Quantitative particle agglutination assay for point-of-care testing using mobile holographic imaging and deep learning

Particle agglutination assays are widely adapted immunological tests that are based on antigen-antibody interactions. Antibody-coated microscopic particles are mixed with a test sample that potentially contains the target antigen, as...

Sensitivity and Specificity of Treponemal-specific Tests for the Diagnosis of Syphilis

We conducted a systematic review of relevant syphilis diagnostic literature to address the question, “What is the sensitivity and specificity of the treponemal tests currently approved by the Food and Drug Administration (FDA) for the diagnosis of syphilis (by stage)?” There were 16 treponemal assays evaluated: 13 immunoassays and 3 manual assays (fluorescent treponemal antibody absorbed test [FTA-ABS], microhemagglutination assay for Treponema pallidum antibodies [MHA-TP], Treponema pallidum particle agglutination assay [TP-PA]). MHA-TP and FTA-ABS were less sensitive in primary and secondary syphilis than TP-PA; TP-PA is the most specific manual treponemal assay. There is insufficient evidence to recommend one particular treponemal immunoassay (eg, enzyme immunoassays, chemiluminescence immunoassays, microbead immunoassays) over another based on published performance data. For diagnosis of neurosyphilis, cerebrospinal fluid (CSF) TP-PA has similar performance to CSF FTA-ABS in studies with patients with definitive or presumptive neurosyphilis. However, CSF treponemal testing has limitations in its sensitivity and specificity and should be interpreted within the context of the clinical scenario, additional CSF test results and syphilis prevalence.

Syphilis Immunoassay Signal Strength Correlates with Active Infection in Pregnant Women

Objective This study aimed to evaluate the association of ARCHITECT chemiluminescent immunoassay (CIA) signal strength (signal-to-cutoff [S/CO] ratio), with maternal syphilis stage, rapid plasma reagin (RPR) reactivity, and congenital syphilis. Study Design A prospective observational study of reverse syphilis screening was conducted. Pregnant women were screened with CIA. Reactive CIA was reflexed to RPR; particle agglutination test (Treponema pallidum particle agglutination [TPPA]) was performed for CIA+/RPR− results. Clinical staging with history and physical was performed, and disease stage was determined. Prior treatment was confirmed. We compared S/CO ratio and neonatal outcomes among the following groups: Group 1: CIA+/RPR+/TPPA+ or CIA+/RPR−/TPPA+ with active syphilis; Group 2: CIA+/RPR−/TPPA+ or CIA+/serofast RPR/TPPA+, previously treated; Group 3: CIA+/RPR−/TPPA+, no history of treatment or active disease; Group 4: CIA+/RPR−/TPPA−, false-positive CIA. Results A total of 144 women delivered with reactive CIA: 38 (26%) in Group 1, 69 (48%) in Group 2, 20 (14%) in Group 3, and 17 (12%) in Group 4. Mean (±standard deviation) S/CO ratio was 18.3 ± 5.4, 12.1 ± 5.3, 9.1 ± 4.6, and 1.9 ± 0.8, respectively (p < 0.001). Neonates with overt congenital syphilis occurred exclusively in Group 1. Conclusion Women with active syphilis based on treatment history, clinical staging, and laboratory indices have higher CIA S/CO ratio and are more likely to deliver neonates with overt evidence of congenital syphilis.

Evaluation of a Multiplex Fully Automated Treponemal and Nontreponemal (Rapid Plasma Reagin) Assay

ABSTRACTObjectivesIn June 2017, Bio-Rad Laboratories received US Food and Drug Administration clearance for its BioPlex 2200 Syphilis Total & RPR (rapid plasma reagin) assay. It is the first fully automated treponemal/nontreponemal multiplex flow immunoassay, simultaneously detecting Treponema pallidum and reagin antibodies and an RPR titer. We compared the performance of the BioPlex Syphilis Total & RPR assay with the LIAISON Treponema Assay and the manual BD Macro-Vue RPR 18-mm Circle Test.MethodsIn total, 314 serum specimens were tested for treponemal immunoglobulin G/immunoglobulin M and RPR with the LIAISON Treponema Assay, the BioPlex 2200 Syphilis Total & RPR assay, and the manual BD Macro-Vue RPR card test. All discordant results were further tested with the T pallidum particle agglutination assay from Fujirebio Diagnostics.ResultsThe overall percent agreement for the BioPlex assay for treponemal antibodies with the LIAISON Treponema Assay was 96.1%. Sensitivity and specificity for the BioPlex RPR assay were 90.5% and 97.2%, respectively (the manual RPR assay was considered the gold standard).ConclusionsThe BioPlex 2200 Syphilis Total & RPR assay performance was comparable to the LIAISON Treponema Assay and the manual RPR test. Compared with the manual RPR, the automation of RPR testing offered labor savings, objective result reporting, and improved workflow.

Neurosyphilis Manifesting With Bilateral Adie’s Pupil: A Case Report

Background Pupillary abnormalities play an important role in identification of neurosyphilis. Among them, Argyll Roberston pupil is most typical and has been mentioned in many reports and studies. However, papers about Adie’s pupil associated with neurosyphilis are extremely rare. In the present study, we report a case of patient with bilateral Adie’s pupils as isolated manifestation of neurosyphilis. Case presentation we describe a 58-year-old retired Chinese woman with bilateral Adie’s pupils. Further evaluation revealed serologically positive for Treponema pallidum particle agglutination (TPPA), chemiluminescence immunoassays (CLIA) and rapid plasma regain (RPR) test (1:16). The Cerebrospinal fluid (CSF) examination revealed pleocytosis, elevated protein, and positive RPR (1:2), TPPA and CLIA. Final diagnosis of Adie’s pupils associated with neurosyphilis was made and other possible causes were excluded. Cephalosporin was used for treatment due to penicillin allergy. Despite effective anti-syphilis treatment, her pupils remained unchanged. Conclusions Adie’s pupil can be caused by neurosyphilis and is one of the most important pupillary changes in early neurosyphilis. Our study further underscore the necessity of syphilis screening in patients with Adie’s pupil due to further treatment consideration.

Detección de Treponema pallidum subespecie pallidum para el diagnóstico de sífilis congénita mediante reacción en cadena de la polimerasa anidada

Introducción. La sífilis es una enfermedad producida por Treponema pallidum subespecie pallidum cuya incidencia mundial es de 12 millones de casos por año, aproximadamente; de estos, más de dos millones se presentan en mujeres gestantes, siendo la sífilis congénita la complicación más grave de esta infección en el embarazo.Objetivo. Detectar la presencia de T. pallidum subespecie pallidum en muestras clínicas para el diagnóstico de sífilis congénita mediante reacción en cadena de la polimerasa (PCR) anidada y determinar su concordancia con las pruebas serológicas.Materiales y métodos. Mediante PCR convencional y anidada, se amplificaron tres genes diana (polA, 16S ADNr y TpN47) y se confirmaron los productos de amplificación de los genes TpN47 y polA por secuenciación. Las pruebas serológicas empleadas fueron la VDRL (Venereal Disease Research Laboratory), la de reagina plasmática rápida (Rapid Plasma Reagin, RPR) y la de aglutinación de partículas para Treponema pallidum (Treponema pallidum Particle Agglutination Assay, TPPA).Resultados. La sensibilidad para la PCR convencional fue de 52 pg y, para la PCR anidada, de 0,52 pg. La especificidad con los iniciadores TpN47 y polA fue de 100 %; los resultados de la secuenciación mostraron una identidad de 97 % con T. pallidum. En 70 % de las muestras, los resultados de las pruebas serológicas y la PCR anidada concordaron.Conclusión. El gen TpN47 resultó ser el mejor blanco molecular para la identificación de T. pallidum. La PCR anidada se presenta como una alternativa de diagnóstico molecular promisoria para el diagnóstico de sífilis congénita.