The adoption of new model rules on medication use in racehorses has led to a spike in positive tests in Indiana.

The Indiana Horse Racing Commission (IHRC) reported Dec. 18 a total of 47 rulings (24 in Thoroughbreds and 23 in Quarter Horses) for positive tests for prohibited substances or substances over threshold levels at the 2014 race meet at Indiana Grand, in Shelbyville. An additional 15 tests currently await adjudication, of which 11 are Thoroughbreds and four are Quarter Horses.

A number of factors contributed to the record positive count, said IHRC executive director Joe Gorajec.

The two most significant factors were the adoption of Association of Racing Commissioners International Model Medication Rules with regulatory threshold levels for a large number of therapeutic medications, and the primary testing lab’s delay in reporting positive test results