This document outlines the syphilis testing algorithm and reporting procedures used in antenatal screening. It describes a multi-step process where an initial EIA/CLIA screening test is followed by confirmatory TPPA/TPHA and RPR tests to determine if a sample is positive, negative, or inconclusive. Inconclusive results require a repeat sample in 2 weeks and may be sent to a reference laboratory. All results must be reported within 8 days to allow timely clinical evaluation and treatment if needed. The goal is to accurately detect syphilis infection status while avoiding false results and ensuring pregnant women receive appropriate care.

1. Syphilis – antenatal screening
algorithm and reporting
Ruth White

2. 2
Syphilis testing algorithm
Syphilis EIA / CLIA
Positive Negative
TPPA / TPHA and RPR
TPPA / TPHA
Positive
TPPA / TPHA and RPR
Negative
Treponemal antibody not
detected
No evidence of Treponemal
infection
Inconclusive result
Ask for a repeat
specimen in 2 weeks
time to look for
evolution of markers
Treponemal antibody
detected
(result consistent with
Treponemal infection
at some time)
Treponemal antibody
detected
(result consistent with
recent or active
Treponemal infection)
RPR
titre
RPR
titre < 1:32
Day 1 – receipt of sample
in the laboratory
Day 8 – reporting of
screening results

3. Interpretation and Management
EIA/CLIA (Total) TPPA/TPHA RPR Clinical comments for reports
1 NEGATIVE Not necessary •Treponemal antibody not detected
•No evidence of treponemal pallidum infection
•Repeat if at risk of recent infection
2 POSITIVE or
Equivocal
POSITIVE NEGATIVE
titre <1:32
•Treponemal antibody detected
•Results consistent with treponemal infection at
some time
•Refer urgently for clinical evaluation
3 POSITIVE or
Equivocal
POSITIVE POSITIVE
titre ≥1:32
•Treponemal antibody detected
•Results consistent with recent or active
treponemal infection
•Refer urgently for clinical evaluation
4 POSITIVE or
Equivocal
NEGATIVE NEGATIVE* •Inconclusive result: repeat specimen
required after 2 weeks. If the same result is
achieved, sample to be sent to reference
laboratory. A report will be issued when the
reference laboratory report is received.
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4. A positive RPR, with a negative TPPA/TPHA is an unusual result and both
tests should be repeated in the first instance. If the result is confirmed a
repeat specimen should be requested, and if the same result is achieved
the sample should be sent to the reference lab.
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5. Key Points
• The recommended screening test is an enzyme immunoassay (EIA) or
chemiluminescent immunoassay (CLIA) detecting treponemal IgG and IgM.
• May be insensitive in very early treponemal infection i.e. a false negative
result may be seen.
• An inconclusive result- a positive/equivocal screening test but negative
TPPA/TPHA may be due to:
a false positive EIA/CLIA-be caused by cross-reacting antibodies in
the woman’s blood. In low prevalence populations,
such as pregnant women in the UK, most initial
screen reactive results will be false.
very early infection
past infection with loss of TPPA
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6. Inconclusive Results
• If a positive result in the screening test is not substantiated by confirmatory
tests, the results are inconclusive. A second sample should be requested to
be sent 2 weeks later and if the result is the same this should undergo
further investigation, in-house if the expertise is available, or via the
reference laboratory. The result will be reported after completion of in-
house testing or on receipt of the result from the reference laboratory.
• A confirmed positive result on the repeat specimen requires immediate
referral to the IDPS MDT
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7. Reporting Results
• Results should not be reported until confirmatory tests are performed and a
conclusion reached about the complete set of results. Interim results must
not be reported as they can cause confusion.
• A rapid service for confirmatory testing must be provided to avoid delays in
reporting and to meet the standard for turnaround times. Confirmed positive
screening tests must be reported directly to the IDPS MDT within 8 days of
sample receipt in the screening laboratory (standard 4). This is to enable
recall of the woman within 10 working days of the positive result (standard
5).
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8. Workshop
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To consider:
• Is the algorithm easy to understand
• Are the comments clear
• When to refer to reference laboratory- is this explained and does it fit
with your practice
• How to manage inconclusive results