The Venereal Disease Research Laboratory (VDRL) test is a microflocculation test for syphilis that uses an antigen containing cardiolipin, lecithin, and cholesterol. For more than 50 years, the preparation of natural cardiolipin and lecithin for this test has been based on the Pangborn method which involves isolating and purifying these components from beef hearts. This process is tedious and time-consuming and results in a variable purity range. In our studies, we found that a VDRL antigen using synthetic tetramyristoyl cardiolipin and synthetic 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (lecithin) was as specific in detecting syphilis as a VDRL antigen made with natural components. In 85% of the cases, we obtained an endpoint titer of 1/2 or 1 dilution more than a titer obtained with a VDRL antigen made with natural components. The use of these pure synthetic compounds, with a purity of 99%, would offer advantages in the standardization and stability of the VDRL antigen. Because this antigen is the basic ingredient in the preparation of nontreponemal reagents such as the rapid plasma reagin, toluidine red unheated serum test, and the unheated serum reagin, the use of this synthetic VDRL antigen should also increase the reactivity of these reagents.
An enzyme-linked immunosorbent assay (ELISA) for detection of immunoglobulin G (IgG) and IgM to cardiolipin, lecithin, and cholesterol (VDRL [Venereal Disease Research Laboratory] ELISA) is described. The specificity of the VDRL ELISA for IgG and IgM was 99.6 and 99.5%, respectively, with sera from 1,008 persons without syphilis. For a group of patients with false-positive results in traditional nontreponemal tests and for patients with autoimmune diseases, the VDRL ELISA for IgG had a higher specificity than the VDRL ELISA for IgM. The sensitivity for IgG and IgM with 118 sera from patients with untreated syphilis was 96.6 and 94.9%, respectively, which was equivalent to the sensitivities of the traditional nontreponemal tests. The performance of the VDRL ELISA was compared with that of an ELISA that uses cardiolipin as the antigen (cardiolipin ELISA). The VDRL ELISA was significantly more sensitive (P less than or equal to 0.01) than the cardiolipin ELISA with 25 sera from syphilis patients but was less sensitive (P less than or equal to 0.01) with 53 sera from patients with autoimmune diseases. The antibody reactivity in the VDRL ELISA could not be absorbed out by lecithin and cholesterol, and the sera from patients with syphilis did not react in an ELISA that uses cholesterol and lecithin as the antigen. This indicates that cholesterol and lecithin, although not antigenic by themselves, may change the structural form of the epitope on cardiolipin so that it becomes more recognizable for antibodies in syphilis and less recognizable for antibodies in autoimmune diseases. The results of the VDRL ELISA were expressed in percentages of the absorbance value of a positive control. The VDRL ELISA gave, without titration of sera, quantitative results that correlated with the quantitative results of the traditional nontreponemal tests obtained by titration. The VDRL ELISA will be well suited for large-scale testing for syphilis and may replace other nontreponemal tests.
OBJECTIVE: To determine the reliability of serological tests in detecting syphilis in a factory worker cohort and examine the impact of concurrent HIV infection on serological tests for syphilis. METHOD: Reactions to non-treponemal and treponemal antigens were tested using sera from a cohort of 3401 factory workers in Harare, Zimbabwe. The participants consented to regular testing for syphilis, by VDRL, and HIV using two ELISAs. All sera from men who were VDRL positive, and a random sample of VDRL negative sera, were tested by RPR, TPHA, and where appropriate FTA-Abs. From the results, men were defined as having no syphilis, active syphilis, incident syphilis, historic syphilis, or giving biological false positive reactions. RESULTS: 709 sera were examined from 580 men. There were 78 cases of active syphilis in the cohort, giving a prevalence of 2.3%, and the seroincidence was 0.25 per 100 person years of follow up. The prevalence of HIV in the cohort was 19.8%. There was a strong association between syphilis, whether active, incident or historic, and HIV seropositivity. With both HIV positive and negative sera the negative predictive values of VDRL and RPR were > 99.9% while the positive predictive value for VDRL (30%) was lower than for RPR (39%). Biological false positive reactions were detected in 0.5% of the cohort, with in most cases a transient rise in VDRL titres up to < 1/16. Higher false positive titres occurred in five men, each of whom was HIV positive. CONCLUSIONS: The VDRL is reliable in detecting possible cases of syphilis even in a community with a high prevalence of heterosexually transmitted HIV. There is need, however, for confirmatory tests. The prevalence of syphilis in this cohort is very low in comparison with other countries in southern Africa, but is consistent with recent data from Harare. Despite a strong association between syphilis and HIV it was clear that syphilis could not be counted as a major factor fueling the HIV epidemic in Zimbabwe.
The role of syphilis and alcohol was investigated in a prospective study of patients with cirrhosis of liver in Uganda, and results were correlated with the histological type of cirrhosis, and serological tests for hepatitis B antigen (HB Ag). Eighteen out of eighty (22·5%) patients with histologically-proven cirrhosis had positive serology for syphilis (VDRL and TPI). A high incidence of alcoholism (80%) and syphilis (60%) was found in patients with micronodular cirrhosis who were all negative for HB Ag. By contrast, HB Ag was detected in 37% of patients with macronodular cirrhosis who had a much smaller incidence of syphilis and alcoholism. Although chronic infection with hepatitis B virus related to HB Ag appears to be an important factor in the pathogenesis of cirrhosis in at least 30% of cases, infection acquired during past treatment for syphilis is not an important cause of the association of syphilis with cirrhosis in this population. Subdivision of patients with cirrhosis into those with and those without a history of severe alcohol abuse showed that the difference between the incidence of syphilis in the two groups is significant statistically. However, evidence of syphilis in association with non-alcoholic as well as alcoholic cirrhosis in this and other previously reported series suggests that the association between the two diseases cannot be entirely explained through the common factor of alcoholism, and other factors may also be responsible.
A urease-based enzyme-linked immunosorbent assay (ELISA) has been developed for the detection of reagin antibodies in serum. Visuwell Reagin (ADI Diagnostics Inc., Rexdale, Ontario, Canada) is a non-treponemal screening test for the serodiagnosis of syphilis which has the benefits of large batch testing, automatability, and objective interpretation of results. Unheated, undiluted sera are incubated in 96-well microtiter plates coated with a modified cardiolipin-lecithin-cholesterol antigen. Antibody bound to the plate is detected by an anti-human immunoglobulin G-urease conjugate. The procedure consists of three steps, with a total test time of 60 min. Visuwell Reagin ELISA was compared with the Venereal Disease Research Laboratory (VDRL) test and the reagin screening test (RST) with the following results. For ELISA versus the VDRL test, the sensitivities for untreated syphilis (n = 37) were 97.3% for both ELISA and the VDRL test, the confirmatory positive values (n = 79) were 84.8% for ELISA and 72.2% for the VDRL test, and the specificities for normal samples (n = 1,327) were 98.8% for ELISA and 99.5% for the VDRL test. For ELISA versus RST, the sensitivities for untreated syphilis (n = 57) were 94.7% for ELISA and 87.7% for RST, the confirmatory positive values (n = 26) were 96.2% for ELISA and 92.3% for RST, and the specificities for normal samples (n = 1,891) were 99.6% for ELISA and 99.3% for RST. The overall concordance values of ELISA with VDRL test and RST were 96.7 and 97.9%, respectively. The specificity of ELISA compared with that of RST may be underestimated, since confirmatory data were not available for all apparent false-positive samples. Visuwell Reagin had increased sensitivity and similar specificity compared with flocculation tests.
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.
A serum Venereal Disease Research Laboratories (VDRL) test was carried out in 216 elderly patients with dementia or “functional” psychiatric illness, or both, as part of a community based screening program. The VDRL test was positive in 13 patients, 11 of whom (5.1 percent) had an actual past or present syphilitic infection as confirmed by the fluorescent treponemal antibody absorption test (FTA-Abs). In six patients (2.8 percent) syphilis was newly detected, and in another two patients previously detected syphilis had been inadequately treated. Only two (0.9 percent) biologic false positive reactors were detected. These results question the belief that aging per se is a common cause of the biologic false positive reaction; and indicate a relatively high incidence of past or present syphilitic infection in geriatric patients with psychiatric illness in the community who have been referred for crisis intervention.
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.
Background and Objectives:
Biological false positive (BFP) reactivity by the Venereal Disease Research Laboratory (VDRL) test used for diagnosis of syphilis is a cause for concern. The use of the VDRL as a screening procedure is challenged by some studies. The aim of this study is to determine the prevalence of BFP reactions in different subject groups and to assess the usefulness of Treponema pallidum hemagglutination (TPHA) test in low titre VDRL reactive sera.
Materials and Methods:
A total of 5785 sera from sexually transmitted diseases (STD) clinic attendees, antenatal clinic attendees, husbands of antenatal cases, peripheral health centres attendees (representing community population) and from patients referred from different OPDs/wards were screened for BFP reactions by the VDRL test. Sera reactive in the VDRL test were confirmed by the TPHA test.
Out of 80 qualitative VDRL reactive sera, 68 had <1:8 titre on quantitation and TPHA was positive in 59 samples, indicating BFP reactivity in 0.2% in all the subject groups. BFP was nil in the community population. The male-to-female ratio of BFP reactions was 2:1. VDRL and TPHA positivity was highest (76%) in the age group of 20-29 years. The seroprevalence of syphilis varied from 0.4% to 3.5% in different patient groups.
The results of this study highlight that the TPHA positivity was high (86.8%) in sera with VDRL titre less than 1:8. Therefore, for the diagnosis of syphilis, it is recommended that a confirmatory test such as TPHA should be performed on all sera with a reactive VDRL regardless of its titre.
Biological false positive; Syphilis; Treponema pallidum hemagglutination; Venereal disease research laboratory
Serological tests can be helpful in diagnosing syphilis. The ideal test would be highly specific in all stages of the disease; it would be 100% sensitive and would revert to negative with treatment, thereby allowing the physician to monitor treatment effect. No single test satisfies these requirements. Being alert to the signs and symptoms of syphilis in all its stages and familiar with the meaning of the common serological tests (VDRL, MHA-TP, FTA-ABS) will help physicians to detect early treatable disease and thus prevent tertiary syphilis or spread to others. This article describes the serological tests used to diagnose syphilis and outlines what to look for if a VDRL is reported as reactive.
syphilis; serology; sexually transmitted diseases
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%.
The counter-immunoelectrophoresis technique with the Reiter protein (RP-CIE) was compared with two complement fixation tests (Kolmer and RPCF) and a flocculation test (VDRL) in sensitivity and specificity. Of the 1,927 consecutive attendants of a venereal disease clinic whose serum samples were used, 250 were considered to be syphilitic. The number of true-positive and false-positive reactions were: 121 and 4 (VDRL), 124 and 2 (Kolmer), 179 and 41 (RPCF), 166 and 16 (RP-CIE). The VDRL and the RPCF combined were more sensitive and less specific than the VDRL combined with the Kolmer. If the RPCF was replaced by the RP-CIE the sensitivity remained the same but the specificity was higher. The RP-CIE scored more positives than the RPCF in untreated cases of primary syphilis. The results argue for substitution of the RP-CIE for the Kolmer in the combination with the VDRL in the serodiagnosis for syphilis. Moreover, the RP-CIE presents the technical advantages of simplicity, speed of performance, and of not being hampered by the anticomplementary nature of the serum sample.
The rapid plasma reagin (RPR) card test manufactured by Beckman Instruments, Inc., was compared, qualitatively and quantitatively, with the Venereal Disease Research Laboratory (VDRL) slide test and the standard RPR 18-mm circle card tests for the serodiagnosis of syphilis. Sera from 638 individuals were used in this study. Two pilot lots and two production lots of antigen were submitted by Beckman Instruments, Inc., for evaluation. Qualitative agreement among the three RPR card tests was 98.1%; between the Beckman RPR card and the VDRL slide tests, 95.0%; and between the reference RPR card and the VDRL slide tests, 95.5%. The Beckman RPR card test was 95.3% specific, whereas the specificities of the reference RPR card and the VDRL slide tests were 98.8% and 96.1%, respectively. Sensitivities of the three nontreponemal tests were: Beckman RPR card test production lots, 94.7%; reference RPR card test, 96.8%; and VDRL slide test, 90.6%. Quantitative agreement +/- 1 dilution among the three RPR card tests was 93.0%, whereas quantitative agreement was approximately 40% when both RPR card tests were compared with the VDRL slide test. We found the Beckman RPR card test comparable to the standard RPR card tests. Therefore, the decision of which test to use for the serodiagnosis of syphilis is at the discretion of the user.
Of 9733 consecutive serological samples received by Portsmouth and Southampton Public Health Laboratories (PHL) and tested for syphilis, 190 (140 from men and 50 from women) gave positive results. Thirty new cases of syphilis were identified. Most sera were tested initially by both a specific antibody test (the Treponema pallidum haemaglutination (TPHA) test) and a cardiolipin test (the Venereal Disease Research Laboratory (VDRL) test). Among the 14 patients whose sera gave VDRL-positive but TPHA-negative results, 12 sera gave false-positive results. The sera of 90 patients gave TPHA-positive but VDRL-negative results; sera from only seven of these patients gave false-positive results. The VDRL test is very unlikely to identify a new case of syphilis where a TPHA test has failed to do so. The results of the survey suggest that the VDRL test should be withdrawn from initial testing for syphilis except where early primary disease is suspected.
The 6,097 blood donors in Seoul area, the 1,883 pregnant women delivered at Severance Hospital and the 5,136 physical examinees were evaluated for VDRL reactivity. Also, the FTA-ABS and TPHA tests were performed on those who were VDRL-positive, and the 19S (IgM)-FTA test were done on the subjects who were reactive for the FTA-ABS and TPHA tests. All the subjects were over the age of 20 and the study period was conducted from January of 1986 through December of 1986. The results are summarized as follows: 1. VDRL-positive rates were 0.5% in the blood donors, 0.6% in the pregnant women and 0.8% in the physical examinees. 2. The quantitative test of VDRL resulted in low titer below 1:4 in 96% of VDRL-positive pregnant women and physical examinees. 3. The 19S (IgM)-FTA test was reactive in 3 of 12 treated subjects (25%) and 4 of 10 untreated subjects (40%). From the results it is clear that the prevalence of syphilis is continually decreasing compared to the mid 1970's and the early 1980's.
OBJECTIVE--To observe the pretreatment VDRL titres in different stages of early syphilis and evaluate the changes in VDRL titre following treatment using different treatment schedules. DESIGN--Retrospective study was carried out by analysing the records of cases of early syphilis treated between 1976 to 1981. SETTING--Armed Forces personnel treated at different service hospitals in India. SUBJECTS--Of 3183 cases of early syphilis treated with different regimens during this period, 1532 were fully followed-up for a period of 30 months. Records of these 1532 cases were analysed. MAIN OUTCOME MEASURES--Assessment of VDRL titres before treatment and during post treatment surveillance period of 30 months. Attainment of non-reactivity of VDRL test in various stages of early syphilis using different treatment schedules was evaluated. RESULTS--Relatively higher titres were observed in secondary syphilis. Following treatment it was observed that VDRL test was still reactive at the end of 6 months in 16.47% of primary, 27.56% of secondary and 18.95% of early latent cases; at the end of 12 months in 11.38% of primary, 17.25% of secondary and 15.79% of early latent cases while at 30 months reactivity was still observed in 6.60% of primary, 8.39% of secondary and 11.58% of early latent cases. CSF was examined in 1173 cases at 6 months, of which one case revealed VDRL reactivity while two cases showed reactivity amongst 1188 CSF examined at 30 months. There has been no significant difference with broad spectrum antibiotics and 2.4 MU benzathine penicillin. Results were better with 4.8 MU benzathine penicillin and procaine penicillin. CONCLUSION--VDRL test appears to be a reliable test for the follow-up of treated patients in early syphilis. Early treatment prevents development of seropositivity in seronegative syphilis while majority of seropositive cases attain seronegativity by 6 months. Higher doses of benzathine penicillin and procaine penicillin accelerate the speed of seroconversion.
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.
BACKGROUND--IgG antibodies from mothers adequately treated for syphilis can cross the placenta and appear in the sera of healthy newborns without infection. In such infants, a false diagnosis of congenital syphilis is often made. We have designed a retrospective survey to determine the time of seroreversion of the serological tests for syphilis (STS) in uninfected newborns born to mothers who were adequately treated for syphilis. MATERIALS AND METHODS--Fifty two seropositive, untreated newborns born to 51 mothers treated for syphilis were studied. The newborns were followed at 1, 3, 6, 9, and 12 months of age until seroreversion was detected. The VDRL test was followed until 12 months in 12 of the 22 newborns who were positive at birth, the TPHA in 21 of the 46 newborns, and the FTA-ABS test in 22 of the 48 newborns. RESULTS--In the first serological tests done within 1 month after birth, the VDRL was positive in 22 newborns (42%), the TPHA in 46 (88%), and FTA-ABS in 48 (92%). The VDRL seroreverted within 6 months after birth in 84%, and within 1 year in 100%. The TPHA test seroreverted in 95% within 1 year after birth. The FTA-ABS test seroreverted in 100% within 1 year after birth. CONCLUSIONS--In most seropositive, untreated newborns born to treated mothers the VDRL became negative within 6 months after birth and the TPHA and FTA-ABS within 1 year. This result is consistent with current Centers for Disease Control (CDC) guidelines. However, although the CDC guidelines are adequate in general, we think that some revision is desirable concerning the IgM test and combination of the test results in order to rule out congenital syphilis in seropositive, nonsymptomatic newborns born to the treated mothers.
The detection of syphilis among blood donors may reveal high-risk sexual behavior, which can go unreported at the time of donor selection and compromise the safety of the donated blood. In Italy, blood is collected, tested, and distributed by transfusion services (TSs), which also perform outpatient transfusions. Although the TSs must screen for syphilis by law, there are no indications of the specific type of method to be used, generating discrepancies in the results obtained by the different TSs. To determine the proficiency of the TSs in screening for syphilis, we performed an external quality assessment (EQA). The EQA was based on two shipments of serum panels; 133 and 118 of the 326 existing TSs participated in the first and second shipments, respectively. Each panel consisted of both positive and negative serum samples. The results confirmed that the use of a single nontreponemal test (the Venereal Disease Research Laboratory [VDRL] and the rapid plasma reagin [RPR] tests) is the least sensitive means of identifying samples that are positive for syphilis antibodies. We also found that the interpretation of the results of manual techniques, such as the RPR test, the VDRL test, the Treponema pallidum hemagglutination (TPHA) assay, and the T. pallidum particle agglutination (TPPA) assay, can vary greatly among different TSs and operators. Total Ig enzyme immunoassays (EIAs) are the most sensitive. However, the determination of syphilis on the basis of the results of a single test is not sufficient for an accurate screening; and all blood units should thus be assessed by two distinct treponemal tests, that is, a total Ig EIA and the TPHA or the TPPA assay.
Fifty-one patients with syphilis were treated with oral doxycycline. A course of the antibiotic treatment consisted of 200 mg of doxycycline daily in two divided doses for 28 days. The courses were repeated three to four times a year with an interval of several months. Quantitative Venereal Disease Research Laboratory (VDRL), Wassermann reaction (WR), and Treponema pallidum haemagglutination assay (TPHA) tests were performed monthly to evaluate the therapeutic effect of doxycycline treatment. The response rate was 100% for primary, 90% for early, 68% for late, and 90% for congenital syphilis in adults. No notable side effects were encountered except for epigastric fullness in one patient, which did not require the treatment to be discontinued. No abnormalities were detected in the results of laboratory tests.
A total of 1,020 serum and plasma specimens were tested using the Venereal Disease Research Laboratory (VDRL), Rapid Plasma Reagin (RPR) card, Reagin Screen (RST) and Fluorescent Treponemal Antibody-Absorption (FTA-ABS) tests. In 257 normal patients, all screening tests were nonreactive; the FTA-ABS test was reactive for one patient. In 588 patients with treated and untreated syphilis, the RST results were 91.7% in agreement with the VDRL and RPR results. In 175 patients with diseases that cause biological false reactions, the RST was 94% in agreement with the other screening tests. The titer of the RST was within one dilution of the corresponding VDRL titer in 91.7% of the 360 speciments tested and within one dilution of the RPR titer in 96.9% of 358 specimens quantitated by both tests.
Seroreactivity in 130 cases of primary syphilis was 91.5% by fluorescent treponemal antibody absorption test, 82.3% by microhemagglutination (MHA-TP test), and 68.5% by the Venereal Disease Reseach Laboratory (VDRL) test. The MHA TP test generally became reactive earlier than the VDRL test and confirmed all reactive and most weakly reactive VDRL results.
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
In this study, we aimed to determine the performance characteristics of toluidine red unheated serum test on cerebrospinal fluids (CSF-TRUST) as compared to venereal disease research laboratory test on cerebrospinal fluids (CSF-VDRL) for laboratory the diagnosis of neurosyphilis.
A cross-sectional study.
Sexually transmitted infections (STIs) clinics.
Participants and methods
CSF and serum samples were collected from 824 individual STD clinic patients who have syphilis and are suspected to progress to neurosyphilis within a 9-month period. CSF-VDRL and CSF-TRUST were performed parallelly on the same day when collected. Treponema pallidum particle agglutination (TPPA) tests were also performed on the CSF and the serum samples, and biochemical analysis of the CSF samples was also performed.
The overall agreement between CSF-TRUST and CSF-VDRL was 97.3%. The reactive ratios of the CSF samples were 22.1% by CSF-TRUST and 24.8% by CSF-VDRL, respectively. All CSF-TRUST-reactive cases were reactive in the CSF-VDRL. Twenty-two samples with CSF-TRUST-negative were tested CSF-VDRL-reactive with low titres (1 : 1 to 1 : 4). Over 97% of the double-reactive CSF samples (CSF-VDRL and CSF-TRUST) had an identical titre or a titre within a two-fold difference. The agreement of CSF-TPPA and CSF-VDRL was 71.9%. Similarly, the agreement of CSF-TPPA and CSF-TRUST was 69.2%.
Our results revealed that CSF-TRUST could be used as an option for CSF examination in settings without CSF-VDRL in place.
Syphilis; Laboratory Methods; China
We evaluated the sensitivity and specificity of a new confirmatory test for treponemal antibodies, INNO-LIA Syphilis (Innogenetics NV, Ghent, Belgium), on a large number of sera from a clinical laboratory. This multiparameter line immunoassay (LIA) uses recombinant and synthetic polypeptide antigens derived from Treponema pallidum proteins. In a single-blinded cross-sectional retrospective study, 289 seronegative sera, 219 seropositive sera, and 23 sera with an indeterminate serological status for syphilis were analyzed. All sera were tested by the T. pallidum hemagglutination assay (TPHA), the immunoglobulin (IgG)-fluorescent T. pallidum absorption assay (IgG-FTA-ABS), and the Venereal Disease Research Laboratory (VDRL) test. In addition, some seropositive samples were analyzed by the 19S-IgM-FTA-ABS test, an enzyme immunoassay (IgM-EIA), and the MarDx immunoblotting assay. Based on a consensus diagnosis derived from conventional serology, all of the sera were classified as positive, negative, or indeterminate, and the results were compared with the findings of the INNO-LIA Syphilis assay. The sensitivity and specificity of the LIA were 100% (219 of 219) and 99.3% (286 of 288), respectively. Compared to TPHA and IgG-FTA-ABS, the new test gave a significantly higher number (P = 0.021 and P < 0.0001, respectively) of correct results than either of the other two tests. The multiparameter INNO-LIA Syphilis assay is a useful confirmatory test for syphilis because it increases the reliability of syphilis diagnosis with respect to current conventional techniques.