Rabbit Pyrogen Test (RPT)
The oldest and simplest of the endotoxin detection techniques, RPT involves injecting the biological sample in question into live rabbits and waiting for a fever to develop 23,47. This method works on the principle that rabbits and humans share similar fever patterns under influence of endotoxins. It was determined that a temperature increase of 0.5°C over a time span of 180 min after injection constituted a fever 48. It was also found that it has a detection limit of approximately 0.5 EU/ml (endotoxin unit/milliliter) or around 0.05 ng of endotoxin/ml of solution 49. As rudimentary as the technique seems, a detection rate as low as 0.1 ng was considered very accurate at the time of this methods development in 1912. This technique has been praised for its accuracy; being an in vivo technique, it is easy to accept the results of the test as researchers can physically see the test subject show symptoms of infection. Seeing the test subject suffering the effects of endotoxins provides a compelling argument to the presence of endotoxins in the sample. This method is often criticized 50. The scientific world is generally moving away from live test subjects where avoidable, in particular, animal testing. While this test was once considered the best in the industry, and is still being performed in parts of Japan, today it is criticized for its need for many samples, and its near-obsolete sensitivity and accuracy compared to other methods 51.