Application Effect Evaluation Of Three Methods In Detecting Syphilis In Screening Of Blood Donors

Syphilis is a kind of sexually transmitted diseases which hurts human health badly. Recently the incidence of syphilis ascends gradually in China. The pathogeny of syphilis is T.pallidum subspecies pallidum which belongs to Treponema. Human is the exclusive infectant source of syphilis. Some syphilis is congenital and the other is acquired. Congenital syphilis with the name fetus transmitted syphilis causes by fetus infected Treponema pallidum through placenta. It may result in abortion and premature labor in the forepart. In the afternoon it may bring congenital syphilis to the survival. Acquired syphilis infects by sexual intercourse, buss, operation, lactation, blood transfusion and contacting infectant. Its clinical forms include syphilis of the first period, the second period and the third one. People who are infected by Treponema pallidum may produce special antibody against Treponema pallidum and non-special antibody aiming at cardiolipin. Special antibody includes IgM ang IgG. IgM exists for a short time while IgG may persist very long or lifetime. The concentration of IgG is low and it can't prevent reinfection. Non-special antibody called reagin includes lipoid which is released by destructed tissue, and IgM or IgG which is produced through stimulation by lipoid and lipoprotein of Treponema pallidum . The antibody may be detected in many urgent or chronic diseases which are not caused by Treponema pallidum. Special antibody against Treponema pallidum appears earlier than non-special antibody and may persist for a long time or lifetime even after normal cure. Early diagnosis and therapy are very important to prevent the spread of syphilis. Choosing good methods with high sensitivity and speciality is useful to diagnose syphilis. Recently these methods include: RPR, TRUST, ELISA, TPHA and TPPA, et al. Sometimes Western blot and PCR are used. Chinese criterion prescribes that the results of syphilis detection of blood donors must be negative using RPR, TRUST or ELISA. Therefore using sensitive and special methods to detect syphilis is very realistic to enhance blood quality, to prevent transmitting syphilis by transfusion and to guarantee blood safety. Four methods are established to detect syphilis from blood samples of blood donors in the experiments such as semiautomatic RPR detection, automatic ELISA detection and manual TPPA and Fluorescent quantity PCR detection. The optimal way of detecting syphilis for massive screening of blood donors is selected after result analyse and method evaluation.Materials and Methods1,Patients32327 blood samples were collected from Chengdu's Centre of blood from the first ten days of October 2006 to the first ten days of February 2007. All samples were obtained from volunteer donors of blood who passed medical questionnaire and physical check-up according to national criteria and were anticoagulated by EDTA. Internal control materials of Treponema pallidum antibody were used in internal quality control. 2,MethodsAutomatic ELISA detection was established using AT plus 2 automatic sampling instrument, SUNRISE plus software, FAME24/20 automatic enzyme immunoassay instrument and itswell software of quality control and management of blood test. Automatic sampling method was founded using TECAN RSP 150 automatic sampling instrument, while manual detection method was founded using KJ-201BD oscillator in RPR. TPPA was founded using Heidolph board oscillator and x-ray observing screen. Fluorescent quantity PCR detection was established using FTC-2000 fluorescent quantity PCR instrument. With the methods of RPR and ELISA, 32327 samples from blood donors were detected , and then the positive samples were tested by TPPA and Fluorescent quantity PCR. Analysed results and evaluated methods. Statistics method: x~2 test.Results1,Foundation of RPR, ELISA, TPPA and fluorescent quantity PCR to detect syphilisFounded ELISA by automatic sampling and automatic detection successfully. Founded RPR by automatic sampling and manual detection. Founded TPPA and fluorescent quantity PCR . Four methods were used very well.2,Using ELISA to detect syphilis from blood donorsIn 32327 samples from volunteer donors of blood, 174 of them were positive with the method of ELISA. Positive ratio was 5.38‰(174/32327) .3,Using RPR to detect syphilis from blood donorsIn 32327 samples from volunteer donors of blood, 108 of them were positive with the method of RPR. Positive ratio was 3. 34‰(108/32327) .4,Using TPPA to detect samples which were positive with the method of RPR and/or ELISAThere were 201 positive ones which tested with method of RPR and/or ELISA, including 81 positive ones tested by RPR and ELISA, 27 were positive by RPR while negative by ELISA, 93 were negative by RPR while positive by ELISA. Used TPPA to detect 201 positive ones which tested with method of RPR and/or ELISA. 81 positive ones which tested by RPR and ELISA were positive by TPPA. 27 samples which were positive by RPR while negative by ELISA were negative by TPPA. In 93 samples which were negative by RPR while positive by ELISA, 63 were positive by TPPA.5,Using fluorescent quantity PCR to detect samples which were positive with the method of RPR and/or ELISAUsed fluorescent quantity PCR to detect 201 samples which were positive with the method of RPR and/or ELISA. All results were negative.Conclusion1,In the results of 32327 blood samples detecting by RPR and ELISA, the positive ratios using RPR and ELISA are different in statistics with x~2 test (x~2=15.514, P<0.05) .2,Comparing with the assured results of TPPA, RPR may lead to fake positive results and fake negative results, and may leave out syphilis. ELISA may lead to fake positive results and won't lead to fake negative results. ELISA is better than RPR to detect syphilis and more valuable than RPR in the screening of blood donors.3,Taking the factors of methodology and manipulation into account, RPR, TPPA and PCR are not fit for massive screening of blood donors, and ELISA is the optimal method in detecting syphilis for massive screening of blood donors.