The Venereal Disease Research Laboratory (VDRL) test has long been considered the best serological test for the diagnosis of neurosyphilis. The goal of this study was to find out if the Rapid Plasma Reagin (RPR) could be an alternative to the VDRL. Cerebrospinal fluid (CSF) and sera samples from patients in the following stages of syphilis were tested: 8 had symptomatic and 16 asymptomatic neurosyphilis, 4 were in the primary stage, 6 had secondary syphilis, and 92 were in the latent stage. We have also studied 61 samples from individuals with treated syphilis and 126 with other neurological diseases than neurosyphilis. All the CSF samples were studied with both RPR and VDRL tests. RPR and VDRL test results were mostly concordant. The specificity of these tests for current neurosyphilis was 99% for the VDRL and 99.3% for the RPR, whereas the sensitivity was 70.8 and 75%, respectively, for the VDRL and RPR. In view of these results it seems to us that the RPR could be an alternative to the VDRL in the diagnosis of neurosyphilis.

In the present study, the performance of an enzyme-linked immunosorbent assay (ELISA) technique (Eti-syphilis-G and Eti-syphilis-M; DiaSorin) for detection of Treponema pallidum immunoglobulin M (IgM) and IgG antibodies for the laboratory diagnosis of syphilis was evaluated. Four hundred forty-one samples were studied. The sensitivity and specificity of the ELISA were 100 and 93%, respectively, compared with the results of a microhemagglutination assay for Treponema pallidum (MHA-TP) and 99.4 and 100%, respectively, compared with the results of the fluorescent treponemal antibody absorption (FTA-Abs) test. The results of the ELISA technique were concordant with those of MHA-TP for 98% of the samples tested, while the rate of concordance with the FTA-Abs test was 99.5%. The sensitivities of the rapid plasma reagin (RPR) test, MHA-TP, and the ELISA in the different phases of syphilis compared with the results of the FTA-Abs test were 92, 88, and 100%, respectively, for patients with primary syphilis; 100% for all tests evaluated for patients with secondary syphilis; 97.2, 99.4, and 100%, respectively, for patients with latent syphilis; and 57.9, 92.6, and 97.9%, respectively, for patients with past treated syphilis. The RPR test was reactive with 12 samples that were negative by all the specific tests. IgM antibodies were most frequently detected by the ELISA for IgM antibodies (32.8%) than by the FTA-Abs for IgM antibodies (28.4%). Detection of these antibodies by the FTA-Abs test and the ELISA for IgM antibodies decreased with the stage of disease (72 and 88%, respectively, for patients with primary syphilis to 17 and 19%, respectively, for patients with early latent syphilis). The high sensitivity and specificity of this ELISA technique during all stages of syphilis, together with the fact that it is a simple, objective, and easily automated method, lead us to believe that it could be used as a screening test for syphilis.

In this study, polymerase chain reaction (PCR) techniques were used to detect Treponema pallidum DNA in samples from patients with latent syphilis. Sixty-nine patients with latent syphilis and 18 with treated syphilis were included. Whole blood, plasma, sera and ear scrapings, totalling 235 samples from patients with latent syphilis, were obtained. Three PCR assays (47-PCR, polA-PCR and M-PCR assays) were performed. The 47-PCR yielded the highest number of positive samples -92/235 (39.1%), followed by M-PCR -90/235 (38.3%) and polA-PCR -73/235 (31.1%). Ear scrapings presented the highest number of positives (47/84 -56%), followed by plasma samples (36/84 -42.9%), whole blood (32/84 -38.1%) and sera (21/84 -25%). In conclusion, we have confirmed that T. pallidum can be found in blood of patients with latent syphilis. The 47-PCR technique was found to be the most sensitive, whereas ear lobe scrapings seem to be the best specimen for detection of T. pallidum DNA in latent syphilis.

The Treponema pallidum particle agglutination technique (TP.PA) was evaluated, in comparison with the Venereal Disease Research Laboratory (VDRL) test, microhemagglutination assay for Treponema pallidum antibodies (MHA-TP), and fluorescent treponemal antibody-ABS (FTA-Abs) test for the diagnosis of neurosyphilis. We have studied 198 cerebrospinal fluid (CSF) samples from patients with syphilis, including neurosyphilis, treated syphilis, and with other neurological manifestations than neurosyphilis. All tests were nonreactive in these last group of patients. In the neurosyphilis patients, sensitivity of the TP.PA was 100%. The performance of this test in CSF from patients with primary syphilis was as good as that of the other tests. In secondary and latent syphilis, the TP.PA results (27 reactive samples/73) were similar to those of the MHA-TP (25 reactive samples/73). In the individuals treated for syphilis, the TP.PA, FTA-Abs, and MHA-TP tests were found to be reactive in eight, six, and eight samples, respectively. In conclusion, it seems that the TP.PA can be used in CSF to diagnose neurosyphilis, although as for other serological tests, interpretation of results should be done in conjunction with other neurosyphilis parameters.

The objectives of this study were to evaluate the reproducibility of a molecular method for the subtyping of Treponema pallidum subsp. pallidum and to discriminate strains of this microorganism from strains from patients with syphilis. We studied 212 specimens from a total of 82 patients with different stages of syphilis (14 primary, 7 secondary and 61 latent syphilis). The specimens were distributed as follows: genital ulcers (n ‫؍‬ 9), skin and mucosal lesions (n ‫؍‬ 7), blood (n ‫؍‬ 82), plasma (n ‫؍‬ 82), and ear lobe scrapings (n ‫؍‬ 32). The samples were assayed by a PCR technique to amplify a segment of the polymerase gene I (polA). Positive samples were typed on the basis of the analysis of two variable genes, tpr and arp. Sixty-two of the 90 samples positive for polA yielded typeable Treponema pallidum DNA. All skin lesions in which T. pallidum was identified (six of six [100%]) were found to contain enough DNA for typing of the organism. It was also possible to type DNA from 7/9 (77.7%) genital ulcer samples, 13/22 (59.1%) blood samples, 20/32 (62.5%) plasma samples, and 16/21 (76.2%) ear lobe scrapings. The same subtype was identified in all samples from the same patient. Five molecular subtypes (subtypes 10a, 14a, 14c, 14f, and 14g) were identified, with the most frequently found subtype being subtype 14a and the least frequently found subtype being subtype 10a. In conclusion, the subtyping technique used in this study seems to have good reproducibility. To our knowledge, subtype 10a was identified for the first time. Further studies are needed to explain the presence of this subtype in Portugal, namely, its relationship to the Treponema pallidum strains circulating in the African countries where Portuguese is spoken.