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Rapid Diagnostic Tests for Syphilis A Preliminary Review of the U. S. Clinical Data

Rapid Diagnostic Tests for Syphilis A Preliminary Review of the U. S. Clinical Data. M Sutton, S Zackery, C Ciesielski, M Zajackowski, M Santana, C Langley, L Bernard, V Pope, M Fears, R Johnson, L Markowitz. Background.

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Rapid Diagnostic Tests for Syphilis A Preliminary Review of the U. S. Clinical Data

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  1. Rapid Diagnostic Tests for SyphilisA Preliminary Review of the U. S. Clinical Data M Sutton, S Zackery, C Ciesielski, M Zajackowski, M Santana, C Langley, L Bernard, V Pope, M Fears, R Johnson, L Markowitz

  2. Background • Syphilis is diagnosed in the U.S. by a nontreponemal screening test and a treponemal confirmatory test. • on-site RPR plus offsite treponemal test, OR • RPR and treponemal tests are sent offsite (turn-around time up to 1 week or more). • Rapid immunochromatographic (ICS) diagnostic tests: • treponemal-based tests • can provide results in 15 minutes • may potentially be of use in non-traditional settings • Rapid ICS tests for syphilis are not FDA-cleared for use in the US. • A U.S. based study was conceived to evaluate these rapid diagnostics for syphilis.

  3. Multi-site study of rapid diagnostic syphilis assays of persons attending STD clinics in high syphilis morbidity areas • Cross-sectional study • 3 ICS strips included vary by which Treponema pallidum antigens are present on the test band region • Two U.S. sites are currently evaluating the performance of 3 rapid diagnostic strips

  4. ICS Strip

  5. Immunochromatographic Strip (ICS)Rapid Diagnostics for Syphilis Interpretation of Results II • Membrane strip based immunoassay • Test procedure • Recombinant T. pallidum antigen is coated on the test band region. • Sample is placed on application pad and reacts with antigen-colloidal gold conjugate. • If T. pallidum antibody is present an antigen-antibody-antigen gold complex will form (evident by line in the test area). • Line should always appear in control region. Application Test Control Absorbent Pad Line Line Pad Positive Sample II Negative Sample I Inconclusive

  6. Objectives • To evaluate ICS test performance using finger stick, whole blood, serum, and plasma specimens compared to RPR and TPPA • To compare ICS test performance with serum at local sites and CDC • To evaluate ICS test performance by syphilis stage of disease

  7. Methods I • Enrollment- consenting adults age 18 or older • Finger stick done for point-of-care testing on 1 ICS test • Blood drawn for whole blood, serum, and plasma ICS testing at local sites and serum for CDC testing for 3 ICS tests • Data collection questionnaire includes clinical assessment of syphilis stage of disease, if applicable • Persons tested and treated for syphilis if needed according to established standard of care. • ICS tests are for investigational purposes only.

  8. Methods II • Data analyzed using Epi-Info and SAS • Results reported by comparing to clinical standard of both RPR and TP-PA results • Sensitivity= positives/ RPR (+) TP-PA (+) • Specificity= negatives/RPR (-) TP-PA (-) • Syphilis case definitions

  9. Results (Demographics) • N=383 • 64% male • 47% African-American • 32% White • 18% Latino • Reactive RPRs=24 • Titers < 1:8=8 (33%) • Titers ≥ 1:8=16 (67%) TP-PA R NR TOTAL R RPR NR TOTAL

  10. Results: Test performance (sensitivity)of ICS at local sites, by specimen type, compared to RPR and TP-PA

  11. Results: Test performance (specificity)of ICS at local sites, by specimen type, compared to RPR and TP-PA

  12. Results: Test Performance on Sera, Local Sites vs. CDC Laboratory, compared to RPR and TPPA Sensitivity Specificity

  13. Results: Point-of-care ICS (Finger stick) compared to RPR and TP-PA • Overall (any RPR titer and reactive TP-PA) • Sensitivity=17/17 (100%) • Specificity=324/327 (99.1%)

  14. Conclusions • There is a broad range of sensitivities and specificities for the 3 ICS tests in whole blood, serum, and plasma. • Test performance for sera locally is very comparable to test performance at CDC. • The ICS point-of-care (finger stick) data show sensitivities of 100% and specificities of over 99%. • ICS tests are performing well to date with various stages of disease.

  15. Limitations • Treponemal tests are unable to differentiate between active and previously treated syphilis. • Interval analysis only; more data needed.

  16. Summary & Future Steps • Some rapid diagnostic tests show promising performance as screening tests for syphilis in the United States. • These ICS tests require few supplies and can potentially be used in both traditional clinical settings as well as non-traditional settings. • Data collection is ongoing.

  17. S Zackery C Ciesielski M Zajackowski M Santana C Langley L Bernard V Pope M Fears R Johnson L Markowitz J Braxton J Chapin J Lewis S Berman J Douglas B Litchfield CDC DASTLR Local Public Health Departments Acknowledgments

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