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deviation of 3.2. The central 95% tendency of the range, assuming a gaussian distribution, was 0.9 to 13.5 U/h. The

central 95% of the reference data, estimated nonparametri- cally, was 1.6-15.2 U/h. One value (35.2 U/h) was removed

before

data

analysis;

no

pathological

or

pharmacological

cause for the high urine

amylase

activity

in this individual

was apparent. The mean (and SD) urinary amylase activity

(UIL) was 165(101). Urine amylase activity

specimens excretion

was significantly

correlated

rate

(U/h):

r

=

0.58,

P

<iO.

with

(UIL) in the 95 the calculated

The stability of urine amylase was evaluated

in urine

specimens individuals serum and pancreatic

from

three

in

whom

healthy individuals

and from

above-normal

amylase

activity

two in

urine resulted from abscess, respectively.

acute

pancreatitis

and a

Urine

from healthy

indi-

viduals retained

at least 80% (mean

amylase from the

activity

during

five days

of

two

patients

with

pancreatic

= 89%) of its original storage at 5#{17U}rin.e disorders retained at

least 84% (mean = 87%) of original five days at 5 #{176}C.

amylase activity

after

Discussion

The present study provides results that

indicates

that

compare

well

the direct amylase with those obtained

test by

use (or

of the more familiar

auxiliary)

enzyme.

approach that requires a coupling

The

elimination

of

auxiliary

en-

zyme(s)

in

amylase

assays

and

the

use of a defined substrate

have been recognized

reference

method

(12).

as desirable

The

direct

features for an amylase and comparison methods

were similarly urinary enzyme

precise (Table 1) and

activities.

Moreover,

gave similar

values for

their

relative

respons-

es

to

purified

human

pancreatic

and

salivary

amylases

were

essentially identical. studies whether the

It is not known, new substrate

however, from

these

in a different

buffer

would produce this same pattern

of response to the two

human isoenzymes.

It is clear from the data in Table

the two methods control materials.

may give very different results with Such differences in amylase activity

1 that some

mea-

sured noted

in control materials

before

(13-15),

and

by different

probably

result

methods have been from the biological

sources of the aniylase enzyme in the quality-control als.

materi-

The stability often important.

of amylase activity

An

incidental

finding

in various

samples

of this

study

was

is

that

the

amylase

the

exception

activity

in the quality-control

of

UriChem)

was

stable

at

5

materials (with #{1for}at least 48

h, and amylase activity in specimens from both healthy

several individuals

selected spot urine and patients with

pancreatic disorders appeared to be stable at 5#{1 for at least

five days in serum

after from

collection. Reportedly pancreatitic patients

(16), amylase

activity

is unstable,

whereas

activity

in

serum

from

healthy

individuals

is

stable

for

22

h

at various

sample

did

storage temperatures. The not indicate any difference

data from our small

in

the

stabilities

of

amylase

activity

in

or

individuals

with

urine specimens from pancreatic disease.

healthy

subjects

With few exceptions,

urine

specimens

by

amylase the direct

activities measured and comparison

in fresh methOds

agreed within a few percent, and linear regression analysis

produced equivalent

measurements

or

the

correlation

means

of

data whether

duplicates

were

individual used in the

analysis. In this first of duplicate

study, regression determinations.

analysis was

based on the

We conclude

that there is

no need, in routine duplicate.

use, to measure

urinary

amylase

in

756 CLINICALCHEMISTRY, Vol. 34, No. 4, 1988

Few recent reports

include reference intervals

amylase excretion results previously

rate, but

our

results compare

obtained

in

our laboratory

for urinary closely with and with a

reference range reported measures production of scheme. The non-gaussian

by Tietz

(17) for a method that

NADH in a distribution

multi-step reaction of reference values

for

urinary

amylase

excretion

is

in

contrast

to

a

previous

study (18), which reported a normal tion for 2-h urinary amylase activity

(i.e., gaussian) distribu- in normal individuals.

predictor of

amylase

excretion rate

(standard

error of the

estimate

=

2.6 U/h)

in a healthy

reference

population;

Total

urinary

amylase

(U/L)

activity

was a reasonable

however, a greater expected for a patient much more variable.

error in such an population, whose

estimation

can

be

hydration

status

is

The direct method for aniylase appears to be a simple and

precise alternative

to

other methods

that require

the use of

auxiliary method

(or coupling) demonstrate

enzyme(s). The that results for

present studies of this urine are comparable

with those of ence interval These findings

the comparison

method and provide a refer-

for the excretion suggest that the

rate for amylase new method will

in urine. prove to be

a useful aid emia and in

in the

the differential

diagnosis of hyperamylas-

laboratory

diagnosis

of

acute

pancreatitis.

Reagentsand financial support for a part of this evaluation were provided by Behring Diagnostics, Division of American Hoechst Corporation.

References

1. LadensonJH, McDonald JM, Bruns DE, Mauck JC. Washington University CaseConference.Acute pancreatitis, hyperlipemia, and normal amylase. Clin Chem 197824:815-20.

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DE. and

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critical review. reference system

In: for

clinical enzymology: proceedings of

the

workshop.

Madison,

WI:

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1986;51-60.

A,

Bailly M. Suit-

of

alpha-amylase

activity.

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Chem

1981;27:806-15.

13. Bretaudiere J-P, Rej R, ability of control materials

Drake P, Vassault for determination

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