Construction of a predictive scoring system as a guide to screening and confirmation of the diagnosis of primary aldosteronism.

ABSTRACT

BACKGROUND: Primary aldosteronism (PA) is the most frequent cause of secondary hypertension. In Southern Thailand, the aldosterone-renin ratio (ARR) is only available within a small number of tertiary centres, necessitating need for a simple clinical assessment to determine the requirement for ARR. OBJECTIVE: This study aimed to identify predictive factors for the diagnosis of PA and generate a predictive scoring system (PSS) for use in screening and diagnosis of PA. PATIENTS AND METHODS: A total of 420 patients aged >15 years with paired plasma aldosterone concentration and plasma renin activity values allowing calculation of ARR were identified from the electronic hospital database between 2011 and 2016. RESULTS: The overall prevalence of PA was 16.7% (range; adrenal incidentaloma 5.6% to hypokalaemia 30%). Predictive factors for diagnosis of PA were as follows age <60 years, BMI < 25 kg/m2 , presence of diabetes, ≥3 antihypertensive agents, serum sodium ≥ 141 mmol/L and serum potassium < 3.5 mmol/L. A predictive scoring system (PSS) (range -2 to 13) was generated by the coefficients of the variables with ROC curve AUC 0.87 [95% CI 0.83-0.91]. Using the PSS, a total score <4 provided a robust negative predictive value (sensitivity, 0.97; specificity, 0.48; NPV, 0.99; PPV, 0.27) for PA. In patients at high risk of PA (PAC > 15 ng/dL and PRA < 1.0 ng/mL/hr), a PSS score > 9 had specificity and PPV of 100%, essentially confirming PA in these individuals. CONCLUSION: The proposed PSS for PA will enable more focused and cost-effective use of ARR screening and confirmatory testing. In our cohort, 40% and 42% of patients would not require ARR screening or confirmatory tests, respectively.