Practical Application of Quantitative HiSens Auto Rapid Plasma Reagin Latex Turbidimetric Immunoagglutination for Diagnosing Syphilis; Comparison Analysis between Rapid Plasma Reagin Latex Turbidimetric Immunoagglutination Test and Rapid Plasma Reagin Card Test

Abstract

Background : The purpose of this study was to evaluate validity of quantitative RPR LTIA, HiSens Auto RPR LTIA (HBi Corp., South Korea) and to decide an adequate cutoff value for syphilis screening. Materials and Methods : A total of 549 serums or plasma specimens from patients were tested with RPR LTIA and RPR card tests. Degree of agreement between the two methods was analyzed, and validity of RPR LTIA test was analyzed by receiver operating characteristic (ROC) curves. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), accuracy, and ROC statistics of the RPR LTIA test were analyzed to decide an adequate cutoff value. Results : Agreement analysis showed slight to moderate agreement (k=0.093-0.588, P=0.000). Kappa value had its highest value at the cutoff value of 1.3 and 1.6 (k=0.588, P=0.000). Kappa value at the cutoff value of 1 ranked second (k=0.578. P=0.000). A plot of ROC curve showed a statistically valid result to differentiate between a syphilis test positive group and a syphilis test negative group (AUC=0.92, P=0.000). The cutoff values in RPR LTIA test ranged between 0.65 and 1.15 when both sensitivity and specificity were higher than 80%. Conclusion : HiSens Auto RPR LTIA test showed statistically valid result to differentiate between syphilis test groups. Considering the importance of sensitivity in screening for syphilis and the degree of agreement with RPR card test, the cutoff value of 1 in HiSens Auto RPR LTIA test is thought to be adequate.