Test Name - Michigan



Syphilis Non-Treponemal Antibody Assay

(Unheated Serum Reagin – USR)

ANALYTES TESTED: Treponemal pallidum (syphilis) non-specific antibodies

USE OF TEST: A microscopic flocculation test to detect anti-lipoidal (cardiolipin, Reagin) antibodies in human serum for the serological diagnosis and prognosis of syphilis. The USR test is a nontreponemal assay similar to the RPR and the VDRL test. USR testing will be performed on all reactive or equivocal Syphilis Total IgG/IgM Multiplex Immunoassay (MIA) specimens or by special request.

SPECIMEN COLLECTION AND SUBMISSION GUIDELINES:

Test Request Form DCH-0583 

Specimen Submission Guidelines

Serum Specimen Collection DCH-0811

Transport Temperature: Frozen, wet ice or ambient temperature.

SPECIMEN TYPE:

Specimen Required: Serum

Minimum Acceptable Volume: 1 ml

Container: 3 ml polypropylene screw capped tube

Shipping Unit: Unit 8

SPECIMEN REJECTION CRITERIA:

Specimens lacking two unique patient identifiers (i.e., full name, date of birth) will not be tested.

Plasma, contaminated, chylous or grossly hemolysed specimens are unacceptable for testing and will be reported as Unsatisfactory.

TEST PERFORMED:

Methodology: Microflocculation

Turn Around Time: 7 days

Where/When Performed: Lansing/Tuesday, Thursday and Friday

RESULT INTERPRETATION:

Reference Range: NON-REACTIVE (no antibody detected)

1. Nonreactive Result:

No serologic evidence of current infection.

2. Reactive result:

Serologic evidence of current infection with a pathogenic treponeme or a biological false positive. Reactive serum will be titered to endpoint. The

endpoint titer is the highest serum dilution (i.e., 1:1, 1:2, 1:4) in which a reactive result is obtained. Most biological false positive reactions generally produce titers less than 1:16.

FEES: N/A

NOTES:

1. The USR test results must be interpreted according to the stage of syphilis suspected. In early primary syphilis, approximately 30% of the cases will have nonreactive USR results on initial visit. Nonreactive tests over a 3 month (1 week, 1 month, 3 months) period exclude the diagnosis of primary syphilis. In secondary syphilis, nearly all patients will have a positive USR titer greater than 1:16. Patients with atypical lesions and/or USR test titers below 1:16 should have a repeat USR test and a treponemal test performed. Approximately 20% of individuals with late latent syphilis will have nonreactive USR test results. A treponemal test should be performed in this situation.

3. A rising USR titer in serially obtained serum specimens from an infant over a 6 month period is diagnostic of congenital syphilis. By approximately 6 months, passively transferred antibodies should no longer be detected by the USR test.

4. Chronic false positive USR results may occur in cases of autoimmune disease (lupus, SLE, etc.), persons who abuse drugs, or in cases of other infections (e.g. leprosy, mononucleosis, malaria, viral pneumoniae, Lyme disease, etc).

5. Transitory false positives occur in 1-2% of pregnancies and up to 6 months after occurrence of various febrile diseases.

Interpretation Guide

|Non-Treponemal (USR)/Treponemal Test Result |Interpretation Guide |

|Nonreactive Treponemal (only) or |No serologic evidence of syphilis infection. |

|Nonreactive USR /Nonreactive Treponemal |Recommend additional testing consistent with clinical history findings*. |

|Reactive USR/Reactive Treponemal |Presumptive evidence of syphilis infection. |

|Nonreactive USR/Reactive Treponemal |Primary or latent infection, or previously treated or untreated syphilis. |

| |Recommend additional testing consistent with clinical history findings*. |

|Reactive USR/Nonreactive Treponemal |Syphilis infection unlikely; biological false positive likely. |

|(For special requests or forward algorithm testing) |Recommend additional testing consistent with clinical history findings*. |

|Reactive MIA Total (IgG/IgM)/Nonreactive USR/Indeterminate or |Primary or latent infection, or previously treated or untreated syphilis. |

|Atypical TP-PA (supplemental) |Recommend additional testing consistent with clinical history findings*. |

|Equivocal MIA Total (IgG/IgM)/Nonreactive or Reactive |Indeterminate for syphilis infection; potentially early infection or false positive. |

|USR/Indeterminate or Atypical TP-PA (supplemental) |Recommend additional testing consistent with clinical history findings*. |

|Equivocal or Reactive MIA Total (IgG/IgM)/ |No serologic evidence of syphilis infection. |

|Nonreactive USR/Nonreactive TP-PA (supplemental) |Recommend additional testing consistent with clinical history findings*. |

*Specimen may have been collected before the production of detectable antibody.

If recent infection is suspected, submit a convalescent specimen in 2-4 weeks (or one week if patient is pregnant).

The predictive value of a reactive USR test in the serologic diagnosis of syphilis is increased when combined with a

reactive treponemal test. Interpretation of results must be used in conjunction with the clinical signs and symptoms,

medical history and other clinical/laboratory findings.

ALIASES: USR, Nontreponemal assay, Reagin antibody

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