The dibucaine number, which is a measure of the enzymatic activity of pseudocholinesterase, was 81 (Normal values are > 70).
The serum pseudocholinesterase level and serum dibucaine inhibition tests were performed at the Mayo Clinic Laboratory.
It is possible that the patient had a pseudocholinesterase enzyme variant, such as the fluoride -resistant or K type, which is unlikely to be detected utilizing a standard dibucaine inhibition test.
 Nonstandard abbreviations: BChE, butyrylcholinesterase; DN, dibucaine number.
Biochemical phenotypes are defined by the pattern of values obtained after differential enzyme inhibition to determine "inhibitor numbers," e.g., the dibucaine number (DN).
The five BCHE mutations analyzed in the mutation screen were dibucaine (D70G; [Asp.sup.70] [right arrow] Gly), silent-1 (sil-1; G117FS; Gly GGT to GGAG), fluoride-1 (flu-1; T243M; [Thr.sup.243] [right arrow] Met), fluoride-2 (flu-2; G390V; [Gly.sup.390] [right arrow] Val), and K-variant (A539T; [Ala.sup.539] [right arrow] Thr; Fig.
An exon 2 region that included the dibucaine (D70G) and sil-1 (G117FS) loci was amplified as a single 570-bp fragment with primers BC14 and BC3 (Table 2).
DIRECT DNA SEQUENCING FOR DIBUCAINE AND SIL-1 MUTATION ANALYSIS
MEASUREMENT OF SERUM BCHE ACTIVITY, DIBUCAINE NUMBER AND FLUORIDE NUMBER
DN is the percent inhibition of activity caused by 0.03 [micro]mol/L dibucaine and FN is the percent inhibition of activity caused by 4 [micro]mol/L sodium fluoride .
(4) Nonstandard abbreviations: BCHE, butyrylcholine esterase; DN, dibucaine number; FN, fluoride number; SSCP, single-strand conformation polymorphism; and RFLP, restriction fragment length polymorphism.