Summary And Explanation - Siemens IMMULITE 1000 Manual Del Usuario

®
IMMULITE
English
Intended Use: For in vitro diagnostic use
®
with the IMMULITE and IMMULITE 1000
Analyzers — for the quantitative
measurement of non-protein-bound
thyroxine (free T4) levels in serum and
heparinized plasma, as an aid in the
clinical assessment of thyroid status.
Catalog Number: LKFT41 (100 tests)
Test Code: F4 Color: Dark Green

Summary and Explanation

The principal thyroid hormone, thyroxine
(T4), circulates almost entirely bound to
carrier proteins, chief of which is
thyroxine-binding globulin (TBG). Altered
carrier protein concentrations induce
changes in total T4 levels, and free T4
concentrations tend to stay within a tight
range. For this reason, total T4
measurements do not always reflect
thyroid status. TBG levels may vary under
different physiological conditions, such as
during pregnancy, oral contraceptive use,
1,2
and estrogen therapy.
may increase above the normal range
while free T4 remains normal.
Alternatively, patients with a dysfunctional
thyroid gland and altered TBG levels can
have normal total T4 levels, masking the
illness. Since abnormal T4 levels may
signify either abnormal thyroid function or
carrier protein variation (physiological or
pathological), free T4 measurements more
highly correlate with thyroid status than
total T4 measurements.
Principle of the Procedure
IMMULITE/IMMULITE 1000 Free T4 is a
solid-phase, enzyme-labeled
chemiluminescent competitive
immunoassay. The solid phase (bead) is
coated with monoclonal murine anti-T4
antibody. The liquid phase consists of
alkaline phosphatase (bovine calf
intestine) conjugated to T4.
The patient sample and the reagent are
incubated together with the coated bead
for 30 minutes. During this time, free T4 in
the sample competes with enzyme
2
/IMMULITE 1000 Free T4
Total T4 levels
3,4
IMMULITE/IMMULITE 1000 Free T4 (PILKFT4-8, 2015-05-29)
conjugated T4 in the reagent for a limited
number of antibody binding sites on the
bead. Unbound patient sample and
enzyme conjugate are then removed
by centrifugal washes. Finally,
chemiluminescent substrate is added to
the test unit containing the bead and the
signal is generated in proportion to the
bound enzyme.
The IMMULITE Free T4 procedure is a
direct or single test assay, in the sense
that its results are not calculated as a
function of total T4, but interpolated from a
(stored) standard curve calibrated in terms
of free T4 concentrations.
it differs from so-called free T4 index
determinations. Unlike the classic
equilibrium dialysis methods, it requires
neither a pre-incubation step nor
preliminary isolation of the free fraction by
dialysis or column chromatography.
Incubation Cycles: 1 × 30 minutes
Time to First Result: 42 minutes
Specimen Collection
The use of an ultracentrifuge is
recommended to clear lipemic samples.
Hemolyzed samples may indicate
mistreatment of a specimen before receipt
by the laboratory; hence the results should
be interpreted with caution.
Centrifuging serum samples before a
complete clot forms may result in the
presence of fibrin. To prevent erroneous
results due to the presence of fibrin,
ensure that complete clot formation has
taken place prior to centrifugation of
samples. Some samples, particularly
those from patients receiving
anticoagulant therapy, may require
increased clotting time.
Blood collection tubes from different
manufacturers may yield differing values,
depending on materials and additives,
including gel or physical barriers, clot
activators and/or anticoagulants.
IMMULITE/IMMULITE 1000 Free T4 has
not been tested with all possible variations
of tube types. Consult the section on
Alternate Sample Types for details on
tubes that have been tested.
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In this respect