Thesis (M.Sc.) - Cairo University - Faculty of Medicine - Department of Pediatrics

Background/aim:There are 2 main types of diabetes inspidius (DI), central DI due to vasopressin deficiency and nephrogenic DI due to nephrons insensitivity to vasopressin. Water deprivation test is the cornerstone investigation in diagnosing and differentiating DI types. The aim of this study was to investigate the efficiency of serum copeptin (part of the vasopressin) in diagnosing and differentiating the types of DI. Materials and methods:Twenty fiveEgyptian children havingDI and 25 healthy control subjects were recruited fromspecialized children'shospital,CairoUniversity and Atfal Masr hospital.Full history and clinical examination were done.Weight, vital signs, 24 hour urine volume, baseline electrolytes, plasma and urine osmolalitywere assessed. Water deprivation tests results were obtained from patient's files. Serum copeptin was performed by ELISA technique. Results:There were significant difference between the DI patients and controls in serum creatinine and potassium (p values 0.036 and 0.003 respectively). While serum copeptin (pg/ml) showed insignificant difference between DI patient's and control subject (P value 0.71). The 25 DI patients were divided into: 19 with central DI and 6 with nephrogenic DI according to water deprivation test. Both groups showed insignificant difference in post dehydration osmolality (p value 0.17), whileboth groups showedsignificant difference in average urine output (ml/h) and average urine osmolality (mosm/l) after minirin intake with p values of 0.002 and 0.002 respectively.Serum BUN, creatinine and plasma osmolality levels were higher in nephrogenic DI withsignificant statistical difference (p values of 0.04, 0.02 and <.001respectively). However serum copeptinshowed insignificant difference between both groups. Conclusion:Serum copeptinmay have poor diagnostic value for diabetes insipidus

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