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Test ID: RPR Test
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Rapid Plasma Reagin test
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Non-treponemal qualitative and semi-quantitative testing procedure for serologic detection of syphilis in patient serum
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Useful For
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Rapid Plasma Reagin (RPR) is a non-treponemal flocculation test that can qualitatively determine the presence of reagin antibodies against tissue-derived lipid components, namely cardiolipin, lecithin and cholesterol in human serum.
Serologic testing for syphilis consists of an algorithm approach. The traditional algorithm is to screen with a non-treponemal assay and then confirm with a treponemal assay which detects antibodies that are specific to Treponema pallidum (T. pallidum). The reverse algorithm involves using a treponemal assay followed by a non-treponemal test.
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Method name and description
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Specimen type / Specimen volume / Specimen container
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Specimen type: Serum
Specimen volume: 3-5 mL
Specimen container: Serum collected in Yellow top gel tube
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Collection instructions / Special Precautions / Timing of collection
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Collection by venipuncture as per organization guidelines
No special precautions/ No timing of collection
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Storage and transport instructions
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Maintain specimen at 2-8°C
The specimens should be transported to Virology Section in cold box immediately
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Specimen Rejection Criteria
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Quantity of blood not sufficient
Wrong blood container
Container breakage / sample leaking
Lipemic sample
Grossly hemolyzed serum
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Biological reference intervals and clinical decision values
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Non-Reactive: Indicates that the sample tested either does not contain RPR antibodies or that it contains RPR antibodies at concentrations below the detectable limits.
Reactive: Indicates that the sample tested contains RPR antibodies
Reactive with titer (e.g. 1:2; 1:4; 1:8; 1:16; 1:32; 1:64; 1:128; 1:256): Indicates the highest dilution that showed a reactive result.
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Factors affecting test performance and result interpretation
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- Results should always be interpreted in conjunction with additional treponemal serologic test results, the patient’s clinical symptoms, medical history, and other clinical and/or laboratory findings to produce a diagnosis of syphilis by disease stage.
- A reactive test result is not diagnostic of syphilis without additional serologic testing and a full clinical evaluation.
- Results in samples from immunosuppressed patients or from patients with disorders leading to immunosuppression should be interpreted with caution.
- Specimens with reactive non-treponemal results should be further tested by serial dilution endpoint titration to establish a base line from which changes in titer can be determined.
- Reactive non-treponemal test results should be followed up with treponemal antibody testing.
- Biological false reactive results have been reported in diseases or conditions such as infectious mononucleosis, pregnancy, leprosy, malaria, intravenous drug users, autoimmune disease, lupus erythematosus, vaccinia, viral pneumonia, and in people who have been recently immunized.
- Pinta, yaws, bejel and other treponemal diseases may produce reactive results with non-treponemal tests.
- A prozone effect may occur in samples with high antibody concentrations, causing weak or false-negative results. If suspected, the sample should be retested using serial dilutions (titration).
- Following treatment, non-treponemal antibody titers in patients with latent or late-stage syphilis, or those with reinfection, may decline more slowly than in patients with early primary infection. Some individuals may remain serofast, with persistent low-level reactive titers for life.
- Sample degradation, heating, turbidity, hemolysis, debris, or contamination may lead to false test results.
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Turnaround time / Days and times test performed / Specimen retention time
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Turnaround time: Within 7 calendar days
Days and times test performed: 3 times a week
Specimen retention time: 2 weeks
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