Equine forensic scientists from Pennsylvania have developed a novel assay for equine blood and urine samples to identify racehorses and ensure that the samples destined for drug testing were handled appropriately.

Blood and urine samples collected from racehorses by Commission employees (witnessed by the horse trainer or representative,) are sometimes challenged for breaches in the chain of custody. For example, contamination of equine samples with human samples has been reported. To confirm the source of a blood or urine sample and to minimize disputes over sample handling, a novel genetic test called the "24-plex STR" was developed.

The technique involves analyzing pieces of genetic material called short tandem repeats (STRs). These sections of DNA are amplified and analyzed to either match or exclude a match from a single blood or urine sample using 24 different STRs, including three human STRs.

Researchers tested the technique in 90 Thoroughbred and 171 Standardbred horses. According to the scientists, "the method was highly discriminating and reproducible with a probability of false identification of 1 in 10¹¹ in Thoroughbreds and 1 in 10¹³ in Standardbreds