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.     

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.     

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%.     

Comparison of RPR ''teardrop'' card test, VDRL and FTA-ABS tests results on sera from persons with suspected yaws in Columbia.

A small study comparing results of the rapid plasma reagin (RPR) teardrop card test performed in the field, with results of Venereal Disease Research Laboratory (VDRL) and fluorescent treponemal antibody absorption (FTA-ABS) tests performed in the laboratory on venous blood specimens from the same suspected yaws patients was undertaken in Columbia in July 1975. The results suggest that the RPR teardrop card test may be used to screen for infectious, or potentially infectious, yaws patients under field conditions, but that it will not reliably detect patients with VDRL titres of 1:2 or less, or all patients in whom sera are reactive in the FTA-ABS test.     

Comparison of RPR 'teardrop' card test, VDRL and FTA-ABS tests results on sera from persons with suspected yaws in Columbia.

A small study comparing results of the rapid plasma reagin (RPR) teardrop card test performed in the field, with results of Venereal Disease Research Laboratory (VDRL) and fluorescent treponemal antibody absorption (FTA-ABS) tests performed in the laboratory on venous blood specimens from the same suspected yaws patients was undertaken in Columbia in July 1975. The results suggest that the RPR teardrop card test may be used to screen for infectious, or potentially infectious, yaws patients under field conditions, but that it will not reliably detect patients with VDRL titres of 1:2 or less, or all patients in whom sera are reactive in the FTA-ABS test.     

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.     

Influence of genital herpes on results of fluorescent treponemal antibody absorption test.

Both the fluorescent treponemal antibody absorption (FTS-ABS) test and Venereal Disease Laboratory (VDRL) test for syphilis were performed routinely on 113 men with histories of genital ulcerations. The difference in negative VDRL and borderline FTS-ABS results between patients with and without herpes simplex virus in their genital ulcers and no evidence of previous or untreated syphilis was not statistically significant. Furthermore, use of the FTA-ABS test as a confirmatory rather than a screening test eliminates false-positive, borderline, or reactive results in patients with non-syphilitic ulcers.     

Influence of genital herpes on results of fluorescent treponemal antibody absorption test.

Both the fluorescent treponemal antibody absorption (FTS-ABS) test and Venereal Disease Laboratory (VDRL) test for syphilis were performed routinely on 113 men with histories of genital ulcerations. The difference in negative VDRL and borderline FTS-ABS results between patients with and without herpes simplex virus in their genital ulcers and no evidence of previous or untreated syphilis was not statistically significant. Furthermore, use of the FTA-ABS test as a confirmatory rather than a screening test eliminates false-positive, borderline, or reactive results in patients with non-syphilitic ulcers.     

Recent observations on the serology of syphilis.

Routine screening of 404 742 sera by the automated micro-haemagglutination assay (AMHA-TP) and the Venereal Disease Research Laboratory (VDRL) test showed that 9848 specimens gave a reactive result to one of the three assays. Reactive results were confirmed by the fluorescent treponemal antibody absorption (FTA-ABS) test. The possibility of false-positive results varied from 0.04-0.38% of all specimens or from 1.7-15.7% of reactive sera. The VDRL test failed to detect reactivity in 56.54% of sera from patients who had previously been infected with Treponema pallidum. The importance of routine testing by the AMHA-TP is illustrated by the detection of four patients with mesaortitis and two with active neurosyphilis among a selected group of 54 patients who had non-reactive results to the VDRL test. Testing of cerebrospinal fluid specimens by the AMHA-TP test produced more specific results than by the other two tests.     

Specificity of the Treponema pallidum haemagglutination test. Analysis of results.

The automated haemagglutination assay using Treponema pallidum antigen (AMHA-TP) and the Venereal Disease Research Laboratory (VDRL) test were used to examine 330 163 sera. Reactive results were checked by the fluorescent treponemal antibody-absorption (FTA-ABS) test. When isolated reactivity or non-reactivity in the AMHA-TP test was investigated an estimated margin of error of 0.7% probably wrongly non-reactive and 0.008% presumably false non-reactive results were found. These figures were confirmed by randomised FTA-ABS tests on 504 sera with repeat AMHA-TP tests. The latter is therefore still the most reliable and practicable method for mass screening for syphilis.     

Clinical course and treatment of venereal spirochaetosis in New Zealand white rabbits.

Ten sporadic cases of venereal spirochaetosis, caused by Treponema paraluis-cuniculi, were seen in New Zealand white rabbits in two years. An equal number of males and females were affected. Females tended to have milder clinical signs than males. Lesions were usually found on the prepuce in males and the vulva in females, although the anus and skin of the perineum were also affected. Facial lesions were rare. Lesions healed in seven to 28 days in rabbits treated with penicillin. Eight rabbits had antibodies reactive in the Venereal Disease Research Laboratory (VDRL), rapid plasma reagin (RPR), and fluorescent treponemal antibody absorbed (FTA-ABS) tests when the disease was first diagnosed. In several rabbits followed longitudinally, RPR test results became negative two to four months after antimicrobial treatment, VDRL antibody titres diminished but usually persisted at low levels, while FTA-ABS antibodies declined slowly and were still evident 12 months after treatment.     

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.     

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.     

Quantitative evaluation of the FTA-ABS-IgM and VDRL test in treated and untreated syphilis.

Observations made on fluorescent treponemal antibody absorption (FTA-ABS) immunoglobulin M (IgM) titres in patients with untreated early syphilis showed non-reactive or weakly reactive results in patients with primary (one of five cases) and secondary (two of 16 cases) lesions. In patients with primary (19.5%) and secondary (15%) syphilis sera remained reactive with increased titres for more than one year after treatment. The respective figures in the results of the Venereal Disease Research Laboratory (VDRL) test were zero in primary and 20% in secondary syphilis. The non-reactive FTA-ABS IgM results may possibly be explained by competitive inhibition of IgM by immunoglobulin G (IgG). The persistence of reactivity in a comparable percentage has been observed by other investigators (Grin et al., 1974; Wilkinson and Rodin, 1976). The current results therefore suggest that FTA-ABS IgM titres are less reliable for assessing the effect of treatment than the course of the VDRL titres. The phenomenon of a decrease in FTA-ABS IgM titres soon after treatment with a later rise before final non-reactivity is a matter for further investigation.     

Quantitative evaluation of the FTA-ABS-IgM and VDRL test in treated and untreated syphilis.

Observations made on fluorescent treponemal antibody absorption (FTA-ABS) immunoglobulin M (IgM) titres in patients with untreated early syphilis showed non-reactive or weakly reactive results in patients with primary (one of five cases) and secondary (two of 16 cases) lesions. In patients with primary (19.5%) and secondary (15%) syphilis sera remained reactive with increased titres for more than one year after treatment. The respective figures in the results of the Venereal Disease Research Laboratory (VDRL) test were zero in primary and 20% in secondary syphilis. The non-reactive FTA-ABS IgM results may possibly be explained by competitive inhibition of IgM by immunoglobulin G (IgG). The persistence of reactivity in a comparable percentage has been observed by other investigators (Grin et al., 1974; Wilkinson and Rodin, 1976). The current results therefore suggest that FTA-ABS IgM titres are less reliable for assessing the effect of treatment than the course of the VDRL titres. The phenomenon of a decrease in FTA-ABS IgM titres soon after treatment with a later rise before final non-reactivity is a matter for further investigation.     

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.     

An IgM capture enzyme linked immunosorbent assay to detect IgM antibodies to treponemes in patients with syphilis.

A new IgM capture enzyme linked immunosorbent assay (ELISA) was compared with the 19S(IgM) fluorescent treponemal antibody absorption (19S(IgM)FTA-ABS) test for detecting IgM antibodies to treponemes. Serum samples from 180 people, 109 with various stages of untreated syphilis, 45 with treated syphilis, and 26 non-infected, were investigated. In all diagnostic groups of syphilis the reactivity of the IgM capture ELISA was similar to that of the 19S(IgM)FTA-ABS test except in untreated neurosyphilis, for which the IgM capture ELISA was significantly less sensitive. The IgM capture ELISA was very sensitive in congenital (100%, 5/5) and primary (82%, 18/22) syphilis, but less sensitive in secondary (60%, 12/20), latent (53%, 16/30), neurosyphilis (34%, 11/32), and treated (11%, 5/45) syphilis. False positive IgM capture ELISA results were not found in five people who gave false positive Venereal Disease Research Laboratory (VDRL) reactions or in 21 neonates born to mothers adequately treated for syphilis before or during pregnancy. This indicated that the IgM capture ELISA was very specific. The course of antitreponemal IgM reactivity after treatment of early infectious syphilis was followed up in six patients. The quantity of IgM antibody declined in nearly all patients after treatment, but still remained detectable in five patients up to six months after treatment. In contrast, non-treponemal antibodies measured by the VDRL test disappeared in four out of six patients within five months from starting treatment. In conclusion, the IgM capture ELISA may be useful for easy and sensitive detection of IgM antibodies to treponemes in patients with congenital and primary syphilis. A positive test result in these cases indicates that patients should receive treatment if they have not been treated recently. The test is not, however, recommended to replace the VDRL test to monitor patients treated for syphilis.