[Assessment of Serum IgG and Its Subclasses in Cystic Echinococcosis Patients and Its Application for Diagnosis].

OBJECTIVE: To assess the diagnostic performance of hydatid cyst fluid (HCF) in detecting the anti-HCF IgG and its subclasses IgG1, IgG2 and IgG4 in serum of cystic echinococcosis patients. METHODS: ELISA was used to measure IgG and its subclasses IgG1, IgG2, and IgG4 specific for Echinococcus granulosus HCF, in the sera of 37 cystic echinococcosis (CE) patients and 29 healthy subjects in Huan County, Gansu Province. The receiver operating characteristic (ROC) curves of the four antibodies were analyzed by MedCalc software, referenced with the gold-standard B ultrasonic imaging. The diagnostic performances between the four antibodies were compared using paired z statistics based on the areas under the curve (AUC), and the best diagnostic threshold was determined for each. The sensitivity and specificity for detecting the four types of antibodies were compared using Chi-square test. RESULTS: The AUCs for IgG and its subclasses IgG1, IgG2, and IgG4 were 0.722, 0.919, 0.712, and 0.835, respectively; the AUC of IgG1 was significantly higher than those of IgG (z = 3.629, P < 0.05) and IgG2 (z = 3.292, P<0.05). The sensitivity for detecting IgG, IgGl, IgG2, and IgG4 was 54.1%, 91.9%, 67.6%, and 75.7%, respectively; the sensitivity for IgGl was significantly higher than that for IgG (χ2 = 3.84, P < 0.05), IgG2 (χ2 = 6.80, P < 0.05), and IgG4 (χ2 = 10.16, P < 0.05). The specificity for the four antibodies was 89.7%, 82.8%, 72.4%, and 89.7%, respectively, and no significant difference was found between them. In addition, the sensitivity for detecting IgG4 antibody was significantly higher in CE I-III than in CE IV-V patients. CONCLUSION: The IgG1 antibody shows the highest detection sensitivity by HCF, thus having potential value in diagnosis of cystic echinococcosis.