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Kim, Kim, Cho, Kim, Kim, Nam, Kim, Bae, and Cho: Evaluation of Automated Architect Syphilis TP as a Diagnostic Laboratory Screening Test for Syphilis
Original Article

Korean J Leg Med 2008;28(6):475-482.

Published online: 14 February 2008

DOI: https://doi.org/10.3343/kjlm.2008.28.6.475

Evaluation of Automated Architect Syphilis TP as a Diagnostic Laboratory Screening Test for Syphilis

Jeeyong Kim, M.D., Woo-Hyeun Kim, M.D., Chihyun Cho, M.D., Juyeon Kim, M.D., Ga-Yeong Kim, M.D., Myung-Hyun Nam, M.D., Jang Su Kim, M.D., Sook Young Bae, M.D., Yunjung Cho, M.D.

Department of Laboratory Medicine, Korea University Hospital, Seoul, Korea

Corresponding author: Yunjung Cho, M.D. Department of Laboratory Medicine, Korea University Hospital, 126-1 Anamdong 5-ga, Seongbuk-gu, Seoul 136-705, Korea Tel: +82-2-920-5612, Fax: +82-2-920-5538 E-mail: eqcho1ku@korea.ac.kr

Received 24 October 200831 October 2008       Accepted 31 October 2008

Copyright © 2008 by the Korean Society for Legal Medicine

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background

The aim of the study was to establish a new syphilis test algorithm using Architect Syphilis TP (Abbott Japan, Japan: AST), a fully automated treponemal antibody test, as a screening test in a university hospital laboratory. We evaluated performance characteristics of AST in various patient groups.

Methods

A total of 1,357 serum samples obtained from patients at a university hospital from June to August, 2008 were categorized into checkup, preoperative, other diseases, diagnosis (clinically suspected of syphilis), and follow up groups. We compared the results of AST with those of RPR (N=1,276) or Treponema pallidum hemagglutination assay (TPHA, N=81). Samples with discrepant results between RPR or TPHA and AST were retested by fluorescent treponemal antibody absorption test (FTA-ABS) and all patients’ clinical records were thoroughly reviewed.

Results

The positive rate of AST was significantly higher than that of RPR in preoperative and other diseases groups and was the same as that of RPR in diagnosis group. There were no significant differences in check up and follow up groups. The results of AST showed 97.4% (1,243/1,276) and 97.5% (79/81) concordance rates with those of RPR and TPHA, respectively. Among 26 RPR-AST discrepant and FTA-ABS confirmed cases, there were 20 RPR false-negatives, 4 RPR false-positives, 1 AST false-negative, and 1 AST false-positive.

Conclusions

Based on the results and literature review, we established a new syphilis test algorithm using AST as a screening test, which would be helpful for detection of more syphilis patients including latent infections.

Keywords: Architect Syphilis TP, Automated syphilis test, RPR, TPHA

REFERENCES

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Fig. 1.
Quantitative correlation plot between TPHA titer and Architect Syphilis TP S/CO. R=0.802 (P<0.001).
kjlm-28-475f1.tif

Abbreviations: TPHA, Treponema pallidum hemagglutination assay; S/CO, signal to cut-off ratio.

Fig. 2.
Syphilis testing algorithm using Architect Syphilis TP for initial screening.
kjlm-28-475f2.tif

∗, The patients who are clinically suspicious of syphilis or other sexually transmitted diseases.

Table 1.
Age distribution of patients with requests for RPR
Group∗ Male Female
N (692) Median Range N (584) Median Range
Check up 182 46 17-79 150 46 25-78
Pre-op 239 47 6-88 208 50 5-87
Other diseases 263 48 2-85 211 43 3-87
Diagnosis 3 53 18-73 12 40 19-73
Follow-up 5 34 24-51 3 38 35-38

∗ , Check up, visitors for health check up; Pre-op, patients for preoperative screening test; Other disease, patients with various diseases to rule out syphilis; Diagnosis, patients who are highly suspicious of syphilis; Follow up, confirmed syphilis patients with follow-up. Abbreviations: N, number; RPR, rapid plasma reagin.

Table 2.
Number and percentage for reactive results in each group by RPR and Architect Syphilis TP (AST)
Group∗ Total N (%) of RPR reactive N (%) of AST reactive P†
Check up 332 1 (0.3) 5 (1.5) 0.125
Pre-op 447 5 (1.1) 15 (3.4) 0.021
Other diseases 474 19 (4.0) 27 (5.7) 0.039
Diagnosis 15 8 (53.3) 8 (53.3) 1.000
Follow up 8 8 (100) 7 (87.5)  
Total 1,276 41 (3.2) 62 (4.8) 0.000

∗ , See Table 1;

† , McNemar Test.

Abbreviations: See Table 1

Table 3.
Comparison of RPR and Architect Syphilis TP results
RPR Architect Syphilis TP Total
Reactive Non-reactive
Reactive 35 6 41
Non-reactive 27 1,208 1,235
Total 62 1,214 1,276

Abbreviation: RPR, rapid plasma reagin.

Table 4.
Comparison of TPHA and Architect Syphilis TP results
TPHA Architect Syphilis TP Total
Reactive Non-reactive
Reactive 24 0 24
Non-reactive 2∗ 55 57
Total 26 55 81

∗ , The results of FTA-ABS were positive and their clinical diagnoses were bladder tumor and lung destruction due to tuberculosis, respectively.

Abbreviation: TPHA, Treponema pallidum hemagglutination assay.

Table 5.
Clinical diagnosis of the cases with discrepant results between RPR and Architect syphilis TP
Decision Group∗ N STS† Clinical diagnosis
RPR false negative (20) Check up 4 NRRN Flat adenoma of stomach; eosinophilia; healthy status; benign prostatic hyperplasia
  Pre-op 10 NRRN Carpal tunnel syndrome; burst fracture of T12; compression fracture of T12; osteoarthritis of both knees; septic bursitis; avascular necrosis of femoral head; sigmoid colon cancer; right shoulder rotator cuff tear; fibrous dysplasia of right lower limb; coronary artery occlusive disease
  Other diseases 5 NRRN Concussion with periorbital contusion; brain & lung abscess; prostate cancer; conjunctivitis; acute HIV infection syndrome
    1 NRRR Recurrent oral aphthae
RPR false positive (4) Pre-op 2 RNNN Hyphema; impacted teeth
  Other diseases 2 RNNN Normal pregnancy; glaucoma
AST false negative (1) Follow up 1 RNRR Primary syphilis‡
AST false positive (1) Other diseases 1 NRNN Angioedema§
Pending (7) Pre-op 4 NRXX Prostate cancer; adenomyosis; impacted teeth; intraheptic duct stone
    1 RNXX Cervical spondylosis
  Other diseases 2 NRXX Chronic renal failure; condyloma accuminatum

∗ , See Table 1;

† , Results of RPR, AST, FTA-ABS IgG, and FTA-ABS IgM in order;

‡ , Syphilis patient with genital ulcers;

§ , Angioedema patient without any symptoms of syphilis.

Abbreviations: STS, serologic tests for syphilis; N, nonreactive; R, reactive; X, not done; RPR, rapid plasma reagin; AST, Architect Syphilis TP.

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