The Clinical Stability of Serum Cholinesterase Activity

Intra-individual variation of serum cholinesterase activity as determined in 82 normal adults studied 373 times over periods up to 5 years is found to be relatively low. The over-all coefficient of variation was 8.4, the linear correlation between the first and subsequent tests in the same person was r = .87 (first versus second test in 82 subjects) and r = .90 (first versus seventh test in 14 people). A decline of 0.66 U. from a single prior measurement when in normal health is significant at the .05 level. The clinical significance of the test is discussed.