This indicates the statistical probability of arriving at the correct test result when using more than one testing kit. This highlights the need to carefully select the test kit that fits your needs and fits into the processors testing scheme that will give you the maximum chance of arriving at correct results. Other considerations are testing time and cost. Kits that are faster are generally antibody-based and require very careful attention to the instructions, especially the incubation temperature. Dr. Cullor's data raises may questions concerning antibiotic testing for individual cows because he used cows with mastitis to evaluate commercial kits, but the kits were developed using normal bulk milk spiked with antibiotics.
Tests done on milk from bulk storage tanks are much more likely to arrive at the correct result.
Data from individual cows cannot be extrapolated to bulk milk data. Antibiotic testing is more accurate in bulk tanks because the milk has been comingled, which dilutes any of the natural antibiotics normally found in animals with subclinical or clinical mastitis. Most Utah processors use a multilevel evaluation testing scheme when testing bulk tankers for antibiotics to reduce false results. For example, the processor may screen each load with a rapid test. If the screening test is positive, a different test is done to check or confirm the results of the rapid screening test.