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Thermo Scientific B · R · A · H · M · S CT-proAVP LIA for use in endocrinology. February 2011. Vasopressin & CT-proAVP - FAQs. What is Vasopressin (CT-proAVP) and where is it produced? What is the physiological role of Vasopressin? Why not simply measure Vasopressin?

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Thermo scientific b r a h m s ct proavp lia for use in endocrinology l.jpg

Thermo Scientific B·R·A·H·M·S CT-proAVP LIA for use in endocrinology

February 2011


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Vasopressin & CT-proAVP - FAQs

  • What is Vasopressin (CT-proAVP) and where is it produced?

  • What is the physiological role of Vasopressin?

  • Why not simply measure Vasopressin?

  • Is CT-proAVP produced together with Vasopressin?

  • Do both analytes show the same kinetics?

  • Which CT-proAVP levels should be expected in normals?

  • Thermo Scientific B·R·A·H·M·S CT-proAVP LIA in the Differential Diagnosis of Diabetes insipidus

  • What about the performance of the Thermo Scientific B·R·A·H·M·S CT-proAVP LIA Assay?


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What is Vasopressin

and

where is it produced?


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Structure of Vasopressin

O

NH2

O

NH2

-C

  • Arginine-Vasopressin (AVP)

  • synonym: Vasopressin or antidiuretic hormone (ADH)

  • peptide hormone

  • 9 amino acids

  • Disulfide bridge between two cysteine amino acids

  • C-terminal amidation

NH2-


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Synthesis of Vasopressin

  • Synthesis as a precursor hormone (pre-pro-vasopressin) in the hypothalamus

  • Cleavage and transport in granules

  • down the axons

  • Storage in granules in the posterior pituitary

  • Release into nearby capillaries upon

  • appropriate stimulation

Figures adapted from: Golenhofen, Basislehrbuch Physiologie, Urban & Fischer; and Morgenthaler NG et al.: Clin Chem 2006

Information: Russel IC and Glover PJ: Critical Care and Resuscitation 2002; Ranger GS: IJCP 2002; Oghlakian G and Klapholz M: Cardiology in Review 2009


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What is the physiological role of Vasopressin?


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Vasopressin - physiological role

Main role:

Regulation of water balance

- Increased plasma osmolality

- Decreased arterial circulating volume

AVP:

acts via V2-receptors in the kidney

-> water retention

AVP:

Synthesis in the Hypothalamus

Figure adapted from: Knoers NV N Engl J Med. 2005 May 5;352(18):1847-50


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Vasopressin (AVP) effects

  • Effects of AVP dependent on concentration :

  • maximal antidiuretic effect: below 15 pg/ml

  • vasoconstrictor effect at higher concentrations

  • very little effect on blood pressure at physiological levels!

Singh Ranger G, Int J Clin Pract 2002; 56(10):777-782


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Vasopressin in stress situation

Myocardialinfarction

STRESS

AVP

ACTH

Cortisol


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Why not simply measure Vasopressin?


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Vasopressin

Quantification of Vasopressin is difficult


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Vasopressin

Receptor

Vasopressin

Quantification of Vasopressin is difficult


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Vasopressin

Receptor

Vasopressin

Vasopressin

Platelets

Quantification of Vasopressin is difficult


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Protease

Vasopressin

Vasopressin

Receptor

Vasopressin

Vasopressin

Platelets

Quantification of Vasopressin is difficult


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Protease

Vasopressin

Vasopressin

Receptor

Vasopressin

Vasopressin

Platelets

Quantification of Vasopressin is difficult

Further problem: very unstable ex vivo (even frozen)


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Protease

Vasopressin

Vasopressin

Receptor

Vasopressin

Vasopressin

Platelets

Quantification of Vasopressin is difficult

Further problem: very unstable ex vivo (even frozen)

Only specialized labs measure AVP (time to results several days)

Not a single FDA approved AVP assay on the market

LIMITED CLINICAL USE


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Prohormone processing and assay

Signal

Vasopressin

CT-proAVP

Neurophysin II

Morgenthaler NG et al., Clin Chem. 2006


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Signal Peptidase

Prohormone processing and assay

Signal

Vasopressin

CT-proAVP

Neurophysin II

Vasopressin

CT-proAVP

Neurophysin II

Morgenthaler NG et al., Clin Chem. 2006


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Signal Peptidase

ProhormoneConvertase

Vasopressin

Prohormone processing and assay

Signal

Vasopressin

CT-proAVP

Neurophysin II

Vasopressin

CT-proAVP

Neurophysin II

Neurophysin II

CT-proAVP

Morgenthaler NG et al., Clin Chem. 2006


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Signal Peptidase

ProhormoneConvertase

Vasopressin

Prohormone processing and assay

Signal

Vasopressin

CT-proAVP

Neurophysin II

Vasopressin

CT-proAVP

Neurophysin II

Neurophysin II

CT-proAVP

Morgenthaler NG et al., Clin Chem. 2006


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Signal Peptidase

ProhormoneConvertase

Vasopressin

Prohormone processing and assay

Signal

Vasopressin

CT-proAVP

Neurophysin II

Vasopressin

CT-proAVP

Neurophysin II

Neurophysin II

CT-proAVP very

stable ex vivo

CT-proAVP

Morgenthaler NG et al., Clin Chem. 2006


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Signal Peptidase

ProhormoneConvertase

Vasopressin

Prohormone processing and assay

Signal

Vasopressin

CT-proAVP

Neurophysin II

Vasopressin

CT-proAVP

Neurophysin II

Neurophysin II

CT-proAVP very

stable ex vivo

CT-proAVP

Morgenthaler NG et al., Clin Chem. 2006


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Is CT-proAVP produced together with Vasopressin?

Do both analytes show the same kinetics in vivo?


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Correlation of Vasopressin and CT-proAVP

LIA Assay

r = 0.78

Jochberger S et al., Schock 2009 31: 132-138

Validation in: Jochberger S et al., Intensive Care Med 2009 35:489-497

Morgenthaler NG et al., Clin Chem. 2006 Jan;52(1):112-9.


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CT-proAVP – like Vasopressin – is rapidly degraded in vivo

t1/2: few minutes

Morgenthaler et al. Clin Chem 2006


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CT-proAVP – like Vasopressin – is rapidly degraded in vivo

t1/2: few minutes

Morgenthaler et al. Clin Chem 2006


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CT-proAVP – like Vasopressin – is rapidly degraded in vivo

97.5 % percentile normals:

t1/2: few minutes

Morgenthaler et al. Clin Chem 2006


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CT-proAVP – Stimulation via osmoreceptors

CT-proAVP behaves like AVP

Hypertonic saline infusion / thirsting

Hypotonic saline

infusion

Control

n=8

Szinnai et al. JCEM (2007)


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CT-proAVP correlates better with osmolality than Vasopressin

Balanescu S. et.al. JCEM 2011 in press


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CT-proAVP- stimulation via baroreceptors/ hemorrhagic shock, model

CT-proAVP behaves like AVP

Morgenthaler et al. Shock 2007


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Which CT-proAVP levels should be expected in normals?


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CT-proAVP is not age-related

Normal distribution

Morgenthaler NG et al., Clin Chem. 2006 Jan;52(1):112-9


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CT-proAVP levels dependent on gender

Significantly higher levels in males

706 healthy volunteers

Bhandari SS et al, Clinical Science (2009) 116, 257–263


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CT-proAVP: Influence of exercise

Morgenthaler NG et al., Clin Chem. 2006 Jan;52(1):112-9


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CT-proAVP: Influence of exercise

97.5 % percentile normals:

Morgenthaler NG et al., Clin Chem. 2006 Jan;52(1):112-9


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CT-proAVP LIA in the differential diagnosis of Diabetes insipidus


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What is Diabetes insipidus ?

  • Diabetes Insipidus (DI) is a disorder in which there is an abnormal increase in urine output, fluid intake and often thirst (polyuria-polydipsia-syndrome).

  • Urine output is increased because it is not concentrated normally -> the urine is not yellow but pale, colorless or watery.

  • Diabetes Insipidus is divided into three types, each of which has a different cause and must be treated differently. 


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Types of Diabetes insipidus

  • Central Diabetes Insipidus(also known as neurogenic DI): The most common type of DI is caused by a lack of vasopressin.

  • Treatment: various drugs including a modified vasopressin known as desmopressin or DDAVP

  • Nephrogenic Diabetes insipidus(also known as renalDI): is caused by an inability of the kidneys to respond to the "antidiuretic effect" of normal amounts of vasopressin.

  • Treatment: It cannot be treated with DDAVP and, depending on the cause, may or may not be curable by eliminating the offending drug or disease. 


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Types of Diabetes insipidus

  • Central Diabetes Insipidus(also known as neurogenic DI): The most common type of DI is caused by a lack of vasopressin.

  • Treatment: various drugs including a modified vasopressin known as desmopressin or DDAVP

  • Nephrogenic Diabetes insipidus(also known as renalDI): is caused by an inability of the kidneys to respond to the "antidiuretic effect" of normal amounts of vasopressin. 

  • Treatment: It cannot be treated with DDAVP and, depending on the cause, may or may not be curable by eliminating the offending drug or disease. 

Diagnostic Challenge:

All types of Diabetes insipidus also as partial forms existing!


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Types of Diabetes insipidus (II)

  • primarypolydipsia : occurs when vasopressin is suppressed by excessive intake of fluids.

  • most common type of polyuria-polydipsia-syndrome

  • most often caused by an abnormality in the part of the brain that regulates thirst or by psychogenic illnesses (psychogenic polydipsia)

  • difficult to differentiate from central DI because it mimics DI.  

Interested in more?: http://www.diabetesinsipidus.org

Also in French and Spanish language


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Differential Diagnosis of Diabetes insipidus

  • Clinical Challenges: Differential diagnosis of patients with polyuria-polydipsia syndrome

  • State-of-the art diagnosis:

  • 1. Stimulation of AVP release via a Water deprivation test

  • 2.Indirect measurement of AVP release by monitoring of urine osmolality and - volume during water deprivation

  • (ability to concentrate urine).

  • 3. Additional Desmopressin administration to differentiate nephrogenic DI from central DI.

  • Direct AVP measurement becomes not the diagnostic reference standard because of its methological limitations (instability of analyte and uncomfortable assay handling)


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CT-proAVP for Differential diagnosis of Diabetes insipidus

ability to concentrate urine during water deprivation , indirect measurement via urine- volume and – osmolality

ability to respond to desmopressin intake


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Differential diagnosis of Diabetes insipidus

Diagnosis without water deprivation and Desmopressin stimulation possible!

ability to concentrate urine during water deprivation , indirect measurement via urine- volume and - osmolality


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Differential diagnosis of Diabetes insipidus

Diagnosis without water deprivation possible!

Differential diagnosis of partial DI possible

ability to concentrate urine during water deprivation , indirect measurement via urine- volume and - osmolality


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CT-proAVP course during water deprivation

Mean value of CT-proAVP

in primarypolydipsia

Mean value of CT-proAVP

in central DI


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Conclusion:Current state-of -the art - method WDT gives no reliable results in the differential diagnosis of polyuria-polydipsia syndrome!CT-proAVP is superior to the current method of choice and revives the concept of the direct test in the polyuria- polydipsia syndrome.

Superiority of CT-proAVP in diagnosing Diabetes insipidus

Fenske W. et.al. Copeptin in the differential diagnosis of the polyuria- polydipsia syndrome

– revisiting the direct and indirect water deprivation tests. JCEM accepted January 2011


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CT-proAVP: Diagnosis of central DI totalis and nephrogenic DI

in the 1st blood draw

basal CT-proAVP [pmol/l] (fasting, in the morning after 8h dehydration)

< 2.6>20

Sensitivity (%)95100

Specificity (%)100100

Central Diabetes nephrogenic

insipidustotalis Diabetes insipidus

Fenske W. et.al. Copeptin in the differential diagnosis of the polyuria- polydipsia syndrome

– revisiting the direct and indirect water deprivation tests. JCEM accepted January 2011


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Best separation of primary polydipsia and partial central DI (in contrast to current methods including AVP measurements)specificity 100%sensitivity 86%

Differential diagnosis of unclear cases after water deprivation

erum -Na+

Poster:

Fenske W: 14th Annual meeting of the

neuroendocrinology section of the DGE

October 15, 2010 (Munich)

Paper accepted at JCEM Jan. 2011


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2nd blood draw: Stimulated CT-proAVP differentiates safe between central DI partialis and Primary Polydipsia

Index

Δ CT-proAVP [8h-16h] x 1000 [pmol/L/mmol/L]

S-Na+ [16h]

<20>20

Sensitivity (%)10086

Specificity (%) 86100

central Diabetes primary

insipiduspartialispolydipsia

Fenske W. et.al. Copeptin in the differential diagnosis of the polyuria- polydipsia syndrome

– revisiting the direct and indirect water deprivation tests. JCEM accepted January 2011


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Suspicion of Diabetes insipidus with Polyurie-Polydipsie-Syndrome

CT-proAVP basal (in the morning, fasting, after 8h dehydration)

CT-proAVP

>=2,6 - 20 pmol/L

CT-proAVP

<2,6 pmol/L

CT-proAVP

>20 pmol/L

  • Ratio of CT-proAVP-Delta (8 to16h) and Serum-Na+ (16h) = CT-proAVP-Index

Central Diabetes insipidus totalis

Renal Diabetes insipidus

CT-proAVP-Index

<20

CT-proAVP-Index

>=20

Primary Polydipsia

Central Diabetes insipidus partalis

Reliable differential diagnosis of DI with the help of CT-proAVP

CT-proAVP stimulated and Serum-Na+

(after 16 hours dehydration)


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Advantages for the diagnostic routine

  • Significantly higher diagnostic accuracy for all variations of Diabetes insipidus and primary Polydipsia

  • Considerably eased differential diagnosis ofPolyuria-Polydipsia-Syndrome

  • Reduced physical and psychical exposure of the patient due to simplified WDT and redundancy of desmopressin stimulation

  • Support of safe therapeutic decisions with highly sensitive measurement values

  • Overall cost reduction due to reduced complexity, less lab consulting and no prescription of desmopressin


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What about the performance of

the LIA assay?


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Reminder: Why not measure AVP directly?

  • AVP is very unstable in plasma even at -20 °C storage (sample transport frozen or blood collection directly in the lab)

  • AVP is largely attached to platelets

  • AVP assays performed with the required accuracy are available in only a few selected laboratories (non of them FDA cleared)

  • Sample extraction necessary

  • Time to result up to 72 hours

  • Sample volume 1-4 ml plasma

  • No reliable clinical results


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Advantages Thermo Scientific B·R·A·H·M·S CT-proAVP LIA

  • sample volume only 50µl

  • for plasma and serum

  • one-step procedure (time to result 3 hours)

  • stable analyte (at room temperature)

  • highest sensitivity

  • sandwich-immunoassay

  • clinical superiority shown


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CT-proAVP LIA assay parameters

Data taken from IFU (instructions for use)


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