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Validation of commercial kits for detection of antibodies to Legionella

Abstract number: p990

Elverdal  P., Uldum  S.A.

Objectives: 

Validation of four commercial kits for detection of antibodies to Legionella (L.) pneumophila by comparison with an in-house Legionella IFA assay. Three-kits were indirect Enzyme-Linked Immunosorbent Assays (ELISA) and one kit was an indirect immunofluorescent antibody assay (IFA). For this study, the kits were tested with sera, which had been tested positive for other bacteria than Legionella, and with in-house IFA assay positive sera from patients with L. pneumophila infection.

Methods: 

Seventy-five sera, which had been tested positive for other bacteria (Campylobacter, Helicobacter, Riskettsia, Mycoplasma pneumonia, Chlamydia group, Pseudomonas aeruginosa and Coxiella) than Legionella. One hundred in-house IFA assay positive sera (titre >= 256) from patients with L. pneumophila infection confirmed by one of the following methods: PCR, culture or Legionella urinary antigen test. In the in-house IFA assay heat inactivated L. pneumophila serogroup 16, L. micdadei and L. bozemanii were used as antigens. The kits, which were validated, were: (i) Focus Diagnostics IFA kit for L. pneumophila serogroup 1–6 and 8, (ii) SERION ELISA classic for L. pneumophila 1–7 IgM kit, (iii) SERION ELISA classic for L. pneumophila 1–7 IgG kit, and (iv) Zeus Scientific, Inc. L. pneumophila serogroup 1–6 ELISA kit

Results: 

In Table 1, it can be seen that the sensitivity was highest for the Focus Diagnostics kit (77%), but this kit also had the next highest false positive rate properly caused by cross-reaction (16%). To compare the SERION ELISA classic kits with the other kits, the IgM and IgG results were combined because the other kits all detect IgG/IgM/IgA. The SERION ELISA classic kits had a sensitivity of 73.9% and a false positive rate of 5.6%, when the two kits (IgM + IgG) results were combined. Table 1: Numerical percent of sensitivity and cross-reaction in kits and LAT.

Conclusion: 

The Focus Diagnostics, SERION ELISA classic and Zeus Scientific, Inc. ELISA kits are all relatively sensitive. But both Focus Diagnostics and Zeus Scientific, Inc. ELISA kits have high false positive rates. The best kit, compared to the in-house assay, is the SERION ELISA classic kit when the IgM and IgG results are combined, because it has the best combination of a relative high sensitivity and a low false positive rate.

Session Details

Date: 01/08/2007
Time: 00:00-00:00
Session name: XXIst ISTH Congress
Subject:
Location: Oxford, UK
Presentation type:
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