| Objective: To investigate the changes of urinary aquaporin-2 (AQP-2) water channel protein concentrations in patients with congestive heart failure, and explore the correlation among urinary aquaporin-2 , cardiac functional grade, left ventricular ejection fraction (LVEF) and blood N terminal pro-brain natriuretic peptide (NT-proBNP), evaluate the diagnostic value of urinary aquaporin-2 detection for congestive heart failure, analyze the relationship between urinary aquaporin-2 and heart function.Methods: According to the NYHA cardiac functional grading method, 116 patients with congestive heart failure were divided into three groups as follows: gradeⅡ(32 cases ), gradeⅢ(46 cases ) and gradeⅣ(38 cases ). The control group consisted of 30 normal subjects. LVEF was examined by echocardiography. The patients'blood and urine samples were collected within 24 hours after the echocardiography measurement. Serum concentration of NT-proBNP was detected by electrochemiluminescence immunoassay (ECLIA). And urinary AQP-2 concentration was measured by enzyme-linked immunosorbent assay (ELISA).Results: 1. The concentration of urinary AQP-2 in patients with congestive heart failure was higher than that in the control group (423.9±354.3 pmol/ml vs. 39.0±25.8 pmol/ml, P<0.05). The urinary AQP-2 levels were significantly different among the three congestive heart failure groups (192.6±135.7 pmol/ml, 395.0±234.3 pmol/ml and 689.2±444.5 pmol/ml, P<0.05). From cardiac functional gradeⅡto gradeⅣ, the concentrations of urinary AQP-2 were gradually increased. 2. Urinary AQP-2 concentrations were significantly different among various LVEF level groups (199.0±144.9 pmol/ml, 423.2±262.1 pmol/ml, and 899.6±322.0 pmol/ml, P<0.05). With the decrease of LVEF, urinary AQP-2 concentrations were gradually increased. 3. Urinary AQP-2 concentration was positively correlated with cardiac functional grade and serum NT-proBNP concentration respectively (r=0.58, P<0.05; r=0.85, P<0.01), while the concentration of urinary AQP-2 was negatively correlated with LVEF (r=-0.75, P<0.05). 4. Area under the receiver operating characteristic (ROC) curve of AQP-2 was 0.941 (P<0.01); when cutoff point was 76 pmol/ml for diagnosing congestive heart failure, the diagnostic sensitivity, specificity and accuracy of urinary AQP-2 were respectively 87.9%, 80.0% and 86.3%. Area under the ROC curve of serum NT-proBNP was 0.959 (P<0.01). when cutoff point was 204 pg/ml, the diagnostic sensitivity, specificity and accuracy of NT-proBNP were 92.2%, 73.3% and 88.4% respectively. No statistical significance between NT-proBNP and AQP-2 in terms of the diagnostic parameters (P>0.05). 5. Compared with single test of NT-proBNP or AQP-2, the parallel combined tests of NT-proBNP and AQP-2 increased the diagnostic sensitivity and negative predictive value to 100%, but the diagnostic specificity was decreased (P<0.05); The serial combined tests increased the specificity to 90.0%, but the diagnostic sensitivity and negative predictive value were decreased(P<0.05). No statistical significance between the combined tests and the single test in other diagnostic parameters (P>0.05).Conclusions: 1. The urinary AQP-2 level was elevated in heart failure patients, and the concentrations of urinary AQP-2 were gradually increased with the ascending of cardiac functional grade. 2. Urinary AQP-2 concentration was positively correlated with cardiac functional grade and serum NT-proBNP concentration respectively, while the concentration of urinary AQP-2 was negatively correlated with LVEF. The urinary AQP-2 concentration may reflect the severity of heart failure. 3. The diagnostic sensitivity, specificity and accuracy of urinary aquaporin-2 were similar to those of serum NT-proBNP, AQP-2 may serve as a valuable marker in diagnosing congestive heart failure and evaluating the cardiac function. 4. Various combined testing methods of NT-proBNP and AQP-2 may increase the diagnostic sensitivity or specificity.
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