Fluorescent Treponemal Antibody Absorption Assay Research Articles

Comparison of 17 serological treponemal and nontreponemal assays for syphilis: A retrospective cohort study

ObjectivesRapid plasma reagin (RPR) and Treponema pallidum (TP) antibody test kits are often used to diagnose syphilis, although the relationship between their measured values is unclear. We aimed to reveal the relevance of these kits’ results. Design and methodsIn all, 143 sera from 110 patients were tested using 12 TP kits and 5 RPR kits and the results compared. ResultsThe specificity and sensitivity of RPR kits were 81–96% and 95–100%, respectively. The correlation coefficients (0.849–0.934) considerably differed between the manual RPR card test and latex agglutination (LA) assay kits. The following sensitivities were obtained: 82–91% for TP fluorescent treponemal antibody absorption assay (FTA-ABS), TP hemagglutination assay (HA), and TP particle agglutination assay (PA); 94–95% for TP LAs; and 92–100% for chemiluminescent immunoassay (CLIA), chemiluminescent enzyme immunoassay (CLEIA), and immunochromatography assay (IC). Correlation coefficients between TP kits were 0.753–0.974, and the measured values varied. Changes in RPR and quantifiable TP kits were the same for patients with reinfected syphilis and with syphilis under treatment. ConclusionsRPR tests had lower specificity than TP antibody tests. RPR card test and RPR LAs had similar specificity and sensitivity, but their measured values were different. RPR should be measured using automatic RPR LA without setting the upper limit of the reported value. RPR LA should also be standardized. The sensitivity of TP antibody was better in CLIA, CLEIA, and IC than in FTA-ABS, HA, PA, and LA. Therefore, TP antibody kits should be standardized and quantified.

Syphilis in Pregnancy

AbstractSyphilis is a sexually transmitted bacterial disease relevant to pregnancy because it has the potential to cause congenital syphilis if it occurs at any time during pregnancy. An upsurge in cases of syphilis in women and hence congenital syphilis has been reported worldwide recently. 40% of cases can result in spontaneous miscarriages, stillbirth, non-immune hydrops, fetal growth restriction and perinatal death, as well as serious sequelae in liveborn infected children. Pregnancy complications can be avoided by early detection and treatment in the antenatal period. All antenatal women should be screened for syphilis at the first antenatal visit. There is no gold standard for diagnostic test of syphilis. A combination of serological tests consisting of treponemal and a non treponemal test are used for diagnosis. Screening with non-treponemal tests such as rapid plasma reagin or venereal disease research laboratory test combined with confirmation of reactive individuals with treponemal tests such as the fluorescent treponemal antibody absorption assay is the usual cost effective approach. Those at risk should be retested in the third trimester. Treatment during pregnancy should be with penicillin depending upon the stage of the maternal infection. All neonates born to mothers who have reactive nontreponemal and treponemal test results should be evaluated.

Comparison of conventional immunochromatographic assay with new automated-Treponema pallidum hemagglutination assay for screening of syphilis in blood donors

Introduction: Serological tests for syphilis contributed greatly to the detection of Treponema pallidum infection in blood donors and especially in those who were missed during the medical selection. Although several different treponemal assays have been evaluated in India, the debate that which treponemal test-formats would be suitable for a particular blood transfusion service is far from settled. Aims and Objectives: The study was undertaken with an objective of comparing conventional immunochromatographic assay (ICA) with new automated T. pallidum hemagglutination assay (a-TPHA) in over 10,000 consecutive blood donor samples with fluorescent treponemal antibody-absorption assay (FTA-Abs) as the gold standard to resolve the discordant samples. Materials and Methods: The study was conducted in the Department of Transfusion Medicine in a large tertiary care hospital in India. Consecutive blood donors from July 2014 to January 2015 were evaluated simultaneously for antitreponemal antibodies by solid-phase ICA (SD BIOLINE Syphilis 3.0, Alere Medical Pvt. Ltd., USA), a-TPHA (Immucor Diagnostics, USA) and FTA-Abs (Biocientifica SA, FTA-Abs, Argentina). Performances of both the assays were evaluated using statistical tools. Results: A total of 10,129 donor samples were evaluated. A total of 113 (1.1%) donor samples were reactive for syphilis; either on ICA or a-TPHA or both. Ninety-one of these 113 reactive samples were reactive on FTA-Abs, giving seroprevalance of syphilis as 0.9%. a-TPHA was superior to ICA in terms of sensitivity, specificity, positive predictive value, negative predictive value, and Youden's index. Conclusion: The new “a-TPHA” is a superior assay to ICA as the screening assay for syphilis in blood donors.

Evaluation of nonspecific treponemal test rapid plasma reagin in comparison with specific treponemal test immunochromatographic assay for screening healthy blood donors

Introduction: Serological tests for syphilis (STS) contributed greatly to the detection of Treponema pallidum infection in blood donors and especially in those who were not identified during the medical selection. Most of the blood centers use nontreponemal tests due to lesser cost, ease of performance, and their ability to pick up early primary stage infection, despite reported high false positivity. However, increasingly large number of blood centers have begun testing with the treponemal tests such as immuno-chromatographic assay (ICA) which is possibly easier and more objective than rapid plasma reagin (RPR), albeit slightly expensive. It is with this background that we undertook a head-to-head comparison of nontreponemal test RPR with treponemal test ICA in over 10,000 consecutive blood donor samples with confirmation of all reactive and discordant samples by fluorescent treponemal antibody absorption assay (FTA-ABS) as the gold standard. Materials and Methods: The study was conducted in the department of transfusion medicine in a large tertiary care hospital in India. Consecutive blood donors from July 2014 to January 2015 were evaluated simultaneously for antitreponemal antibodies by solid phase ICA (SD BIOLINE Syphilis 3.0, Alere Medical Pvt. Ltd., USA), RPR (Immutrep RPR, Omega Diagnostics, Scotland, UK) and FTA-ABS (Biocientifica SA, FTA-ABS, Argentina). Performances of both the assays were evaluated in statistical terms. Results: A total of 10,200 donor samples were evaluated. There were 10,124 confirmed concordant negatives. Thirty-eight samples were concordant positive. Thirty-eight samples (thirty samples were ICA positive and RPR negative and eight samples were RPR positive and ICA negative) were discordant. The sensitivity of ICA was higher (93%) as compared to that of RPR (66%), whereas the specificity of RPR was higher (83%) than that of ICA (66%). Positive predictive value (PPV) of both the tests was similar while negative predictive value (NPV) of ICA was higher (86%) than that of RPR (60%). Youden's index was 0.81 for ICA whereas it was 0.62 for RPR. Conclusion: ICA has a better sensitivity than the RPR and thus seems to be more appropriate test for screening in blood donors.

Cost effectiveness of enzyme immunoassay and immunoblot testing for the diagnosis of syphilis

The burden of disease and associated health-care costs of syphilis are significant despite widespread screening and treatment. Our objective was to conduct an economic evaluation using a simulation model when comparing enzyme immunoassay (EIA) initial testing and Inno-Lia (IL) confirmatory testing (EIA + IL) with rapid plasma reagin (RPR) initial testing and Treponema pallidum particle agglutination assay (TPPA) and fluorescent treponemal antibody absorption assay (FTA-ABS) confirmatory testing (RPR + TPPA/FTA). Estimates of prevalence, test costs and utilization of services for 2006 were derived from Alberta databases. Estimates of test characteristics were derived from the available literature. The incremental cost-effectiveness ratio was Canadian $461 per additional correct diagnosis (less costly and more effective). EIA + IL is cost-effective when compared with RPR + TPPA/FTA for screening and diagnosis of syphilis.

A 32‐year‐old nursing student with hoarseness and dysphagia to solids

A 32‐year‐old nursing student with hoarseness and dysphagia to solids

False positive reactions in confirmatory tests for syphilis in presence of antiphospholipid antibodies: misdiagnosis with prognostic and social consequences

False-positive reactions in the Venereal Disease Research Laboratory test are well known, whereas a positive fluorescent treponemal antibody absorption assay is rarely thought to be a false positive. The non-recognition of serological false-positive tests for syphilis may have negative prognostic and social implications.

Lumbar Puncture for Evaluation of Latent Syphilis in Hospitalized Patients

To determine the prevalence of abnormal neurologic findings and cerebrospinal fluid abnormalities in hospitalized patients with serologic evidence of latent syphilis. Cross-sectional survey. Consecutively admitted hospital inpatients from an inner-city population were screened for serologic evidence of syphilis with reactive plasma reagin and confirmatory fluorescent treponemal antibody absorption assays. In those with reactive tests, such clinical findings as a history of treatment for syphilis, neurologic abnormalities, presence of human immunodeficiency virus infection, and rapid plasma reagin titer were correlated with cerebrospinal fluid white blood cell count, protein level, and VDRL result. Of 490 consecutive patients, 52 (11%) had serologic evidence of syphilis. Forty-three (83%) of these underwent lumbar puncture. Of the 43, 31 (72%) were seronegative for human immunodeficiency virus and 12 (28%) were seropositive. No patient had a reactive cerebrospinal fluid VDRL test. Cerebrospinal fluid abnormalities were seen in 32% of human immunodeficiency virus-seronegative patients and in 67% of human immunodeficiency virus-seropositive patients. Cerebrospinal fluid abnormalities were not predicted by history of treatment for syphilis, abnormal neurologic findings, or an elevated rapid plasma reagin titer. Cerebrospinal fluid IgG indexes in patients with elevated cerebrospinal fluid protein levels suggested that the protein abnormalities were not caused by local antibody production. Nonreactive cerebrospinal fluid fluorescent treponemal antibody absorption tests suggest that the cerebrospinal fluid abnormalities were not the result of neurosyphilis. There was a high prevalence of cerebrospinal fluid abnormalities in hospitalized patients with latent syphilis detected by routine screening. Because of the nonspecificity of the cerebrospinal fluid findings, routine lumbar puncture for such patients appears to contribute little to the treatment of latent syphilis.

The Diagnostic Dilemma of Otosyphilis: A New Western Blot Assay

Currently, the diagnosis of otosyphilis applies to any patient with otologic symptoms of unknown cause and a positive fluorescent treponemal antibody-absorption (FTA-ABS) test result. However, the FTA-ABS assay can have false-positive results and does not distinguish between active and treated disease. The VDRL test, which has been used to distinguish inactive disease, frequently yields negative results in patients who are nonetheless given the diagnosis of otosyphilis. A new Western blot assay can eliminate the possibility of a false-positive result and can confirm whether the infection is active. This assay was used to diagnose unsuspected active syphilis in a patient believed to have autoimmune ear disease. In three other cases of suspected otosyphilis, the diagnosis was refuted when the Western blot demonstrated that the FTA-ABS result was false-positive or that the infection was inactive.