3.2 Analysis of pooled specimens
Pooling of specimens involves combining aliquots of individual specimens and testing the pooled sample. If the pool is negative, all the specimens are considered negative. If the pool is positive and one needs to know the status of each individual specimen, each specimen must be collected separately and then be tested separately. Specimens can be pooled from a single subject, for example, four milk specimens taken from four quarters of the same cow or from different animals.
What are the advantages of pooling specimens?
Answer
Advantages of specimen pooling can include:
- reduced cost (test all for the price of one)
- increased farm-level testing sensitivity when it is uneconomical to test each animal separately
- detection of multiple pathogens (co-infections) at the farm level, without the need to test all the specimens for all the pathogens.
The disadvantage of pooling is that the number of bacteria in each combined specimen is diluted. Thus, if the bacterial load is small, the bacterial numbers may fall below the LoD of culture. Hence, the decision on pooling must be taken on a case-by-case basis considering the dilution effect.
3.1 Analysis of multiple specimens
