Part 2 of a 2-part series: Navigating Syphilis Diagnostic Changes

May 2020 - Vol. 9 No. 5 - Page #6

Visit for Part 1 of this series.

In the April issue of MedicalLab Management, part 1 of this 2-part series detailed CPL’s transition to a rapid plasma reagin (RPR), assay-based automated test system for syphilis testing. This first part included information on methodology change, clinical overview, evolving screening recommendations, and the laboratory’s management of testing algorithms. Here in part 2, we discuss the automation initiative, analytical process monitoring, and overall management considerations.

Automation Initiative and TP-PA Implementation

Our recent transition from the manual to automated RPR method was met with a period of skepticism and uncertainty as we were presented with a number of questions regarding sensitivity and specificity. A majority of clients expected a continued level of test performance regardless of methodology. Others have found the false-positive RPR rate for the automated system to be up to 44% during direct correlation, but also identified true RPR positive specimens contrary to the manual card method.1

Shortly after our transition to the automated RPR screening platform, a communication was crafted to clinicians that included a message code for weakly reactive RPR-positive specimens. The learning curve was quite prevalent with various clinicians and clients, considering increased sensitivity (1.6 to 2.7% positivity rate) and decreased specificity resulting in a lower positive predictive value (58% to 42%). Approximately 57% of the borderline RPR positive cases did not confirm positive by TP-PA compared to 29% previously (see FIGURES 2 & 3). Our consistent message throughout was that the FDA continues to recommend a confirmatory treponemal test for diagnosis of syphilis; RPR reactive results alone are not sufficient.2

For follow up on patients screening RPR positive, TP-PA testing is needed. The increased sensitivity of our automated RPR assay contributed to an increase in TP-PA volume performed by the hematology department. This volume was also supplemented by implementation of TP-PA reflex testing for designated obstetric panels.

Regardless of the preferred screening algorithm, discriminating between latent syphilis infection and a false-positive screening test can be challenging for patients without a clear history. The CDC recommends testing these samples with a second treponemal assay.2 Our current confirmatory methodology detects total antibodies from previous and current infections (see FIGURE 1).

Analytical Process Monitoring

Our laboratory developed a quality management (QM) program around the insourcing of TP-PA testing in order to closely monitor the reporting of inconclusive results. Inconclusive reporting for TP-PA requires a comment recommending additional testing. Beginning in July 2019, a total of six technologists participated in the QM study, with one tech performing the initial TP-PA analysis and a second tech performing the repeat TP-PA, if necessary. This correlation data is tracked monthly at the accession level in order to better understand and evaluate inconsistencies with inter-tech performance.

This QM program also has allowed our laboratory to establish a baseline from which to expand and refine our confirmatory testing for inconclusive results. Inconclusive specimen confirmations were initially reported as such. After several months of analysis and consultation with the medical directors and review of the package insert, a revised flow chart was implemented that relied on the documented sensitivity of the TP-PA test. For TP-PA specimens testing as inconclusive twice in a row, the treponema total antibody procedure is used for generation of a final report comment. This process is likely to be modified and adjusted with industry recommendations (see FIGURE 4).

Overall Management Considerations

Our transition from manual flocculation cards to the automated instrument methodology required some additional research and analysis to cater to client needs and expectations. However, it has been a successful move that has improved our operations. Implementing the manual TP-PA confirmatory test has provided our medical leadership and staff a better grasp of clinical implications at various points during disease progression.

Overall, several recommendations can be distilled from our experiences with automated RPR testing and insourcing confirmatory testing in order to facilitate a successful transition:

  • Research industry trends that can be used to align current testing and client focus
  • Form a strong partnership with the vendor in order to properly anticipate and effectively respond to client concerns as they arise
  • Educate clients/clinicians on the benefits of the new technology but listen to all concerns
  • Understand and communicate to stakeholders that clinical recommendations may negatively impact the financial bottom line
  • Utilize analytic tools in order to build consistency and identify trends that could shed light on underlying issues
  • Develop tight monitoring criteria to evaluate new/revised processes with multiple factors

Special thanks to Mr. Michael Callaway, Director of Technical Operations; Dr. Mark Silberman, Laboratory Director; Dr. Kim Monnin, Hematology Medical Director; and Dr. Christine Burgess, Chemistry Medical Director; Clinical Pathology Laboratories, Austin, TX.


  1. Sanfilippo AM, Freeman K, Schmitz JL. Comparison of Manual and Fully Automated AIX1000 Rapid Plasma Reagin Assays for Laboratory Diagnosis of Syphilis. J Clin Microbiol. 2018;56(8).
  2. CDC. 2015 Sexually Transmitted Diseases Treatment Guidelines. Accessed 3.20.20.

Aaron Samson, MBA, MB(ASCP)CM, is the hematology operations manager at CPL in Austin, Texas, where he oversees staff in various areas of specimen testing. Prior to joining CPL in 2012, Aaron performed high complexity flow cytometry and molecular testing at the University of Kentucky Medical Center. He has experience with lab automation implementations, project management, and process improvement.


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