THURSDAY, Nov. 16, 2023 (HealthDay News) — Arginine vasopressin (AVP) deficiency is more accurately diagnosed with hypertonic saline-stimulated copeptin than with arginine-stimulated copeptin among adults with polyuria polydipsia syndrome, according to a study published in the Nov. 16 issue of the New England Journal of Medicine.

Julie Refardt, M.D., Ph.D., from the University Hospital Basel in Switzerland, and colleagues conducted a noninferiority trial involving adults with polydipsia and hypotonic polyuria or a known diagnosis of AVP deficiency to undergo diagnostic evaluation with hypertonic-saline stimulation and with arginine stimulation on different days. The final diagnosis was made by two endocrinologists independently with use of clinical information, treatment response, and hypertonic-saline test results.

A total of 158 patients underwent the two tests: 44 and 56 percent received the diagnosis of AVP deficiency and primary polydipsia, respectively. The researchers found that the diagnostic accuracy was 74.4 and 95.6 percent for arginine-stimulated copeptin and hypertonic saline-stimulated copeptin, respectively (estimated difference, −21.2 percentage points). Seventy-two percent of patients preferred testing with arginine versus hypertonic saline. Arginine-stimulated copeptin at a ≤3.0 pmol/L yielded an AVP deficiency diagnosis with specificity of 90.9 percent, and levels of >5.2 pmol/L yielded a diagnosis of primary polydipsia with specificity of 91.4 percent.

“For the diagnosis of AVP deficiency, arginine-stimulated copeptin was inferior to hypertonic saline-stimulated copeptin, although arginine-stimulated copeptin was preferred by the trial patients,” the authors write.

Laboratory measurement of copeptin was funded by Thermo Fisher Scientific.

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