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Analysis of 3 algorithms for syphilis serodiagnosis and implications for clinical management
Man-Li Tong1, Li-Rong Lin, Li-Li Liu
1Zhongshan Hospital, Medical College of Xiamen University.
Insights
The European Centre for Disease Prevention and Control (ECDC) algorithm offers superior syphilis diagnosis accuracy compared to traditional methods. This treponemal-based approach is recommended for high-prevalence populations.
Area of Science:
- Infectious Disease Epidemiology
- Clinical Diagnostics
- Microbiology
Background:
- Syphilis diagnostic algorithms are controversial and complex for clinicians.
- Accurate and efficient syphilis testing is crucial for public health.
- Existing diagnostic approaches present interpretation challenges.
Purpose of the Study:
- To compare the diagnostic accuracy of three syphilis testing algorithms: traditional, reverse, and ECDC.
- To evaluate the concordance between the reverse and ECDC algorithms.
- To determine the optimal algorithm for syphilis diagnosis in a large cohort.
Main Methods:
- A cross-sectional study involving 24,124 subjects.
- Simultaneous evaluation of serum samples using rapid plasma reagin, Treponema pallidum particle agglutination, and chemiluminescence immunoassay.
- Comparison of algorithm performance against clinical syphilis diagnoses as the gold standard.
Main Results:
- The traditional algorithm demonstrated low sensitivity (75.81%) and a high missed diagnosis rate (24.2%).
- The reverse and ECDC algorithms exhibited significantly higher diagnostic efficacy, with sensitivity, specificity, and accuracy ranging from 99.38% to 100.00%.
- High concordance (99.9% agreement, κ=0.996) was observed between the reverse and ECDC algorithms.
Conclusions:
- The ECDC algorithm, starting with a treponemal immunoassay followed by a second treponemal assay, is supported for syphilis screening in high-prevalence settings.
- Nontreponemal assays are deemed unnecessary for initial syphilis diagnosis but useful for monitoring serological activity and treatment response.
- The study advocates for adopting more accurate treponemal-based algorithms for improved syphilis detection.
Background:
Algorithms for the diagnosis of syphilis continue to be a source of great controversy, and numerous test interpretations have perplexed many clinicians.
Methods:
We conducted a cross-sectional study of 24 124 subjects to analyze 3 syphilis testing algorithms: traditional algorithm, reverse algorithm, and the European Centre for Disease Prevention and Control (ECDC) algorithm. Every serum sample was simultaneously evaluated using the rapid plasma reagin, Treponema pallidum particle agglutination, and chemiluminescence immunoassay tests. With the results of clinical diagnoses of syphilis as a gold standard, we evaluated the diagnostic accuracy of the 3 syphilis testing algorithms. The κ coefficient was used to compare the concordance between the reverse algorithm and the ECDC algorithm.
Results:
Overall, 2749 patients in our cohort were diagnosed with syphilis. The traditional algorithm had the highest negative likelihood ratio (0.24), a missed diagnosis rate of 24.2%, and only 75.81% sensitivity. However, both the reverse and ECDC algorithms had higher diagnostic efficacy than the traditional algorithm. Their sensitivity, specificity, and accuracy were 99.38%-99.85%, 99.98%-100.00%, and 99.93%-99.96%, respectively. Moreover, the overall percentage of agreement and κ value between the reverse and the ECDC algorithms were 99.9% and 0.996, respectively.
Conclusions:
Our research supported use of the ECDC algorithm, in which syphilis screening begins with a treponemal immunoassay that is followed by a second, different treponemal assay as a confirmatory test in high-prevalence populations. In addition, our results indicated that nontreponemal assay is unnecessary for syphilis diagnosis but can be recommended for determining serological activity and the effect of syphilis treatment.
