PROPRIETARY INFORMATION
CONFIDENTIAL MATERIAL
Assays/Reagents
Not for Customer Distribution
104
AEROSET
®
System Troubleshooting Guide
94816-107—November 2004
ALT
Ammonium Heparin Tube Not Acceptable
Ammonium heparin was removed from the list of approved
anticoagulants for ALT, ALT-A, AST, and AST-A. The reference
used to support this recommendation is
Burtis CA, Ashwood
ER, editors.
Tietz Textbook of Clinical Chemistry,
2nd ed.
Philadelphia, PA: WB Saunders, 1994:795.
This reference states:
“Elevated levels of
L
-GLD (EC 1.4.1.3) may be encountered in
some sera from patients with parenchymal liver disease. If
ammonia is also present in the serum specimen or in one of
the reagents, the GLD reaction will proceed and interfere with
the AST determination by consuming oxoglutarate and NADH.
Thus, use of ammonia-free reagents is recommended.”
ALT/AST Activated Versus ALT/AST
Differences
ALT Activated and AST Activated assays contain the coenzyme
(activator) pyridoxal-5-phosphate (P-5-P); ALT and AST assays
do not contain P-5-P. Most laboratories in the U.S. prefer
non-activated formulations, while use of activated assays is
prevalent in European laboratories. The IVD Directive is
encouraging laboratories to use activated forms of the reagent.
There is no difference in reaction, and there are minimal
differences with most patient results. The activated reagent is
useful in patients with nutritional deficiencies, where the
coenzyme P-5-P level may be decreased with resultant
decreased enzyme activity. With these patients, the activated
reagent provides an advantage because it activates enzymes
that may not otherwise be fully active if the patient has a P-5-P
deficiency.
However, ALT Activated and AST Activated assays require
reconstitution, and have shorter onboard stability than the
non-activated assays—seven days vs. 27 days.
ALT Activated
Ammonium Heparin Tube Not Acceptable
Refer to
ALT
in this section for details.