisol was markedly raised at 2,014 nmol/24 h (NR! 200 nmol/24 h). There was failure to suppress cortisol following 1 and 8 mg overnight dexamethasone suppression tests (cortisol 623 and 94 nmol/L). MRI revealed a 7 mm left-sided pituitary adenoma and baseline cortisol day curve demonstrated a mean cortisol of 751 nmol/l. Due to the severity of Cushing’s preoperative medical blockade was initiated. Mean cortisol values on subsequent monthly Metyrapone Day curves were 565, 541 and 867 nmol/l. As cortisol values were markedly above target, metyrapone was increased from 500 mg TDS to 750 mg TDS.
She reported feeling increasingly tired and light-headed and repeat metyrapone day curve demonstrated an elevated mean cortisol of 678 nmol/l. Liquid chromatography- tandem mass spectrometry assay (LC-MS/MS) was then utilised to re-assess her cortisol samples and revealed mean LC-MS/MS cortisol of 87 nmol/l; overestimating cortisol by 591 nmol/l. LC-MS/MS analyses of the previous three samples revealed low mean cortisols of 132, 96 and 104 nmol/L respectively. Conclusion
Metyrapone causes elevated circulating levels of 11-deoxycortisol which can cross-react in immunoassays. This can result in serum cortisol appearing normal or increased despite genuine hypocortisolaemia. The clinical consequences of this include potentially fatal hypocortisolaemic crisis. This case demonstrates that using LC-MS/MS is essential for accurate assessment of medical blockade with metyrapone. Centres that conduct metyrapone day curves using immunoassay may be exposed to dangerous cortisol overestimation.
DOI: 10.1530/endoabs.44.P79 

P8

Full characterisation of adrenal steroidogenesis by liquid- chromatography–mass spectrometry (LC–MS/MS) in metyrapone and/or ketoconazole-treated pituitary/adrenal Cushing’s
David R Taylor1, Christine H M Leong2, Aagna E Bhatt1, Lea Ghataore1, Simon Aylwin2, Ben Whitelaw2 & Royce P Vincent1
1Department of Clinical Biochemistry, Viapath Analytics, King’s College Hospital, London, UK; 2Department of Endocrinology, King’s College Hospital, London, UK.

Introduction
Pituitary and adrenal Cushing’s may be managed by pharmacological-inhibition of adrenal steroidogenesis, using metyrapone and/or ketoconazole. Assessment of biochemical control is challenging owing to cross-reactivity in immunoassays (e.g. cortisol and 11-deoxycortisol) leading to over/under-treatment. Off-target effects can also result, e.g. hyperandrogenism/mineralocorticoid hypertension (increased 11-deoxycorticosterone/DOC). LC-MS/MS analysis is free from cross-reactivity and allows quantification of multiple steroids.
Aim
Evaluate the utility of an LC-MS/MS method quantifying 13 steroids in medically-managed Cushing’s.
Methods
Eighty-one day curves (24 cases) were evaluated by LC-MS/MS and Centaur XP cortisol immunoassay. Thirteen had pituitary-disease (metyraponeGketocona- zole treatment) and 11 had adrenal-disease (metyrapone-only).
Results
In the metyrapone-only groups, pituitary-disease received a larger dose than adrenal-disease (1500 vs 750 mg/d, PZ0.0004). Steroid concentrations were similar between pituitary/adrenal groups, except 11-deoxycortisol (80.6 vs 41.1 nmol/l, PZ0.04), androstenedione (16.4 vs 6.6 nmol/l, PZ0.001) and DHEAS (4.7 vs 0.6 mmol/l, P%0.0001). In pituitary-disease, metyrapone dose positively correlated with 11-deoxycortisol (rsZ0.53, PZ0.01). In adrenal- disease, dose positively correlated with 11-deoxycortisol (rsZ0.77), DOC (rsZ0.59), 17-hydroxyprogesterone (rsZ0.56) and androstenedione (rsZ0.42, all P%0.005) and negatively with cortisol (rsZK0.45, PZ0.02). Cortisol method agreement differed: pituitary-disease LC-MS/MSZ0.28 immunoassay C101.1 nmol/l and adrenal-disease LC-MS/MSZ0.82 immunoassay G 8.7 nmol/l. Pituitary-disease treated with metyrapone and ketoconazole had higher 11-deoxycortisol (PZ0.0003), 17-hydroxyprogesterone (PZ0.0006) and DOC (PZ!0.0001) than those treated with metyrapone-only. LC-MS/MS cortisol was lower in the dual therapy group (128 vs 205 nmol/l, PZ0.01) but relatively higher by immunoassay (350 vs 232 nmol/l, NS). Cortisol method agreement in the metyraponeGketoconazole group: LC-MS/MSZ0.62 immuno- assayG32.1 nmol/l. Seven/fourteen females demonstrated biochemical hyperan- drogenism [increased testosterone/androstenedione (nZ5), androstenedione-only (nZ2)]. Across all day curves, those with highest DOC had relatively lower potassium concentration.

Conclusions
Marked differences in steroidogenesis were observed in pituitary vs adrenal Cushing’s. Unpredictable cross-reactivity in cortisol immunoassays mandates LC-MS/MS use in monitoring. Additionally, LC-MS/MS offers quantification of off-target steroidogenesis effects which may be clinically relevant.

 

 

 

 

 

 

 

Dr John O’Connor

Consultant Clinical Scientist

Lead Scientist RDE

 

Website: www.exeterlaboratory.com

 

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