Plasma ammonia was measured with unitary stabilized reagents (multilay
er slides) in 310 dogs of various breeds, ages and sex. Frequent value
s do not depend on age (except in newborns in which they are almost tw
o times higher) nor on sex or size. They were 43 +/- 6 mu mol/l (m +/-
SD). Using 60 mu mol/l as a limit of discrimination, no increase was
observed in trauma and in diseases of the eyes, skin, endocrine and se
x glands, nervous system, pancreas, urinary tract. In animals having d
isease of the liver or of the fiver and other organs, specificity was
high : 0.95 and sensitivity was low : 0.25. As a result, negative pred
ictive value of this test is low. On the contrary, positive predictive
value is higher than 0.50 when pre-test probability is higher than 0.
16. This test is thus useless as a screening test but can be useful fo
r the diagnosis of some liver diseases when pre-test probability range
s from 0.25 to 0.75.