Specificity of the FTA-ABS and TPHA tests during pregnancy.

In order to determine whether pregnancy influences the specificity of the fluorescent treponemal antibody absorption (FTA-ABS) and Treponema palidum haemagglutination assay (TPHA) tests, these tests, together with the quantitative fluorescent treponemal antibody (FTA) and Venereal Disease Research Laboratory (VDRL) tests, were carried out simultaneously on 2000 pregnant women who attended for compulsory prenatal screening. In only one patient (0.05% of the total investigated) was a positive result to the TPHA test obtained, the specificity of which it was impossibile to confirm. The FTA-ABS test gave a weakly reactive result of the borderline type but this was found to be non-specific in only four (0.2%) patients. The results of our investigations showed that the specificity of the FTA-ABS and the TPHA tests performed on pregnant women did not differ from the specificity of these tests when carried out on other population groups.     

Syphilis in pregnant women in Mozambique.

To establish the prevalence of syphilis in pregnant women in Mozambique and evaluate present diagnostic methods, 1468 pregnant women in eight of the country's 10 provinces were examined using the Venereal Disease Research Laboratory (VDRL) test. Positive serum samples were also analysed using the Treponema pallidum haemagglutination (TPHA) assay and one group was also analysed using the fluorescent treponemal antibody absorbed (FTA-ABS) test. The prevalence of VDRL seroreactivity was found to be between 4.5% and 14.6%, whereas the prevalence of treponemal disease as verified by TPHA or FTA-ABS tests was between 1.6% and 9.8%. It is concluded that syphilis is relatively common among pregnant women in Mozambique. The predictive value of a positive VDRL test, when adequately performed, was     

Comparison of cardiolipin and treponemal tests in the serodiagnosis of yaws.

Results of the Veneral Disease Research Laboratory (VDRL), rapid plasma reagin (RPR), Treponema pallidum haemagglutination (TPHA), T. pallidum immobilisation (TPI), and fluorescent treponemal antibody absorption (FTA-ABS) tests on sera of 661 children from a region where yaws is hypoendemic are compared. For 107 (16.2%) out of 661 sera the FTA-ABS test was the only one showing reactivity; in these instances the test was weakly reactive (intensity of fluorescence scored as +) and the children had no history and no signs or symptoms of treponemal disease. A solitary, weakly reactive FTA-ABS test result seems to have no clinical significance in these cases. The FTA-ABS test can be used as a confirmatory test for yaws instead of the TPI test, if only the results of sera showing an intensity of fluorescence scored as ++ or more are considered to be positive. There appeared to be no significant differences in the results of the VDRL, RPR, and TPHA tests as screening tests for yaws when the TPI or FTA-ABS tests were used as reference tests.     

Comparison of cardiolipin and treponemal tests in the serodiagnosis of yaws.

Results of the Veneral Disease Research Laboratory (VDRL), rapid plasma reagin (RPR), Treponema pallidum haemagglutination (TPHA), T. pallidum immobilisation (TPI), and fluorescent treponemal antibody absorption (FTA-ABS) tests on sera of 661 children from a region where yaws is hypoendemic are compared. For 107 (16.2%) out of 661 sera the FTA-ABS test was the only one showing reactivity; in these instances the test was weakly reactive (intensity of fluorescence scored as +) and the children had no history and no signs or symptoms of treponemal disease. A solitary, weakly reactive FTA-ABS test result seems to have no clinical significance in these cases. The FTA-ABS test can be used as a confirmatory test for yaws instead of the TPI test, if only the results of sera showing an intensity of fluorescence scored as ++ or more are considered to be positive. There appeared to be no significant differences in the results of the VDRL, RPR, and TPHA tests as screening tests for yaws when the TPI or FTA-ABS tests were used as reference tests.     

TPHA test. Experience at the Clinic of Dermatology, University of Milan.

The results of serological investigations with the treponemal haemagglutination (TPHA) test are reported in a large number of luetic and non-luetic patients. From these the following conclusions can be drawn: (1) The sensitivity of the TPHA test is decreased if the test is carried out with micromethods; however, in our opinion, the same degree of sensitivity can be obtained either with the macromethod at dilution 1/80-1/60 or with micromethods at 1/20-1/40. (2) The sensitivity of this test is high, being similar to that of the fluorescent treponemal antibody absorption (FTA-ABS) test in primary and secondary syphilis and even higher than that of the FTA-ABS test in treated subjects. (3) The specificity of the reaction is high, as demonstrated by examining sera in patients with a negative history and clinical examination together with negative results to Treponema pallidum immobilisation (TPI) and FTA-ABS tests, and by studying biological false positive sera. (4) For the serological screening, it may be sufficient to perform the TPHA test with the 1/20-1/40 micromethod together with the Venereal Disease Research Laboratory (VDRL) test. In patients with suspected syphilis, it is advisable to perform the TPHA test by the macromethod, in combination with the FTA-ABS test.     

TPHA test. Experience at the Clinic of Dermatology, University of Milan.

The results of serological investigations with the treponemal haemagglutination (TPHA) test are reported in a large number of luetic and non-luetic patients. From these the following conclusions can be drawn: (1) The sensitivity of the TPHA test is decreased if the test is carried out with micromethods; however, in our opinion, the same degree of sensitivity can be obtained either with the macromethod at dilution 1/80-1/60 or with micromethods at 1/20-1/40. (2) The sensitivity of this test is high, being similar to that of the fluorescent treponemal antibody absorption (FTA-ABS) test in primary and secondary syphilis and even higher than that of the FTA-ABS test in treated subjects. (3) The specificity of the reaction is high, as demonstrated by examining sera in patients with a negative history and clinical examination together with negative results to Treponema pallidum immobilisation (TPI) and FTA-ABS tests, and by studying biological false positive sera. (4) For the serological screening, it may be sufficient to perform the TPHA test with the 1/20-1/40 micromethod together with the Venereal Disease Research Laboratory (VDRL) test. In patients with suspected syphilis, it is advisable to perform the TPHA test by the macromethod, in combination with the FTA-ABS test.     

Evaluation of the role of the Treponema pallidum immobilisation test in Britain.

After specimens of sera from 100000 patients had been screened by a reagin and Treponema pallidum haemagglutination assay (TPHA) 2.7% required further examination. The fluorescent treponemal antibody-absorption (FTA-ABS) test confirmed either a negative or positive TPHA result in 95% of the samples, so that no further investigations were required. This accounted for 99% of the specimens submitted to the laboratory. Repeat tests on a further sample resolved many of the remaining discrepancies. Only 0.05% of patients, in whom repeat tests confirmed a positive TPHA but a negative FTA-ABS result, benefited from a TPI test.     

Treponema pallidum immune adherence test for serodiagnosis of syphilis. 2: Comparison with glass plate, TPHA, and FTA-ABS tests.

Using sera from 340 patients with syphilis the Treponema pallidum immune adherence (TPIA) test was compared with the glass plate, T. pallidum haemagglutination (TPHA), and fluorescent treponemal antibody-absorbed (FTA-ABS) tests. The results of the TPIA test agreed with those of the glass plate, TPHA, and FTA-ABS tests in 65%, 82%, and 73% of cases respectively. In the quantitative TPIA test no significant correlation with the other tests was observed, and it is, therefore, concluded that the TPIA test has highly individual characteristics. From gel filtration the particular feature of the test was its high sensitivity to the IgM antibody. The TPIA test thus appears to be suitable for estimating antibody in the early stages of the disease.     

Treponema pallidum immune adherence test for serodiagnosis of syphilis. 2: Comparison with glass plate, TPHA, and FTA-ABS tests.

Using sera from 340 patients with syphilis the Treponema pallidum immune adherence (TPIA) test was compared with the glass plate, T. pallidum haemagglutination (TPHA), and fluorescent treponemal antibody-absorbed (FTA-ABS) tests. The results of the TPIA test agreed with those of the glass plate, TPHA, and FTA-ABS tests in 65%, 82%, and 73% of cases respectively. In the quantitative TPIA test no significant correlation with the other tests was observed, and it is, therefore, concluded that the TPIA test has highly individual characteristics. From gel filtration the particular feature of the test was its high sensitivity to the IgM antibody. The TPIA test thus appears to be suitable for estimating antibody in the early stages of the disease.     

Serological tests for syphilis in Saudi Arabia.

A total of 6684 sera were initially screened for syphilis by the Venereal Disease Research Laboratory (VDRL) test and the Treponema pallidum haemagglutination assay (TPHA). Reactive sera from either or both these tests were tested for confirmation by the fluorescent treponemal antibody-absorbed (FTA-ABS) test. VDRL biological false positive reactors were detected in 0.5% of the total sera examined, with 0.4% and 0.8%, respectively, obtained in pregnant women and blood donors. Eight sera (0.1%) were found to be positive in the TPHA test alone. An overall positivity of 2.7% for syphilis was detected, with a 0.85% positivity in antenatal patients. Infection with T pallidum seemed to be more common in men than in women (1.6:1) and predominated in the age group 20-39 years. Serological testing of sera from 26 mother and infant pairs allowed one case of congenital syphilis to be detected by FTA-ABS (IgM) and identified VDRL biological false positivity in seven infants.     

Enzyme linked immunosorbent assays with Treponema pallidum or axial filament of T phagedenis biotype Reiter as antigen: evaluation as screening tests for syphilis.

Enzyme linked immunosorbent assays with an ultrasonicate of Treponema pallidum (TP-ELISA) or axial filament of Treponema phagedenis biotype Reiter (AF-ELISA) were developed to detect treponemal antibody. TP-ELISA and AF-ELISA were compared with the T pallidum haemagglutination assay (TPHA), the fluorescent treponemal antibody-absorbed (FTA-ABS) test, and the Venereal Disease Research Laboratory (VDRL) test for sensitivity and specificity of serodiagnosis of syphilis. A total of 1423 serum samples, 253 from patients with various stages of syphilis, 500 from patients attending a sexually transmitted disease (STD) clinic, and 670 from people without syphilis, were investigated. At all stages of syphilis the sensitivity of the TP-ELISA, the AF-ELISA, the TPHA, and the FTA-ABS test did not differ significantly, except that the AF-ELISA was less sensitive than the TPHA (p less than 0.05) for treated syphilis. In primary syphilis, neurosyphilis, and treated syphilis the TP-ELISA and AF-ELISA were significantly more sensitive than the VDRL test (p less than 0.05). The specificity of all tests was comparable (p greater than 0.05). The TP-ELISA and AF-ELISA appear to be good alternatives to the TPHA as screening tests for syphilis. Because of the easy availability of a well defined antigen the AF-ELISA seems to be better suited for large scale testing.     

Screening for treponemal infection by a new enzyme immunoassay.

A new enzyme immunoassay (EIA, Captia Syphilis-G) for detecting IgG antibodies against Treponema pallidum was evaluated as a screening test for syphilis. When serum samples were tested at a dilution of 1 in 20 (EIA20), the overall agreement between the IgG EIA and serological status based on the T pallidum haemagglutination assay (TPHA) and the fluorescent treponemal antibody absorption (FTA-ABS) test was 99.2% (1310/1321). The sensitivity of the EIA20 was 98.4% (60/61) and the specificity 99.3% (1251/1260). Discrimination between patients with and without treponemal infection was good: the mean EIA20 absorbance ratios (patient/mean low titre positive control results) were 0.49 for antibody negative patients, 3.30 for patients with positive Venereal Diseases Research Laboratory (VDRL) test and TPHA results, and 1.77 for patients with negative VDRL but positive TPHA results. The cut off point for excluding treponemal infection was taken as 0.9. Specimens with ratios of more than 0.9 should be confirmed by the FTA-ABS test and evaluated for specific IgM antibodies to treponemes. When serum samples were tested at a 1 in 50 dilution (EIA50) the sensitivity was lower (80.3%) but the specificity was absolute. The reduction in sensitivity correlated with low absorbance ratios in the patients who were VDRL negative and TPHA positive. The screening performance of the IgG EIA20 is thus comparable with that provided by a combination of the VDRL test and TPHA. The potential for automation makes the EIA an attractive alternative, particularly in larger centres. Alternatively, the test can be performed at a 1 in 50 dilution (EIA50), at which level it is ideally suited for confirming the treponemal status of antibodies in serum samples preselected by positive cardiolipin antigen screening test results.     

A new look at the serology of treponemal disease.

The serology of treponemal disease has become simpler and more rational in recent years, mainly as a result of the widespread adoption of specific antibody tests and the use of monospecific fluorescent antibody procedures which give information about the immunoglobulin class of antibodies. A set of tests which has proved particularly useful in routine diagnosis is the following: quantitative TPHA test, quantitative VDRL test, and monospecific (IgG and IgM) FTA-ABS tests. This combination is especially valuable in the assessment of new patients with positive results to serological tests and in the management of patients with treated syphilis.     

Screening tests for syphilis. A comparison of the Treponema pallidum haemagglutination assay with two automated serological tests.

Two Treponema pallidum haemagglutination assay (TPHA) tests (Wellcome and Fuzizoki) were compared with the automated reagin test and the automated Reiter protein complement-fixation test in a routine screening system. The Wellcome TPHA was shown to lack sensitivity, and it is recommended that it should be used at a lower screening dilution. The Fuzizoki TPHA recorded a significant number of false positive and false negative results, and was therefore inferior to the fluorescent treponemal antibody absorption (FTA-ABS) test as a definitive test for syphilis. It is suggested that the TPHA be used in conjunction with a reagin test to replace some of the more inadequate screening tests currently in use. The automated screening tests were shown to have a similar sensitivity to the TPHA as well as several other advantages; they are recommended for testing large numbers of specimens.     

Screening tests for syphilis. A comparison of the Treponema pallidum haemagglutination assay with two automated serological tests

Two Treponema pallidum haemagglutination assay (TPHA) tests (Wellcome and Fuzizoki) were compared with the automated reagin test and the automated Reiter protein complement-fixation test in a routine screening system. The Wellcome TPHA was shown to lack sensitivity, and it is recommended that it should be used at a lower screening dilution. The Fuzizoki TPHA recorded a significant number of false positive and false negative results, and was therefore inferior to the fluorescent treponemal antibody absorption (FTA-ABS) test as a definitive test for syphilis. It is suggested that the TPHA be used in conjunction with a reagin test to replace some of the more inadequate screening tests currently in use. The automated screening tests were shown to have a similar sensitivity to the TPHA as well as several other advantages; they are recommended for testing large numbers of specimens.     

Reiter haemagglutination test: a screening test for syphilis.

Using an ultrasonicate of the Reiter treponeme as antigen the Reiter haemagglutination test (RHA) was evaluated as a serological test for syphilis. Comparison of the results of the cardiolipin Wassermann reaction, Reiter protein complement-fixation test, the fluorescent treponemal antibody-absorbed (FTA-ABS) test, the Treponema pallidum haemagglutination test (TPHA) (at dilutions of 1/16 and 1/80), and the Venereal Disease Research Laboratory test with those of the RHA showed that the RHA was sensitive (85.8%) and agreed well (85.8%) with the FTA-ABS test result. Simplicity, sensitivity, availability of the antigen, and the very low cost of this test support its use as a first-line screening test for syphilis.     

Reiter haemagglutination test: a screening test for syphilis

Using an ultrasonicate of the Reiter treponeme as antigen the Reiter haemagglutination test (RHA) was evaluated as a serological test for syphilis. Comparison of the results of the cardiolipin Wassermann reaction, Reiter protein complement-fixation test, the fluorescent treponemal antibody-absorbed (FTA-ABS) test, the Treponema pallidum haemagglutination test (TPHA) (at dilutions of 1/16 and 1/80), and the Venereal Disease Research Laboratory test with those of the RHA showed that the RHA was sensitive (85.8%) and agreed well (85.8%) with the FTA-ABS test result. Simplicity, sensitivity, availability of the antigen, and the very low cost of this test support its use as a first-line screening test for syphilis.     

Treponema pallidum immune adherence test for serodiagnosis of syphilis. 3: Clinical significance and evaluation of treatment.

Antibody titres were measured in patients with clinical syphilis, and the effect of treatment on the results of the Treponema pallidum immune adherence (TPIA) test is reported. In the Treponema pallidum haemagglutination (TPHA) test little change in antibody titre occurred after treatment while in the fluorescent treponemal antibody-absorbed (FTA-ABS) test only a slight decrease occurred. The decrease in the antibody titre in the TPIA test was similar to that in the glass plate test, but the findings were different. From the results of gel filtration of sera obtained from patients with syphilis at different intervals after treatment it was apparent that the decrease in antibody titre after treatment mainly concerned the IgM antibody; thus, because of the high sensitivity of the TPIA test to IgM antibody the test is useful in evaluating the effect of treatment.     

Treponema pallidum immune adherence test for serodiagnosis of syphilis. 3: Clinical significance and evaluation of treatment.

Antibody titres were measured in patients with clinical syphilis, and the effect of treatment on the results of the Treponema pallidum immune adherence (TPIA) test is reported. In the Treponema pallidum haemagglutination (TPHA) test little change in antibody titre occurred after treatment while in the fluorescent treponemal antibody-absorbed (FTA-ABS) test only a slight decrease occurred. The decrease in the antibody titre in the TPIA test was similar to that in the glass plate test, but the findings were different. From the results of gel filtration of sera obtained from patients with syphilis at different intervals after treatment it was apparent that the decrease in antibody titre after treatment mainly concerned the IgM antibody; thus, because of the high sensitivity of the TPIA test to IgM antibody the test is useful in evaluating the effect of treatment.     

Biological false positive serological tests for syphilis in the Jamaican population.

A total of 19,067 sera were screened for biological false positive (BFP) reactivity by the Venereal Disease Research Laboratory (VDRL) test. Sera which were reactive in the VDRL test were confirmed by the fluorescent treponemal antibody absorption (FTA-ABS) test. BFP reactions were detected in 0.59% of the general population, 0.72% of pregnant women and 11.8% of patients with systemic lupus erythematosus (SLE). The rate of BFP reactors among pregnant women did not differ significantly from the general population. The female to male ratio of BFP in the general population was 2:1 whilst that in the group of patients with SLE was 8:1. The overall seroprevalence of syphilis was 2.2%.