Improved reverse screening algorithm for Treponema pallidum antibody using signal-to-cutoff ratios from chemiluminescence microparticle immunoassay.

Abstract

BACKGROUND:

The widespread reverse syphilis screening algorithm involves 1 more treponemal test than the traditional screening algorithm, resulting in increased medical costs. In the first screening step of the algorithm, a chemiluminescence microparticle immunoassay is used to detect Treponema pallidum (TP) antibody on the basis of signal-to-cutoff (S/CO) ratios. We hypothesized that by analyzing S/CO ratios, we could determine a strategy to reduce unnecessary confirmatory testing.

METHODS:

The ARCHITECT Syphilis TP assay using the chemiluminescence microparticle immunoassay was used as a syphilis screening test, and all reactive results were followed up with a toluidine red unheated serum test (TRUST) and a TP particle agglutination (TPPA) assay. We evaluated the S/CO ratios of 319 reactive samples of a total of 8980 that were included in the screening tests. A receiver operating characteristic curve was used to determine the optimal S/CO ratio to predict confirmatory TPPA results.

RESULTS:

When the S/CO ratio was 9.9 or greater, the specificity and positive predictive value were both determined to be 100.0%. All samples (194/194) with S/CO ratios of 9.9 or greater, even with negative results for TRUST, were confirmed to be positive for treponemal antibody.

CONCLUSIONS:

A sample with an S/CO ratio of 9.9 or greater in initial screening does not need an extra confirmatory TPPA test, although the sample has a negative result for TRUST. We propose a potentially cost-effective reverse screening algorithm, obviating the need for the secondary treponemal testing in 65.2% of the screening-reactive samples.

• Authors: Shuqin Dai, Peidong Chi, Yuehao Lin, Xin Zheng, Wen Liu, Jingping Zhang, Qiuyao Zeng, Xingping Wu, Wanli Liu, Junye Wang
• Journal: Sexually transmitted diseases (Sex Transm Dis) Vol. 41 Issue 1 Pg. 29-34 (Jan 2014) ISSN: 1537-4521 [Electronic] United States
• PMID: 24326578 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antibodies, Bacterial

Topics

• Algorithms
• Antibodies, Bacterial (isolation & purification)
• Female
• Humans
• Immunoenzyme Techniques
• Luminescent Measurements
• Male
• Mass Screening (methods)
• Sensitivity and Specificity
• Syphilis (diagnosis, immunology)
• Treponema pallidum (immunology, isolation & purification)