LD1: Seralyzer
57.6 UIL; n
=
=
0.60 Cobas Bio
-
21 U/L, r
=
0.98; S
=
79; activity range 50-1000 U/L
The significantly lower results from the Seralyzer probably reflect sub-optimal reagent concentrations in the test
strip.
Seralyzer reference ranges were derived from those previously established for the Cobas Bio assay. Thus, for an
appropriate clinical history, an Wi >50 UIL and representing >25% oftotal LI) activity indicates myocardial damage.
Seralyzer inisciassifications
with reference to Cobas Bio
results totalled 10% (specificity 85%, sensitivity 95%).
We conclude that Seralyzer LD1/LD analysis providesa
quick, reliable alternative to wet chemistry, and is especially suited to small numbers or infrequent requests, because
all reagents used are stable and require no advance preparation.
References
1. Lott JA, Stang JM. Serum enzymes and isoenzymes in the
diagnosis and differential diagnosis of myocardial ischemia and
necrosis. Clin Chem 1980;26:1241-50.
2. Adan J, BernsteinLH, BabbJ. Lactate dehydroxygenaseisoenzyme-JJtotal ratio: accurate for determining theexistence of myocardial infarction. Cliii Chem 1986;32:624-8.
Cost-Effective ModificatIon of the Hypronosticon
Procedure for Urinary Hydroxyproline, J. E. Buttery and
S. Stuart (Dept. of Clin. Chem., The Queen Elizabeth
Hospital, Woodville, Australia 5011)
We modified the use of the Hypronosticonkit (Organon
Teknika, Boxtel, Holland) for the assay of urinary hydroxyproline, primarily to extend thenumber ofassays in thekit.
Hydrolysis of each test urine, with added hydroxyproline as
the internal standard, is omitted. Instead, a tube containing
aqueous hydroxyproline standard is hydrolyzed; aliquots
from this are added to every hydrolyzed urine sample to
serve as the internal standard.
The hydrolysis step involves a blank, a test urine (0.5
mL), and the given standard (0.5mL). After the overnight
acid hydrolysis and dilution to the 2.5-mL volume, the. color
development is processed according to the following scheme,
in 10-mL polypropylene tubes.
Volume,mL
Blank
Blanksupemate
Urine test
Hydrolyzed std.
0.5
Isopropanol
ChIoramine
T
Ehrlich’s
reagent
0.5
0.25
5
Test (7)
0.5
0.25
5
(
The inhibitory effects of ascorbic acid on enzymatic cholesterol determinations and other peroxidase reactions are well
documented (1). Recently,we experienced a total inhibition
of the cholesterolassay in the Olympus Demand. The
reagents for this assay are obtained from Cooper Biomedical. We obtained a serum cholesterol value of 0 mmoIJL for
an inpatient at our hospital on his first day of admission,
and this led us to investigate the reason for this obviously
inaccurate result.The cholesterol value for this specimen
with use of Liebermann-Burchard
reagent was 2.9 mmolJL
and the ascorbic acid concentration was 9255 imoIJL (normal 30 to 110 tmoI/L). The patientwas a 71-year-oldman
with pancreatic cancer who had been losingweightforsome
time, and because of this and his decreased appetite had
been taking many vitamins and food supplements. Three
days after admission the cholesterol
value obtained in the
Olympus Demand was 2.9mmoLIL (3.0mmol/L by Liebermann-Burchard)
and the ascorbic acid concentration was
113 .tmo1/L.
To samples from a serum pool with a cholesterol value of
4.9 mmol/L we added a constant volume of freshly prepared
ascorbic acid solutionsto give final concentrations of 100 to
6000 pmol/L. These specimens were then assayed in duplicate in the Demand and in the TDx. An interferogram as
described by Glick et al. (2) of the effect of ascorbic acid on
the cholesterol assay for the Demand and for the TDx is
shown in Figure 1.
Q
0
‘
0.25
0.25
0.5
0.25
Cap the tubesand mix. Placein a 60#{176}C
water bath for25
min. Cool for30 mm in water at room temperature. Measuretheabsorbance at 560 nm against the blank.Calculate
results as follows:
=
(Dept. of Pathol., Prince George’s Hospital Center,
Cheverly, MD 20785)
:3
(To all tubes add I dropof I moilL HCI)
U-Hydroxyproline,moi/i4
Ascorbic Acid Interferogram for Cholesterol in the
Demand and TDx, C. H. Peddicord and W. A. Barnes
><
Test + std (TS)
0.25
0.25
-
between the results (paired t-test, n = 14).The mean ± SD
were 191.8 ± 131.7 and 190.1 ± 131.4pmol/L, respectively.
Our modification for one resin tabletper urine is costeffective forsmallorlargebatchanalyses.The hydrolysis
of
each urine isdone in singleton.
T) x stcl.concn.
Comparison of the results by our modified method with
those by the kit method showed no significant
difference
:3
:3
LL
Ascorbic
acid
(umol/L)
Fig. 1. interferogramshowingeffectof ascorbicacid on results for
cholesterol
0, Demand;I, TDx
CLINICAL CHEMISTRY, Vol. 34, No. 4, 1988 773