Abstract 431: A Novel Score System for Primary Aldosteronism Screening, PUK2 score: Combination of Urine pH and Serum Uric Acid and K+ Levels

Abstract

Background: Hypokalemia is not a sensitive marker of primary aldosteronism (PA) , and method for screening PA by routine clinical parameters has not yet been established. Objective: We examined whether serum uric acid (UA) or urine pH alone, or their combination with serum K+ level is usable for PA screening . Design and Setting: Cross-sectional analyses were retrospectively performed on consecutive patients who visited a single general hospital from April 2012 to September 2013. Participants: Entry criteria were age <75 years old, hypertension and presence of data on serum aldosterone (ng/dL) and renin activity (ng/mL/hr). Exclusion criteria were use of aldosterone blockers, ACE inhibitors, angiotensin receptor antagonists, diuretics, beta-adrenergic blockers, steroids or UA-lowering drugs and diagnosis of secondary hypertensions other than PA. Main Outcome Measures: Diagnosis of PA was made in accordance with the guideline of Japanese Society of Hypertension: patients with aldosterone-to-renin activity ratio (ARR) > 20 and one or more positive results in captopril challenge test, furosemide-upright test, saline infusion test and/or ACTH stimulation test. Results: We enrolled 103 patients (PA = 29, essential hypertension [eHT] = 74). PA has lower serum K+ (3.5±0.32 vs 3.8±0.23 mEq/L, p<0.001, mean ± S.D.), higher urine pH (6.6±0.83 vs 6.1±0.62, p<0.001) and lower UA (5.6±1.6 vs 6.5±1.2 mg/dL, p=0.004) compared with those in eHT. Urine pH≧ 7.0 and UA < 6.0 mg/dL were selected as optimum cutoffs for diagnosis of PA by ROC curve analysis. Multivariable logistic regression analysis indicated that high urine pH, low UA and hypokalemia (K < 3.5 mEq/L) were independently associated with PA. Using the cutoff values, we developed a score system, PUK2 score, which is derived from the sum of point values of PA predictor; 1 point was assigned to low UA and to high urine pH and 2 points were assigned to hypokalemia. The prevalence of PA in the patients with PUK2 score of 0, 1, 2 and 3~ was 5.0%, 31%, 37%, and 83%,respectively. Furthermore, the likelihood ratio in patients with PUK2 score of 0 was 0.13 (95%CI: 0.034-0.52). Conclusions: PUK2 score is easy to use and useful for screening PA in hypertensive patients.