There are typically two sources of sample carryover (from one cow to the next) in a routine milk recording or herd testing operation: Milk meter carryover on-farm Sample needle carryover at the milk testing laboratory Both carryover sources present the possibility of pathogens in the first sample being transferred (or ‘carried over’) into the sample of the next animal. For direct pathogen detection methods such as microbial culture or PCR (where specific bacterial DNA are amplified and detected), this presents an opportunity for false-positive results. The StaphGold ELISA test procedure involves a ten-fold dilution step during sample preparation. Should milk from a cow with high antibody levels be carried over, the subsequent sample will first be greatly diluted (approximately 100-fold) by the next milk sample, then diluted ten-fold during test sample preparation. Any remaining antibodies will therefore come in well under the limit of detection and thus generate a ‘Negative’ ELISA result for S. aureus. If the second animal has a somatic cell count below 250,000/mL, it would not be a candidate for StaphGold ELISA testing, in any case. NB: Standard practice in a lab is to change pipette tips between samples.