2.8. Diagnostic sensitivity, specificity and accuracy
The test results were analysed for the sensitivity, specificity
and percentage of agreement by using kappa statistics (Kelsey
et al., 1986). The diagnostic sensitivity, specificity and accuracy
of the single dilution ELISA for the detection of FAdV-4
antibodies were determined in comparison to the Q-AGID. Sensitivity
= a/(a + c) × 100 where ‘a’ is the number of sera positive by
single dilution ELISA and Q-AGID, ‘c’ is the number of sera positive
by Q-AGID but negative by ELISA. Specificity = d/(b + d) × 100
where ‘d’ is the number of sera negative by single dilution ELISA
and Q-AGID, ‘b’ is the number of sera negative by Q-AGID but positive
by recombinant antigen ELISA. Accuracy is calculated using
the formula, (a + d)/(a + b + c + d) × 100. The results obtained from
the tests were analysed for the percentage of agreement by kappa
statistics: k = (a + d − P)/(1 − P) where P = (a + b)(a + c) + (c + d)(b + d).
A kappa value greater than 0.81 indicates perfect agreement.