9. MHA-TP
It uses sensitized sheep erythrocytes coated with T. pallidum
(Nichol’s strain), which agglutinate with anti-treponemal IgM
and IgG antibodies.
15. ENZYME IMMUNOASSAYS
• They can be used to detect IgM, IgG or combined.
• They use recombinant antigens of treponemas.
• They are the most sensitive (94.7%–99.1%) and specific (100%) of
all treponemal tests, particularly in secondary syphilis.
• They are amenable to automation, removing the variation and
subjectivity of the human reader.
• They use several different formats, including (i) antibody class
capture, (ii) sandwich capture, and (iii) competitive assay.
• IgM-specific assays can assist in distinguishing between early and
late infections.
16. HIGH PREVALENCE
Non-Treponemal test to
screen current infection
Treponemal test to confirm presence
Non-Treponemal test
to monitor prognosis
LOW PREVALENCE
Treponemal test to screen
current / past infection
Non-Treponemal test to
screen current infection
Non-Reactive Reactive
Different Treponemal test
to confirm presence
TESTING ALGORITHM
17.
18.
19.
20.
21.
22. CONGENITAL SYPHILIS
• All infants born to mothers who have reactive nontreponemal
and treponemal test results should be evaluated for congenital
syphilis.
• A quantitative nontreponemal test should be performed on
infant serum and, if reactive, the infant should be examined
thoroughly for evidence of congenital syphilis.
24. REFERENCES
1. Bhushan Kumar, Sexually Transmitted Infections.
2. King and Nicole, Sexually Transmitted Diseases.
3. Vinod K Sharma, Sexually Transmitted Diseases & AIDS.
4. James H. Jorgensen (editor) et. al., Manual of Clinical Microbiology.
5. The laboratory diagnosis of syphilis. Can J Infect Dis Med Microbiol.
2005;16(1):45-51.
Editor's Notes
Chemiluiniscence immunoassays are also treponemal tests
VDRL, RPR, USR, TRUST
POC = Point of Care
Reiter’s strain of T. Pallidum is ised.
Sandwitch capture is inferior to other two formats.
IgM-specific EIAs have sensitivities ranging from 88 to 90% in primary syphilis, 76 to 100% in secondary syphilis, and 19 to 69% in early latent syphilis.
For low disease prevelance, reverse testing first by treponemal testing and then by non-treponemal testing is done. if EIA is used for screening, then an RPR test should be performed on all EIA reactives, and a second treponemal test such as TP-PA or FTA-ABS should be used for confirmation if the RPR test is reactive.