Background: Diabetes insipidus (DI) is a recognised complication of pituitary surgery, with current diagnosis requiring clinical observation aided by plasma and urine electrolytes and osmolalities. Copeptin, a 39 amino acid glycopeptide secreted in equimolar quantities to ADH, is a stable surrogate marker of ADH release and has potential to facilitate prompt diagnosis of post-operative DI. This assay has been shown to accurately predict which patients are likely to develop DI following pituitary surgery. We aimed to trial use of copeptin as a predictor of post-operative DI risk in our centre.
Objective: To determine whether copeptin analysis can be used to predict which patients are at risk of developing DI following transsphenoidal adenomectomy (TSA).
Methods: 44 patients undergoing TSA had samples taken for copeptin pre-operatively, and subsequently at day 1, day 2, day 8, and week 6 post-TSA. Results from patients who developed post-op DI (based on clinical assessment, urine and plasma biochemistry and the need for treatment with DDAVP) were compared to those who did not. Patients with any evidence of pre-operative DI were excluded.
Results: Of 44 patients assessed, eight were clinically determined to have developed DI. Differences were observed between patients with DI and those without in post-operative samples. Of note, there was a significant difference at day 1 post-operation (P=0.025 on KruskalWallis test), with no samples in the DI group exceeding 3.5 pmol/l (100% sensitivity, 52.9% specificity at this cut off).
Conclusion: We confirm that early post-operative copeptin analysis in TSA patients can help to predict the risk of developing diabetes insipidus. In this setting, co-peptin is a useful rule-out test in patients with values above a defined threshold, which may facilitate earlier decision making and shorter hospital stays.