Development of a Prediction Model for Patients with Suspected Primary Aldosteronism and an Inconclusive Salt Loading Test

Presentation Number: SUN 514
Date of Presentation: April 2nd, 2017

Marieke S. Velema1, Evie J.M. Linssen1, Ad R.M.M. Hermus1, Hans J.M.M. Groenewoud1, Gert-Jan van der Wilt1, Antonius E. van Herwaarden1, Jacques W.M. Lenders2, Henri J.L.M. Timmers1 and Jaap Deinum*1
1Radboud University Medical Center, Nijmegen, Netherlands, 2Department of Internal Medicine III, University Hospital Carl Gustav Carus, Technical University Dresden, Germany


Diagnosis in patients with a suspicion of primary aldosteronism (PA) is confirmed by a salt loading test (SLT). In case of inconclusive test results the decision about how to manage the patient is usually based on contextual clinical data. Our objective was to create a prediction model to confirm or exclude PA in patients with an inconclusive SLT. We used a retrospective cohort comprised of patients who underwent an SLT between 2005 and 2016 in our university medical center. We included 290 patients of whom 14 had incomplete data. The SLT was inconclusive in 115/276 patients. An expert meeting decided that 45/115 had PA. This resulted in a total of 146/276 patients with PA. Binary logistic regression analysis on variables independently associated with PA resulted in a decision model containing the following continuous predictors: plasma renin concentration (PRC) before SLT, plasma aldosterone concentration (PAC) after SLT, potassium supplementation, and plasma potassium concentration.1 In patients with an inconclusive SLT the model had a sensitivity of 84.4% and a specificity of 94.3%. The positive and negative predictive value were 90.5% and 90.4% in our population. In conclusion, our model may be helpful to decide on how to manage PA patients with an inconclusive SLT. External validation and prospective studies are necessary before implementing this model in clinical practice.

1 Prediction score (p)† = ebx / (1+ebx)

Where bx = 0.55– 0.290*PRC before saline infusion (mU/l) + 0.05*PAC after saline infusion (pmol/l) + 0.07*potassium supplementation prior to SLT (mmol/day) –2.75*plasma potassium concentration prior to SLT (mmol/l)

†p>0.59 indicates PA