Syphilis: Diagnosis Lecture outline •Introduction •Diagnosis in the adult •Interpretation of serological tests •Syphilis/HIV interactions© by author •Diagnosis in the infant ESCMID Online Lecture Library Treponema pallidum © by author ESCMID Online Lecture Library Image: CDC PHIL Treponematoses (Differentiation based on clinical and epidemiological considerations) • Treponema carateum (pinta) – Central America; spread by close contact • skin only • Treponema pallidum subspecies endemicum (non-venereal endemic syphilis (“bejel”) – Middle East, SE Asia; spread by close contact • skin and bone only • Treponema pallidum subspecies pertenue (yaws) – Africa; spread by close© contactby author • skin and bone only • Treponema pallidum subspecies pallidum (syphilis) ESCMID– World-wide; spreadOnline by sexual Lecture intercourse Library • skin, bone, viscera, CNS, congenital infection Stages of syphilis Time after exposure Classification Early (infectious) syphilis 9-90 days Primary 6weeks - 6months Secondary ≤ 1 year (or ≤ 2 years) Early Latent Late (non-infectious) syphilis > 1 year (or > 2 years) Late Latent 3-20 years Tertiary © by authorGummatous Cardiovascular Neurosyphilis ESCMID Online Lecture Library Roles of syphilis testing • Diagnosis of active infection • Screen for infectious syphilis (early stage) • Screen for infection at any stage (early & late) • Confirmatory tests • Provide a guide to treatment status and monitor the efficacy of treatment© by author • Detect neurological involvement (CSF) • DetectESCMID congenital Online infection Lecture Library Lab tests for Syphilis diagnosis • Direct detection of Treponema pallidum • NB Cannot be cultured in vitro • Dark ground microscopy •Fluorescent antibody staining •PCR • Antibody detection • Detects antibodies against pathogenic treponemes •always reported as ‘treponemal’ serology • Incubation period© 9 - 90by days author • Natural history - many decades ESCMID• Suspect neurosyphilis Online - test Lecture serum before CSFLibrary Methods of detecting T. pallidum in primary infection Dark ground Sensitivity Exudate; live treponemes; microscopy 79-97% morphology; dark ground microscope; experienced clinican and observer; genital lesions; 15 mins DFA-Tp Sensitivity Exudate; fixed treponemes; (MoAb to 73-?100% morphology; fluorescent 47KDa microscope; experienced antigen) © by authorobserver; oral and rectal lesions; 30 mins; no kit PCR Sensitivity Exudate; specialised ESCMID Online75-95% Lectureequipment; objective; Library high specificity (T. pallidum subsp.); 2-4 hours; no kit EIA or TPPA © by author ESCMID Online Lecture Library Serological tests I • Non-treponemal tests • Cardiolipin antigen “Reagin” “Lipoidal” • VDRL slide test (read microscopically) • Rapid plasma reagin or carbon antigen test (RPR or VDRL/RPR) • Wasserman reaction (CFT) © by author ESCMID Online Lecture Library VDRL slide test Positive Negative © by author ESCMIDAs seen Online through Lecture a microscope Library © by author ESCMID Online Lecture Library VDRL Carbon antigen test/RPR © by author ESCMID Online Lecture Library Serological Tests II • Treponemal tests • Antigen from Nichols strain of T. pallidum • TPHA (erythrocytes as carrier) • TPPA (gelatin particles as carrier) • TPLA (automated) • EIA/CLIA (native and recombinant antigen) • Immunoblot (Western© by Blot author or recombinant) • FTA-Abs ESCMID• Rapid immunochromatic Online Lecture strip tests Library EIA (T. pallidum enzyme immunoassay) © by author ESCMID Online Lecture Library TPPA (or TPHA) test © by author ESCMID Online Lecture Library What we want in an ideal screening test ? • Sensitive (100%) • Specific (100%) • Simple to perform (automation) • Consistent quality of reagents • Objective reading© by author • Reproducible •ESCMID Cheap Online Lecture Library You don’t always get what you want! Screening with RPR/VDRL • Specificity > 99% • Problem of Biological False Positives (pregnancy, malaria, infectious mononucleosis, hepatitis, connective tissue disease, IV drug abuse) • Sensitivity varies by stage • 70-85% in primary • ~100% in secondary • 60-80% in late stage infection • Prozone © by author • Usually negative after treatment • Cheap and simple • NotESCMID generally automated Online (Mediace?) Lecture Library • Subjective Screening with TPHA/TPPA TPHA • Specificity > 99.5% • Sensitivity • 70-80% in primary • 100% in all other stages (untreated and treated) • antibody persists after treatment (may become negative in HIV) TPPA • Specificity > 99.5%© by author • Sensitivity – 90-95% in primary syphilis • Easier to perform and read than TPHA ESCMID Online Lecture Library TPLA • Automated version (Sekisui Mediace) Screening with EIA • Variety of EIAs • Native vs. recombinant T. pallidum antigens • Screening tests detect total IgG and IgM • Specificity > 99.5% • Sensitivity • 80-85% in primary and 100% in all other stages • Antibody persists after© treatment by author (may become neg in HIV) • ObjectiveESCMID reading Online Lecture Library • Suited to automated testing/ electronic reporting • Can test for other blood borne infections on same analyser • Not suitable for titration (staging/treatment monitoring) Window period • Maximum detection of primary syphilis depends on high index of clinical suspicion • Window of 1-2 weeks when all serological screening tests may be negative • Perform a direct test if there is a lesion • Request EIA for specific IgM and/or © by author • Repeat test 6 weeks later ESCMID Online Lecture Library What to use as a confirmatory test? • Depends on • Resources and test volume • Screening test used • Confirmatory test should be • A treponemal test© byof a differentauthor type (i.e. using different antigens) ESCMID• Equivalent Online sensitivity andLecture specificity Library Predictive value as a measure of the utility of a diagnostic test • Predictive value is influenced by • Sensitivity; specificity; prevalence • Positive predictive value (PPV) • The probability that a positive result is a true result for the infection© by being author tested for • Negative predictive value (NPV) ESCMID• The probability Online that a negative Lecture result isLibrary a true result and excludes the infection being tested for Recommendation for confirmatory testing • TPPA (TPHA) when EIA is used to screen • EIA when TPPA (TPHA) is used to screen • Optimal profile to help stage disease; monitor treatment; and detect re-infection should include • Quantitative VDRL© by author • (Quantitative) TPPA (TPHA) ESCMID• EIA for anti -Onlinetreponemal LectureIgM Library Can we use the immunoblot as a confirmatory test ? • Initially there were problems in defining a positive immunoblot result for tests using native T. pallidum antigen • Line immunoassays using recombinant antigens have overcome these problems • Hagedorn et al J Clin Microbiol 2002; 40: 973-8 • Sensitivity 100% © by author • Specificity 99.3% • Can be useful in clarifying diESCMIDscrepancies Online Lecture Library Serological tests: active infection and staging disease • A VDRL/RPR titre of ≥16 and/or a positive IgM test indicate active disease and the need for treatment – Lower VDRL titres are found in untreated early infection – VDRL may exhibit prozone (false-negative due to v. high Ab levels), particularly in 2° stage, reinfection, HIV co-infection • The EIA IgM is often negative in late syphilis, and VDRL can be negative;© by this author does not exclude the need for treatment ESCMID Online Lecture Library Response to therapy VDRL / RPR Reactivity • Seroreversal rates vary depending on • Pre-treatment titre • Stage of disease • Previous episode of syphilis • Treatment regimen • Decrease in titre (primary and secondary) • Brown et al JAMA 1985; 253: 1296 - 9 • 4-fold at 3 months;© by 8-fold author at 6 months • Romanowski Ann Intern Med 1991; 114:1005 - 9 ESCMID• 4-fold at 6Online months; 8-fold Lecture at 12 months Library • Early latent: 4-fold at 12 months • Patients may become ‘serofast’ at ≤4 (may be higher in HIV) Reinfection • A fourfold increase in titre (confirmed on a second specimen) suggests re-infection or relapse – Frequently reinfection produces a higher titre than first infection AND/OR • IgM becomes reactive again (confirmed on a second specimen) after it© has by become author negative – Watch out for low positive indices which may indicate a ‘blip’ in test sensitivity ESCMID– Not all reinfections Online result inLecture a positive IgM testLibrary Syphilis serology in HIV infection • Very high levels of antibody often produced • Increased risk of prozone phenomenon • "Delayed seropositivity" rather than "Seronegative“ • Titres may not fall as expected after treatment • Conflicting reports, response dependent on: • Previous syphilis; stage; pre-Rx titre; regimen • Change in serological© markers by author for syphilis •20-40% loss of reactivity to one treponemal test •ESCMIDFalse negative FTA Online-abs tests Lecture Library Interpretation of serological tests Screening Confirmatory VDRL IgM Report test test Neg Not done Not done Not done Treponemal antibody not detected but advise repeat if at risk of recent infection. Neg Neg/Pos Neg/Pos Pos Suggests early primary infection. Advise repeat to confirm. Pos Pos Pos Pos Consistent with recent/active treponemal infection. Advise repeat to confirm Pos Pos Pos Neg Consistent with treponemal infection. Advise repeat to confirm Pos Pos Neg Neg Consistent with treponemal © by authorinfection at some time. Advise repeat to confirm Pos Neg Neg Neg Treponemal antibody not detected. ESCMID Online Lecture Library