Estimate herd test characteristics when pooled sampling is used
We may wish to designate a group of individuals (e.g. a herd) as being either diseased or non-diseased on the basis of pooled samples. This function estimates sensitivity and specificity of this testing regime at the group (or herd) level.
epi.pooled(se, sp, P, m, r)
se |
a vector of length one defining the sensitivity of the individual test used. |
sp |
a vector of length one defining the specificity of the individual test used. |
P |
scalar, defining the estimated true prevalence. |
m |
scalar, defining the number of individual samples to make up a pooled sample. |
r |
scalar, defining the number of pooled samples per group (or herd). |
A list containing the following:
HAPneg |
the apparent prevalence in a disease negative herd. |
HSe |
the estimated group (herd) level sensitivity. |
HSp |
the estimated group (herd) level specificity. |
Dohoo I, Martin W, Stryhn H (2003). Veterinary Epidemiologic Research. AVC Inc, Charlottetown, Prince Edward Island, Canada, pp. 115 - 117 .
Christensen J, Gardner IA (2000). Herd-level interpretation of test results for epidemiologic studies of animal diseases. Preventive Veterinary Medicine 45: 83 - 106.
## We want to test dairy herds for Johne's disease using faecal culture ## which has a sensitivity and specificity of 0.647 and 0.981, respectively. ## Suppose we pool faecal samples from five cows together and use six pooled ## samples per herd. What is the herd level sensitivity and specificity ## based on this approach (assuming homogenous mixing)? epi.pooled(se = 0.647, sp = 0.981, P = 0.12, m = 5 , r = 6) ## Herd level sensitivity is 0.927, herd level specificity is 0.562. ## Sensitivity at the herd level is increased using the pooled sampling ## approach; herd level specificity is decreased.
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