Construction of a Predictive Scoring System as a Guide to Screening and Confirmation of the Diagnosis of Primary Aldosteronism

Noppadol Kietsiriroje; Rawipas Wonghirundecha; Onnicha Suntornlohanakul; Robert D. Murray

Disclosures

Clin Endocrinol. 2020;92(3):196-205. 

In This Article

Abstract and Introduction

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.

Introduction

Primary aldosteronism (PA) is the most common cause of secondary hypertension where its prevalence varies between 1% and 20%.[1,2] Left untreated PA is associated with greater cardiovascular adverse events than observed in patients with essential hypertension, whereas treatments either surgical or medical translate into event rates comparable to essential hypertension.[3] Regrettably, only a small proportion of patients with PA are recognized and treated.[4]

Since the first introduction of the Endocrine Society Guideline 2008,[5] there has been increasing recognition of the importance of the diagnosis of PA in Southern Thailand. Within a medical system with limited resources, there remain several barriers to provide an accurate diagnosis. Plasma aldosterone concentration (PAC) and plasma renin activity (PRA) assays are not widely available or remain unvalidated. Endocrinologists able to perform confirmatory diagnostic tests and surgeons performing laparoscopic adrenalectomy are limited, and adrenal venous sampling (AVS) remains scarce.

The current study aimed to explore the prevalence of PA among patients who met the criteria for PA screening according to the 2008 Endocrine Society Guideline, to identify the predictive factors for PA diagnosis and to create a scoring system utilizing demographic and routine biochemistry for case detection in a resource-limited setting where PAC and PRA assays are not readily available.

The Endocrine Society released an updated version of their guideline in May 2016.[6] Many of the recommendations of the 2008 guidelines remained unchanged; however, the updated guideline recommended screening for PA in patients with sleep apnoea and hypertension and that a confirmatory test of PA was not necessary in those patients with spontaneous hypokalemia, PRA level below detection plus a PAC >20 ng/dL.

Comments

3090D553-9492-4563-8681-AD288FA52ACE

processing....