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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

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?

  • 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?


What is Vasopressin

and

where is it produced?


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-


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


What is the physiological role of Vasopressin?


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


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


Vasopressin in stress situation

Myocardialinfarction

STRESS

AVP

ACTH

Cortisol


Why not simply measure Vasopressin?


Vasopressin

Quantification of Vasopressin is difficult


Vasopressin

Receptor

Vasopressin

Quantification of Vasopressin is difficult


Vasopressin

Receptor

Vasopressin

Vasopressin

Platelets

Quantification of Vasopressin is difficult


Protease

Vasopressin

Vasopressin

Receptor

Vasopressin

Vasopressin

Platelets

Quantification of Vasopressin is difficult


Protease

Vasopressin

Vasopressin

Receptor

Vasopressin

Vasopressin

Platelets

Quantification of Vasopressin is difficult

Further problem: very unstable ex vivo (even frozen)


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


Prohormone processing and assay

Signal

Vasopressin

CT-proAVP

Neurophysin II

Morgenthaler NG et al., Clin Chem. 2006


Signal Peptidase

Prohormone processing and assay

Signal

Vasopressin

CT-proAVP

Neurophysin II

Vasopressin

CT-proAVP

Neurophysin II

Morgenthaler NG et al., Clin Chem. 2006


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


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


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


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


Is CT-proAVP produced together with Vasopressin?

Do both analytes show the same kinetics in vivo?


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.


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

t1/2: few minutes

Morgenthaler et al. Clin Chem 2006


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

t1/2: few minutes

Morgenthaler et al. Clin Chem 2006


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

97.5 % percentile normals:

t1/2: few minutes

Morgenthaler et al. Clin Chem 2006


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)


CT-proAVP correlates better with osmolality than Vasopressin

Balanescu S. et.al. JCEM 2011 in press


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

CT-proAVP behaves like AVP

Morgenthaler et al. Shock 2007


Which CT-proAVP levels should be expected in normals?


CT-proAVP is not age-related

Normal distribution

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


CT-proAVP levels dependent on gender

Significantly higher levels in males

706 healthy volunteers

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


CT-proAVP: Influence of exercise

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


CT-proAVP: Influence of exercise

97.5 % percentile normals:

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


CT-proAVP LIA in the differential diagnosis of Diabetes insipidus


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. 


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. 


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!


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


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)


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


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


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


CT-proAVP course during water deprivation

Mean value of CT-proAVP

in primarypolydipsia

Mean value of CT-proAVP

in central DI


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


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


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


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


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)


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


What about the performance of

the LIA assay?


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


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


CT-proAVP LIA assay parameters

Data taken from IFU (instructions for use)


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