Optimal Cut Off Point Of Primary Aldosteronism And Its Clinical Characteristics

BACKGROUNDAccording to the epidemiological survey, the prevalence of hypertension in adult was 29.6%, and its a serious threat to people’s life quality. Primary aldosteronism(PA), as one of the most common form of secondary hypertension, its number of cases is growing. In the past, diagnosis of PA was dependent on clinical manifestations, so the rate of missed diagnosis of PA was high. The diagnostic rate was increased gradually as the aldosterone renin ratio was used to diagnose PA. However, there was no uniform standard of optimal cut-off point because of the differences in detecting methods and population. So the optimal cut-off point should be established in accordance with specific population to improve the diagnostic accuracy of PA. Recent studies have found that PA patients exist glucolipid metabolism disorders. What is the difference of glucolipid metabolism between PA and essential hypertension(EH), and how does aldosterone play a role in it remains unclear. Besides, studies showed cardiac hypertrophy was an important risk factor responsible for the cardiovascular events in PA. So the characteristics of cardiac structure in PA patients and its relationship with the lever of aldosterone are worthy further study. This study aims to explore the optimal cut off point of diagnosing PA and research the characteristics of glucolipid metabolism and cardiac structure in PA patients by comparing with EH and clear the relationship with aldosterone.RESEARCH OBJECTSixty-five cases of PA and ninety cases of EH were enrolled which were diagnosed in our hospital from 2006 to 2014. All PA patients had hypertention. Forty-five PA patients were confirmed for aldosterone adenoma or adrenal cortical hyperplasia. The clinical characteristics, imaging examination and hormone test results of the rest PA patients conform to the diagnostic criteria of PA. EH patients were accorded with the diagnosis of hypertention, the blood pressure was more than140/90 mmHg. Cortisol rhythm, catecholamine metabolites, 24-hour urinary protein quantity were measured to rule out the other secondary hypertension, such as cushing syndrome, pheochromocytoma, renal disease, and renal artery stenosis.METHODSThe general information was collected, such as age, sex, duration of hypertention and smoking history of all subjects. The height, weight, waist circumference, blood pressure were measured. Plasma renin activity, angiotensinII, aldosterone(ALD), serum lipid, glycosylated hemoglobin, fasting blood glucose, two hour postprandial blood glucose, serum potassium, corticosteroid rhythm and 24 h urinary potassium, urine microalbuminuria and catecholamine of all the subjects were detected. Selecting 45 patients with pathological diagnosis in PA and 50 EH patients which were matched for the age, gender. The ALD and ratio of aldosterone to renin(ARR) were used to draw the receiver operating characteristic(ROC) curve and obtain the optimal cut-off point of diagnosing PA, and access the sensitivity and specificity of those indexes. Comparing the general information of all the subjects between the two groups, especially analysis the differences in the levels of glycolipid and the cardiac structure change. Statistical analyses The continuous variable in accordance with normal distribution was expressed mean±standard deviation. Difference between PA and EH was analysed by independent sample t test, and comparison of counting data was analysed by χ2 test. ROC curves were used to obtain the optimal cut-off point of ALD and ARR, and access the sensitivity and specificity of those indexes. The correlation between the two variables was analyzed by linear correlation analysis. SPSS 18.0 was used for analysis. P value less than 0.05 was defined as statistical significant.RESULT(1)The ALD and ARR of 95 patients were used to draw the receiver operating characteristic(ROC) curve. The area under the curve(AUC)of upright and decubitus ALD were 0.746 and 0.854, the AUC of upright and decubitus ARR were 0.952 and 0.947, and there was significant differences compared with the reference line covers an area of 0.5. The optimal cut-off point of upright ALD were 0.221ng/ml, with the sensitivity of 0.561, specificity of 0.909, the decubitus ALD were 0.175ng/ml, with the sensitivity of 0.829, specificity of 0.795, upright ARR were19.5ng.dl-1 /ng.ml-1.h-1, with the sensitivity of 0.878, specificity of 0.955, the optimal cut-off point of decubitus ARR were 20.5ng.dl-1 /ng.ml-1.h-1, with the sensitivity of 0.902, specificity of 0.841. The sensitivity of the upright ALD、ARR was lower, the specificity is high, whereas the decubitus ALD、ARR had poor specificity and strong sensitivity.(2)The upright ARR in adrenal aldosterone adenoma was significantly higher than that in adrenal cortex hyperplasia.(3)The age, systolic blood pressure in PA were lower than that in EH group(P<0.001), but the diastolic blood pressure was higher(P<0.001). The gender, smoking history, systolic blood pressure, BMI, and waistline had no obvious difference between the two groups. The lever of TG、FBG、2HPBG in PA were obviously higher than that in EH group(P<0.05). There was a positive correlation between two hour postprandial blood glucose levels and upright or decubitus ALD levels(r=0.268,P=0.033;r=0.401,P=0.001 repectively).(4)The ventricular septal thickness and left ventricular mass index were significantly higher in PA than EH group(P < 0.05), Ventricular septal thickness were positively correlated with upright and decubitus ALD levels(r=0.200,P=0.041;r=0.195,P=0.035 repectively).Conclusion(1)This research obtained the optimal cut-off point of diagnosing PA in our area by radioimmunoassay, and the upright ALD was 0.221ng/ml, the decubitus ALD was 0.175ng/ml, the upright ARR was 19.5ng.dl-1 /ng.ml-1.h-1, the decubitus ARR was 20.5ng.dl-1 /ng.ml-1.h-1. The sensitivity of upright ALD、ARR was poor, but with a strong specificity. Besides, the level of ARR moreover is associated with pathologic characteristics.(2)The glucolipid metabolic disorder of PA was more severe than EH patients, and was related to its ALD level.(3)ALD not only cause metabolic abnormalities, but also promote cardiac remodeling in patients with PA.