TABLE 6.

Post-test probabilities of M. paratuberculosis infection for ELISA B at five levels of assay result and within-herd M. paratuberculosis infection prevalence ranging from 1 to 30%a

ELISA resultLRbWithin-herd true prevalence (pretest infection probability) (%) at:
5%10%15%20%25%30%
<0.000.482.55.17.810.713.817.1
0.00-0.0501.547.514.621.427.833.939.8
0.051-0.1002.8413.023.933.341.448.554.8
0.101-0.50054.2474.185.890.593.194.895.9
≥0.500c91.395.797.298.098.598.8
  • a The calculation steps were as follows: (i) pretest odds = (pretest probability)/[1 − (pretest probability)]; (ii) post-test odds = pretest odds × LR; and (iii) post-test probability = (post-test odds)/(post-test odds + 1).

  • b LR for ELISA B from Table 5.

  • c A value of 200 was used instead of dividing by ∞.