Endocrine Abstracts

JOINT843

Background: The current diagnostic methods for syndrome of inappropriate antidiuresis (SIAD) and cerebral salt wasting (CSW), relying on clinical and biochemical indicators are imprecise. As existing gold standard techniques using radioisotope methodologies are confined to research settings due to high costs and limited accessibility, there is an urgent need for novel biomarkers to enhance diagnostic accuracy.

Objective: To evaluate the change in serum copeptin levels, as an early diagnostic tool in children to differentiate SIAD and CSW.

Methods: A prospective observational study was conducted on hyponatremic children (serum sodium ≤ 130 meq/l). Subjects with endocrine disorders, chronic systemic diseases, diarrhea, hypovolemic shock, or those using diuretics were excluded. At baseline, copeptin, NT-proBNP, and fractional excretion of uric acid (FEUA) levels were measured. Subsequently, each subject received 0.9% NS according to their maintenance requirements for six hours. During this period, fluid deficits and polyuria, if present, were managed with fluid replacement. Symptomatic hyponatremia was treated with 3% NS. After six hours, samples were again collected for copeptin and NT-proBNP. The subjects were followed until serum sodium levels normalized to differentiate CSW from SIAD based on FEUA levels.

Results: We studied 15 subjects (73.3% male), of whom 11 were diagnosed with SIAD and four with CSW. The cohort predominantly consisted of patients with tuberculous meningitis (66.67%). Baseline copeptin levels showed no correlation with the degree of hyponatremia (r = 0.126). However, delta copeptin was significantly different between the two cohorts and showed a decrease in the SIAD group [-16.43 (-39.07, -4.57) vs 7.94 (-2.30, 29.80) pmol/l, P = 0.024]. A cutoff value for delta copeptin of -9.62 pmol/l, yielded a sensitivity of 100% and a specificity of 63.6% for CSW (AUC [95% CI], 0.864 [0.665–1.00]). Chronic hyponatremia developed in 2 SIAD subjects (18.18%), and these subjects had lower weight-for-age z-score [-4.48 (0.33) vs. -2.03 (1.34), P = 0.037], lower baseline sodium levels [122 (0.00) vs. 128.31 (2.06), P = 0.001] and higher FEUA [32.78(3.19) vs 14.66(5.11), P = 0.000]. The utility of other biomarkers (delta NT pro-BNP, copeptin/urine sodium and serum uric acid) in this diagnostic algorithm could not be established.

Conclusion: Our study demonstrates the role of delta copeptin as a potential diagnostic biomarker in the evaluation of SIAD vs CSW, although its validity needs to be ascertained in larger studies.