Children with salt-wasting adrenal insufficiency are managed with glucocorticoid and mineralocorticoid replacement. Measurement of renin activity or concentration alongside blood electrolyte levels is used to monitor the adequacy of mineralocorticoid replacement. Our unit changed from using renin activity to renin concentration and carried out a service review to assess whether this influenced decision-making for fludrocortisone dosing. In total, 50 measurements of plasma renin activity and 50 of renin concentration were analysed on separate cohorts before and after the assay change, with values standardised to multiples of the upper limit of normal (MoU) to allow comparison between assays. We were more likely to increase the fludrocortisone dose for a raised renin concentration than a raised renin activity. The renin concentration MoU was more strongly related to plasma sodium (negatively) and 17α-hydroxyprogesterone (17α-OHP) (positively) than the renin activity MoU. Using a MoU cut-off of 1.5, a decision to increase the dose of fludrocortisone was more likely to be made when using the renin concentration assay compared with the activity assay. Using a cut-off of 40 nmol/L for 17α-OHP, a decision not to change the fludrocortisone dose when 17α-OHP was <40 was more likely when using the renin concentration assay. For both assays, a plasma sodium <140 mmol/L was more likely to lead to a fludrocortisone dose increase, and most likely for the renin concentration assay. Overall, the decision to adjust fludrocortisone dose in this cohort of children with adrenal insufficiency was better supported by the biochemical parameters when based on renin concentration results and clinical status.

患有盐消耗型肾上腺皮质功能不全的儿童可通过糖皮质激素和盐皮质激素替代疗法进行治疗。测量肾素活性或浓度以及血液电解质水平用于监测盐皮质激素替代的充分性。我们的部门从使用肾素活性改为使用肾素浓度，并进行了服务审查，以评估这是否影响氟氢可的松剂量的决策。总共，在测定改变之前和之后，对不同队列进行了 50 次血浆肾素活性测量和 50 次肾素浓度测量，并将值标准化为正常上限 (MoU) 的倍数，以便在测定之间进行比较。我们更有可能因肾素浓度升高而增加氟氢可的松剂量，而不是因肾素活性升高而增加氟氢可的松剂量。与肾素活性 MoU 相比，肾素浓度 MoU 与血浆钠（负向）和 17α-羟基孕酮 (17α-OHP)（正向）的相关性更强。使用 MoU 截止值 1.5，与活性测定相比，使用肾素浓度测定时更有可能做出增加氟氢可的松剂量的决定。使用 17α-OHP 40 nmol/L 的截止值，当使用肾素浓度测定时，当 17α-OHP <40 时更有可能决定不改变氟氢可的松剂量。对于这两种测定，血浆钠<140 mmol/L 更有可能导致氟氢可的松剂量增加，对于肾素浓度测定来说最有可能。总体而言，根据肾素浓度结果和临床状态，生化参数更好地支持了在这组肾上腺功能不全儿童中调整氟氢可的松剂量的决定。