IngentaConnect Comparison of ELISA and CFT assays for Chlamydophila abortus anti...

Abstract:

Objective

To compare the sensitivity and specificity of Chlamydophila abortus antibody assays, to find a suitable serological assay for testing sheep for export. Design

Comparison of results from known positive and negative sheep populations. Procedure

Fifty-five positive and fifty negative sera were analysed by four enzyme linked immunosorbent assays (ELISA), three using recombinant antigens based on the chlamydial polymorphic outer membrane proteins (POMP90-3, POMP90-4, POMP80-90) and one using a synthetic peptide based on chlamydial major outer membrane proteins (MOMP-P). They were also analysed by complement fixation tests (CFT) using crude antigens from chlamydia isolated from an Australian sheep, a Californian parakeet and a Texan turkey. Assay sensitivity and specificity were expressed as point estimates and 95% confidence intervals. Results were compared using McNemar's test for paired samples. Results

ELISA sensitivity ranged from 70 to 98% and complement fixation test sensitivity from 60 to 96%; with POMP90-3 > POMP90-4 > CFT (parakeet) > CFT (turkey) > POMP80-90 > MOMP-P > CFT (sheep). There was no significant difference from POMP90-3 to POMP80-90 (P > 0.05). ELISA specificity ranged from 88 to 100% and CFT specificity was 100% for all three antigens; with CFT and POMP90-4 > MOMP-P > POMP80-90 > POMP90-3. There was no significant difference from CFT to POMP80-90 (P > 0.05). Changing the CFT cut-off from 1:32 to 1:4 substantially reduced the specificity with little improvement in sensitivity. Conclusion

Assays using POMP90-4, POMP80-90, CFT (parakeet) and CFT (turkey) had equivalent sensitivity and specificity; none of the ELISAs were more specific than any CFT. The POMP80-90 ELISA is recommended as an alternative to CFT (parakeet) but as its specificity is not ideal the search for a more specific assay should continue.

Aust Vet J 2007;85:325-328

doi: 10.1111/j.1751-0813.2007.00189.x

Keywords: Chlamydophila abortus; sensitivity; specificity; complement fixation; ELISA; sheep

Document Type: Research article

DOI: 10.1111/j.1751-0813.2007.00189.x

Affiliations: 1: Primary Industries Research Victoria, Department of Primary Industries, Attwood VIC 3049;, Email: Lisette.McCauley@dpi.vic.gov.au 2: Primary Industries Research Victoria, Department of Primary Industries, Werribee VIC 3030

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Comparison of ELISA and CFT assays for Chlamydophila abortus antibodies in ovine sera