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Official Journal of the Italian Society of Dermatology and Sexually Transmitted Diseases
Indexed/Abstracted in: EMBASE, PubMed/MEDLINE, Science Citation Index Expanded (SciSearch), Scopus
Impact Factor 1,014
Online ISSN 1827-1820
Alessi E., Scioccati L.
Università degli Studi di Milano Istituto di Scienze Dermatologiche IRCCS Ospedale Maggiore - Milano
Background. Microhemagglutination (MHA-TP) test and passive particle agglutination (TP-PA) test are widely used methods of indirect agglutination for the detection and titration of specific antibodies directed against Treponema pallidum. Gelatine particles are the carrier of the treponemal antigens in the TP-PA test, while in other kits the red blood cells of sheep utilized as carrier in the original MHA-TP test are now replaced by avian or pidgeon red blood cells.
Methods. In order to establish whether the type of carrier used affects the results achieved by these reactions or not, 80 sera of syphilitic patients and 80 control sera, including 20 biological false positivities for cardiolipin antigen, were tested at the same time, by the same laboratory technician, and up to the titre with 4 commercially available indirect agglutination kits manufactured utilizing the above mentioned carriers of the treponemal antigens. The same procedure was also used to examine 20 additional sera, which could not be evaluated in the original MHA-TP test because of spontaneous agglutination of unsensitized red blood cells of sheep.
Results. Control sera gave negative results with all kits. The number of primary syphilis sera found to be seropositive showed a progressive increase using sheep cells, avian cells, pidgeon cells or gelatine particles as carrier of the treponemal antigens. In the sixty sera from secondary, latent or treated syphilis, the mode of the differences between antibody titres obtained with red blood cells of sheep and the other methods showed a one-fold dilution increase with avian cells or pidgeon cells, and a three-fold dilution increase with gelatine particles. Finally, all the sera that could not be evaluated with the original MHA-TP test could be valuated with the other reactions.
Conclusions. In conclusion, the study demonstrated that the replacement of red blood cells of sheep with avian or pidgeon cells as carrier of the treponemal antigens in the MHA-TP test increases sensitivity only slightly and that therefore the kits manufactured using the alternative carriers can be used to control the decrease of the titres after therapy not only in new patients but also in patients previously followed with the original MHA-TP test. In our view the same can not be done for the TP-PA reaction, which on the contrary could be advantageously utilized as a screening test in all new patients thanks to its very high sensitivity.