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Comparison of ELISA and CFT assays for Chlamydophila abortus antibodies in ovine sera
Author(s) -
McCauley LME,
Lancaster MJ,
Young P,
Butler KL,
Ainsworth CGV
Publication year - 2007
Publication title -
australian veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.382
H-Index - 59
eISSN - 1751-0813
pISSN - 0005-0423
DOI - 10.1111/j.1751-0813.2007.00189.x
Subject(s) - chlamydophila , antibody , virology , biology , immunology , chlamydia
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.