1 Copeptin Test A lot more Correct as Diagnostic for AVP Deficiency

— Even so, this examination was far more complicated, with much more side consequences, researchers take note

by Kristen MonacoSenior Staff Writer, MedPage Currently November 15, 2023

Arginine-stimulated copeptin was inferior to hypertonic saline-stimulated copeptin in the analysis of arginine vasopressin (AVP) deficiency, formerly known as central diabetic issues insipidus, the CARGOx trial confirmed.

Of 158 people with polydipsia and hypotonic polyuria or a regarded analysis of AVP deficiency who underwent both tests, diagnostic accuracy was 74.four% (95% CI 67.-80.6) for arginine-stimulated copeptin and ninety five.6% (ninety five% CI 91.one-ninety seven.eight) for hypertonic saline-stimulated copeptin, documented Julie Refardt, MD, PhD, of University Healthcare facility Basel in Switzerland, and colleagues.

Notably, 72% of the clients most popular screening with arginine as in contrast with hypertonic saline, they wrote in the New England Journal of Drugs.

Though adverse occasions ended up usually gentle for both of those checks, the most common facet effects were thirst, gentle headache, and vertigo, which have been additional powerful and far more regular with the hypertonic saline check.

Even so, whilst the arginine-stimulation exam is less complicated and has a greater side-impact profile than the hypertonic saline test, its dependability has been in problem, observed John Newell‑Price, PhD, of the University of Sheffield in England, in an accompanying editorial.

“The arginine-stimulation check is clear-cut in that it necessitates a short intravenous infusion and sampling at sixty minutes for copeptin,” he defined. “In contrast, the hypertonic-saline examination is much more cumbersome and demands bolus doses, for a longer period infusions, and recurring tests of venous samples for plasma or serum sodium levels until the ranges access a lot more than 149 mmol for each liter, at which position sampling for copeptin is executed.”

Since hypertonic saline is an irritant, it also necessitates great venous access for administration. On prime of that, some of the fluid hundreds and electrolyte shifts involved with it could be contraindicated in some sufferers, these kinds of as individuals with heart failure or epilepsy.

“Supplied the simplicity of the arginine-stimulation exam, it is a shame that it was discovered to be inferior,” Newell-Price tag wrote.

Refardt instructed MedPage Now that while simplicity and aspect consequences could be a trade-off, obtaining a reputable diagnostic exam is important for the suitable cure and avoidance of possibly severe side consequences owing to a completely wrong diagnosis. “If executed the right way, [hypertonic saline-stimulated copeptin] is also a safe and sound exam. Nonetheless, arginine stimulation can even now be used as a to start with simple test to diagnose in excess of 50 % of the patients.”

Newell-Price additional that medical professionals ought to hold their people in intellect when employing these tests in scientific exercise. “Not just about every client who provides with hypotonic polyuria needs to undergo stimulation tests,” he wrote. “For instance, in sufferers with pituitary or hypothalamic disease, specifically with gentle hypernatremia, the diagnosis of partial or finish AVP deficiency is very very likely, and an analysis of matched plasma and urine osmolalities or basal copeptin amounts may perhaps be adequate for prognosis.”

On the other hand, for patients with no prior diagnosis or contraindications, hypertonic saline is the way to go in order to differentiate concerning AVP deficiency and most important polydipsia, he observed.

For this international noninferiority examine158 people (sixty seven% women of all ages) underwent diagnostic analysis with hypertonic saline stimulation on one particular day and with arginine stimulation on an additional working day. These copeptin assessments, that includes a polypeptide that is released as aspect of ordinary AVP secretion, had been proven after the when generally utilized oblique h2o deprivation check was identified to have small diagnostic precision.

The closing diagnoses, made by two endocrinologists three months immediately after the assessments, were being based mostly on prespecified cutoff levels for copeptin of 3.8 pmol/L immediately after sixty minutes for arginine and four.9 pmol/L as soon as the sodium amount was more than 149 mmol/L for hypertonic saline.

A stimulated copeptin degree considerably less than two.7 pmol/L indicated total AVP deficiency, a level of two.seven to four.nine pmol/L indicated partial AVP deficiency, and a level of extra than 4.nine pmol/L indicated principal polydipsia.

Of the 158 clients who underwent the two exams, forty four% had been diagnosed with AVP deficiency and 56% were being diagnosed with main polydipsia.

“Exploratory analyses of knowledge-derived greatest copeptin cutoff values did not expose any substance change in effectiveness,” the authors mentioned.

However, an arginine-stimulated copeptin at a benefit of 3. pmol/L or less led to a analysis of AVP deficiency with a specificity of 90.nine% (ninety five% CI eighty one.7-95.7), whilst levels of additional than 5.2 pmol/L led to a prognosis of key polydipsia with a specificity of 91.4% (ninety five% CI 83.7-95.six).