Literature reviews  >  Articles for review > Hagedorn et al. Evaluation of INNO-LIA... 

Evaluation of INNO-LIA Syphilis assay as a confirmatory test for syphilis.
Hagedorn H-J, Kraminer-Hagedorn A, De Bosschere K, Hulstaert F, Pottel H, Zrein M.  
Journal of Clinical Microbiology 2002;40:973-978.

Summary:

Question
What is the sensitivity and specificity of the INNO-LIA Syphilis test for the detection of treponemal antibodies?

Design
Single-blinded, cross-sectional retrospective comparison of the multiparameter line-immunoassay INNO-LIA with a consensus diagnosis of syphilis based on conventional serological assays. All samples were tested by TPHA,VDRL, and IgG-FTA-ABS. Some samples were additionally tested by 19S-IgM-FTA-ABS, IgM EIA, and immunoblotting.

Participants
289 negative, 219 positive and 23 indeterminate sera samples (based on a consensus diagnosis of syphilis derived from conventional serology) from patients in one of 4 groups: 1) 43 Russian blood donors, 2) 195 THPA reactive (titer > 1:80), 3) 203 pregnant women, and 4) 90 patients with one of 13 inflammatory or infectious diseases.

Description of Tests and Diagnostic Standard
Serum samples were tested with conventional syphilis serology tests according to the manufacturers' instructions: 1) TPHA (Serokit LD, Innogenetics GmbH, Heiden, Germany) at a serum dilution of 1:80. 2) FTA-ABS using the T. pallidum antigen and the T. phagedenis ultrasonicate (Ultrasorb, BAG, Lich, Germany) and an IgG-specific anti-human fluorescein isothiocyanate-conjugated antibody (Gull Laboratories, Bad Hamburg, Germany) at serum dilutions of 1:5 and 1:20, and 3) VDRL (VDRL-Cardiolipin-Antigen, Behringwerke AG, Marburg, Germany), 4) 19S-IgM-FTA-ABS using slides coated with treponemal organisms (FTA-ABS slides, Innogenetics) and an IgM-specific anti-human antibody (Gull Laboratories) after incubation overnight with anti-IgG serum (GullSORB, Gull Laboratories) and diluted with T. phagedenis ultrasonicate (Ultrasorb, BAG) to a final dilution of 1:10, 5) IgM EIA (Captia M-Syphilis EIA, Gull Laboratories), and 6) T. pallidum immunoblotting (MarDx, Carlsbad, CA). Based on a consensus diagnosis derived from these serological tests, all of the sera were classified as positive, negative, or indeterminate and the results were compared to those of the INNO-LIA Syphilis assay, a multiparameter line immunoassay for detection of antitreponemal antibodies using recombinant and synthetic peptides from T. pallidum membrane proteins. Control lines are provided for semiquantitative evaluation, verification of sample addition, and negative control samples. Samples were diluted 1:100 and incubated overnight.

Main Outcome Measures
The sensitivity and specificity of the INNO-LIA asssay for the detection of syphilis as determined by consensus results of conventional serological testing.

Main Results
Sensitivity and specificity were calculated in relation to the consensus determined by the investigator (table). For the clear-cut positive (n = 219) or negative (n = 289) samples, the sensitivity of the INNO-LIA Syphilis was 100% and the specificity was 99.3%. One sample was invalid due to cross-reactive antibodies. Compared to TPHA and IgG-FTA-ABS, the INNO-LIA gave a significantly higher number (P = 0.021 and P < 0.0001, respectively) of correct results than either of these other two tests.

Authors' Conclusions
The INNO-LIA can be considered a valid alternative to the FTA-ABS test for the confirmation of syphilis screening results, and its use can improve the reliability of syphilis serology.

Source of funding: None given

For correspondence: Maan Zrein, Innogenetics NV, Technologiepark 6, B-9052 Ghent, Belgium. E-mail address: mann_zrein@innogenetics.com.

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