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.