Development of a novel magnetic particle-based agglutination immunoassay for anticardiolipin antibody detection in syphilis

Abstract

ObjectivesSerological tests of non-treponemal and treponemal types are the most frequently used for syphilis diagnosis. Treponemal tests are available in wide variety of assay formats; however, limited advances have been made for the improvement of conventional non-treponemal tests. The objective of this work was to develop a novel non-treponemal magnetic particle-based agglutination assay (NT-MAA) and evaluate its feasibility for syphilis testing.MethodsCardiolipin was modified and coupled to magnetic microbeads. Serum diluted in phosphate-buffered saline was mixed with cardiolipin-coupled beads and incubated in a round bottom microplate for 90–120 min followed by visual inspection. A panel of reported syphilis (n=127) and non-reactive (n=244) specimens was prepared to evaluate the NT-MAA performance in comparison to conventional rapid plasma reagin (RPR). Treponema pallidum particle agglutination (TP-PA) assay and enzyme immunoassay (EIA) were included. Analytical sensitivity and reproducibility of NT-MAA were also determined.ResultsThe non-treponemal NT-MAA and RPR showed sensitivity of 90.6% and 88.2% and specificity of 96.7% and 100%, respectively. The treponemal TP-PA and EIA yielded sensitivity of 100% and 99.2%, respectively, and 100% specificity by both assays. The per cent agreement between NT-MAA and RPR was 97% (kappa=0.931, 95% CI 0.891 to 0.971). Analytical sensitivity determined with IgM anticardiolipin antibody (ACA) was 2.6 µg/mL for both NT-MAA and RPR, while IgG ACA yielded 0.9 µg/mL and 1.7 µg/mL for NT-MAA and RPR, respectively. Qualitative results of intra-assay and interassay reproducibility revealed 100% consistency for NT-MAA.ConclusionPreliminary evaluation of the novel NT-MAA validated proof of concept using laboratory-characterised syphilis sera and demonstrated performance comparable to RPR. Further validation of NT-MAA using additional specimens with better clinical staging may broaden the scope of developed test for syphilis diagnosis.

Efektivitas Pemeriksaan Serologis Sifilis

“…15,17,21,24 RPR menunjukkan sensitivitas 9,1%-100%, spesifisitas 80,8%-100%, NRP 76,2%-100%, dan NRN 65,5%-100%. 13,16,[18][19][20][21][22]26,27 Selain itu, RPR dibandingkan TPHA memiliki observed percentage of agreement (Po) 88,0%. 20 Berdasarkan stadium sifilisnya, sensitivitas RPR pada stadium sifilis primer jauh lebih baik daripada VDRL, akan tetapi pada stadium sifilis sekunder hasil sensitivitas lebih baik terlihat pada VDRL.…”

“…29,44 Sensitivitas dari RPR, VDRL, dan TP Rapid termasuk dalam kategori tinggi. 12,13,[15][16][17][18][19][20][21][22]24,[26][27][28][29][30][31][32][33][34] Spesifisitas tinggi didapatkan pada TPHA dan TP Rapid. 12,24,[28][29][30][31][32][33][34][35] RPR dan VDRL digunakan sebagai skrining karena sensitivitasnya yang tinggi.…”