COPeptin Evaluation in argininevasopressin Deficiency post transsphenoidal surgery (COPED study).

PURPOSE: Copeptin is an emerging biomarker for polyuria-polydipsia syndrome. Postoperative copeptin levels may predict acquired arginine vasopressin deficiency (AVP-D). This prospective study evaluated the diagnostic performance of serum copeptin for predicting postoperative AVP-D after transsphenoidal surgery (TSS). METHODS: Copeptin was measured preoperatively, immediately after surgery (periextubation, T0), upon first ward arrival (T1), daily until discharge, and at week 2. Delta copeptin was calculated as the percentage change from T0 to T1. RESULTS: Of 53 patients, 23 (43.4%) developed AVP-D, including 4 (7.5%) permanent and 19 (35.8%) transient cases. The AVP-D group showed significantly lower delta copeptin (median  -38% vs. +66%, p < 0.001), day 2 (median 3.1 vs. 4.0 pmol/L, p = 0.021), and week 2 levels (median 2.5 vs. 3.2 pmol/L, p = 0.021) compared with the non-AVP-D group. Delta copeptin (area under the curve 0.826, p = 0.001) demonstrated the best diagnostic performance for AVP-D with an optimal cutoff of < -10% (sensitivity 100%, specificity 76.2%). All AVP-D patients exhibited negative delta copeptin. Week 2 copeptin (area under the curve 0.891, p = 0.011) predicted permanent AVP-D best with an optimal cutoff of < 2.6 pmol/L (sensitivity 100%, specificity 66.7%). CONCLUSIONS: Delta copeptin—the change in copeptin levels from T0 (periextubation) to T1 (2–4 h post-surgery)—predicted AVP-D after TSS. We recommend measuring copeptin immediately after surgery and repeat at 2–4 h. Patients with positive delta copeptin were unlikely to develop AVP-D. A copeptin value > 2.6 pmol/L at week 2 ruled out permanent AVP-D.