Endocrine Abstracts

JOINT1454

Background: Plasma renin is measured in paediatric patients with salt-wasting adrenal insufficiency (AI) to assess the efficacy of mineralocorticoid (MC) replacement. Plasma renin is recommended as a useful marker to monitor MC replacement and can be measured as either plasma renin concentration (PRC) or activity (PRA). Our department currently measures PRC using immunoassay in paediatric patients, and PRA using LC-MS/MS in adults.

Objective: Here, we sought to compare the clinical utility of PRC and PRA concentrations in paediatric patients with AI taking MC replacement.

Methods: Samples from patients less than 18-years old (n=129, m:f=69:60) requested for PRC were selected randomly. PRC was measured using the IDS-iSYS chemiluminescence immunoassay, PRA was measured by LC–MS/MS. The PRC and PRA values for each sample were reviewed using published reference ranges and categorised into low, normal and high results. Samples which showed disagreement between PRC and PRA results were divided into patient groups. Samples collected from patients attending the adrenal clinic were clinically reviewed by local endocrinologists to determine if MC dosing would differ based on PRC or PRA results.

Results: Of the samples analysed, 96 (74%) exhibited concurrence between their PRC and PRA interpretation. Samples that displayed disagreement (n=33, 26%) included 17 collected from adrenal clinic patients. Of these, eight resulted in a different clinical decision concerning MC replacement based on PRA compared to PRC. In each of these instances, adjustments to MC dose was strongly supported by serum sodium and blood pressure centiles when based on PRA. In several instances, PRC had been overlooked by clinicians and MC dose had been adjusted in preference to other conventional parameters such as blood pressure and serum electrolytes. Thus, PRA provided reassurance that clinicians had correctly assessed MC replacement.

Conclusions: Using the current methodology and normative ranges, our investigation found PRA performed superiorly to PRC for assessing MC replacement in paediatric patients, based on supporting biochemical and clinical parameters. Our results indicated that use of PRA may help to standardise practice when assessing MC replacement, which would have immediate patient benefit through improved blood-pressure and electrolyte control. Further work is planned to corroborate these results in a wider pool of patients.