Test Summary Utilization Guidelines

Syphilis Diagnostic TestingReverse Algorithm

Clinical Use Aids in the diagnosis of active Treponema pallidum infection

Clinical BackgroundPCL Alverno uses a “reverse” algorithm for syphilis testing in which the first step in the testing algorithm is a treponemal specific multiplex flow immunoassay (MFI) to detect IgM and IgG antibodies. If the results are negative, syphilis is unlikely. If a recent infection is suspected, repeat testing in 4-6 weeks should be performed. If the results are positive a confirmatory, nontreponemal specific assay (RPR) is performed. If the RPR is positive, the results are consistent with past or present syphilis. Treatment is indicated unless the patient has been previously treated. If the titer increases by 4 fold or more, retreatment is recommended.

If the MFI is positive and the RPR is negative, the TP-PA is performed to resolve the discrepancy. Discrepant results can be seen in:

1) Patients with previously treated syphilis or latent infection. Historical and clinical evaluation required.

2) False Positive MFI3) Early primary syphilis in a person who has yet to develop nontreponemal

antibodiesPositive TP-PA results indicate past or present syphilis and the recommendations are identical to those described above. If the TP-PA is negative, syphilis is unlikely and as above, if recent infection is suspected, repeat testing in 4-6 weeks should be considered.

RPR+

Syphilis (Past or present)

Treponemal Ab EIA +

TP-PARPR-

Quantitative RPR or other

nontreponemal test

TP-PA -

Syphilis unlikely

TP-PA+

Syphilis (Past or present)

Treponemal Ab MFI -

Treponemal Ab MFI +

Treponemal Ab MFI

LimitationsNegative MFI and TP-PA results can be seen in immunocompromised patients. RPR on infant’s blood remains the primary screening test for congenital syphilis due to transplacental transfer of IgG antibodies detected by the MFI test in the newborn. Therefore, RPR testing on patients less than one year of age is recommended. An RPR level 4-fold higher than the mother indicates infection. The CSF-VDRL (avoid first tube) is recommended for diagnosis of neurosyphilis.

When making management decisions, clinicians should consider data other than the results of a serodiagnostic test alone. Data from a thorough physical examination, sexual and medical history should all be considered.

Specimen Requirements 1 mL serum – serum should be obtained by venipuncture, allowed to clot and the serum separated as soon as possible to prevent hemolysis. Samples may be stored at 2-8° for up to 7 days, or kept frozen at -20°C.

MethodMultiplex flow immunoassay (T. pallidum IgM & IgG / RPR)Passive particle agglutination (TP-PA)

Reference RangeNon-Reactive

Interpretative InformationSee above

Turnaround TimeSyphilis screens are run once daily. Reactive results are reflexed to the RPR test and any discrepancies will reflex to the new TP-PA. TP-PA test is run Monday, Wednesday, and Friday.

NoteRPR Titers (RPRQT) are performed on all reactive RPR samples. RPRQT should not be ordered. If therapeutic monitoring is needed please see test RPRMN.

CPT code*MFI- 86780RPR- 86592RPR Quant- 86593TP-PA- 86780

SOFT codeSYPHB

Result Interpretations

Treponemal Ab Nonreactive: Syphilis is unlikely. If recent infection is suspected, repeat testing in 4-6 weeks is recommended. False negative results may occur in severely immunocompromised patients.

Treponemal Ab Reactive, RPR Reactive: Consistent with past or present syphilis. Treatment is usually indicated unless the patient has been previously treated. Retreatment is indicated if the titer has increased by four fold or more.

Treponemal Ab Reactive, RPR Nonreactive, TP-PA Reactive: Consistent with past or present syphilis. Treatment is usually indicated unless the patient has been previously treated. Retreatment is indicated if the titer has increased by four fold or more.

Treponemal Ab Reactive, RPR Nonreactive, TP-PA Nonreactive: Syphilis is unlikely. If recent infection is suspected, repeat testing in 4-6 weeks is recommended. False negative results may occur in severely immunocompromised patients.

Treponemal Ab Reactive, RPR Nonreactive, TP-PA Indeterminate: Indeterminate testing obtained with TP-PA which is inconclusive in resolving the discordant RPR and MFI results. Repeat testing is recommended on a new specimen in a minimum of two weeks. Repeatedly inconclusive results should be tested with an alternative method i.e. FTA-ABS.

Treponemal Ab Equivocal, RPR Nonreactive, TP-PA Nonreactive: Syphilis is unlikely. If recent infection is suspected, repeat testing in 4-6 weeks is recommended. False negative results may occur in severely immunocompromised patients.

Treponemal Ab Equivocal, RPR Nonreactive, TP-PA Reactive: Equivocal MFI results obtained and subsequent nontreponemal and treponemal testing does not establish a diagnosis. Repeat testing is recommended on a new sample in two or more weeks.

Treponemal Ab Equivocal, RPR Nonreactive, TP-PA Indeterminate: Indeterminate results present. Recommend repeat testing on a new specimen after 2 weeks. Repeatedly inconclusive results should be confirmed by an alternative method (FTA-ABS)

Treponemal Ab Equivocal, RPR Reactive, TP-PA Nonreactive: Equivocal MFI results obtained and subsequent nontreponemal and treponemal testing do not establish a diagnosis. Repeat testing is recommended on a new sample in two or more weeks.

Treponemal Ab Equivocal, RPR Reactive, TP-PA Reactive: Consistent with past or present syphilis. Treatment is usually indicated unless the patient has been previously treated. Retreatment is indicated if the titer has increased by four fold or more.

Treponemal Ab Equivocal, RPR Reactive, TP-PA Indeterminate: Indeterminate results present. Recommend repeat testing on a new specimen after 2 weeks. Repeatedly inconclusive results should be confirmed by an alternative method (FTA-ABS)

*CPT codes provided are for informational purposes only. Questions regarding coding should be directed to the payor.

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