Performance Data - Siemens IMMULITE 1000 Manual Del Usuario

In severe nonthyroidal illness, the
assessment of thyroid status becomes
especially difficult. Since some patients in
this category may suffer from concomitant
primary hypothyroidism or from a
compensatory secondary hypothyroidism,
TSH immunoassay has been
recommended as a confirmatory test in
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this context.
In rare conditions associated with extreme
variations in the albumin-binding capacity
for T4 — such as familial dysalbuminemic
hyperthyroxinemia (FDH) — direct free
thyroid hormone assays may yield
misleading results.
Circulating autoantibodies to T4, and
hormone-binding inhibitors may interfere.
Heparin has been reported to have in vivo
and in vitro effects on free T4 assays.
Hence, samples should not be collected
during or soon after the administration of
this anticoagulant.
Because EDTA would have a significant
effect on results, it should not be used as
an anticoagulant.
Heterophilic antibodies in human serum
or plasma can react with the
immunoglobulins included in the assay
components causing interference with
in vitro immunoassays. [See Boscato LM,
Stuart MC. Heterophilic antibodies: a
problem for all immunoassays. Clin Chem
1988:34:27-33.] Samples from patients
routinely exposed to animals or animal
serum products can demonstrate this type
of interference potentially causing an
anomalous result. These reagents have
been formulated to minimize the risk of
interference; however, potential
interactions between rare sera and test
components can occur. For diagnostic
purposes, the results obtained from this
assay should always be used in
combination with the clinical examination,
patient medical history, and other findings.

Performance Data

See Tables and Graphs for data
representative of the assay's performance.
Results are expressed in ng/dL. (Unless
otherwise noted, all were generated on
serum samples collected in tubes without
gel barriers or clot-promoting additives.)
Conversion Factor:
ng/dL × 12.87 → pmol/L
IMMULITE/IMMULITE 1000 Free T4 (PILKFT4-8, 2015-05-29)
Reportable Range: 0.3–6 ng/dL
(3.9–77.2 pmol/L)
The assay is traceable to an internal
standard manufactured using qualified
materials and measurement procedures.
Analytical Sensitivity:
Limit of Blank (highest value expected for
a sample with no analyte; determined in
accordance with CLSI EP17-A
0.13 ng/dL (1.67 pmol/L)
Limit of Detection (lowest detectable
concentration; determined in accordance
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with CLSI EP17-A ): 0.28 ng/dL
(3.6 pmol/L)
Functional Sensitivity: (concentration
with 20% coefficient of variation (CV)
determined in accordance with CLSI
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EP5-A2 ): 0.30 ng/dL (3.9 pmol/L)
Precision: Samples were processed in
duplicate over the course of 20 days,
two runs per day, for a total of 40 runs and
80 replicates. (See "Precision" table.)
Specificity: The antibodies are highly
specific for free T4. (See "Specificity"
table.)
Bilirubin: Presence of conjugated and
unconjugated bilirubin in concentrations
up to 200 mg/L has no effect on results,
within the precision of the assay.
Hemolysis: Presence of hemoglobin in
concentrations up to 634 mg/dL has no
effect on results, within the precision of the
assay.
Lipemia: Presence of triglycerides in
concentrations up to 1000 mg/dL has no
effect on results, within the precision of the
assay.
Alternate Sample Type: To assess the
effect of alternate sample types, blood was
collected from 49 volunteers into plain,
heparinized and Becton Dickinson SST
plastic vacutainer tubes. Ten of the
matched samples were spiked with various
concentrations of T4, to obtain values
throughout the reportable range of the
assay, and then assayed by the
IMMULITE/IMMULITE 1000 Free T4
procedure.
(Heparin) = 1.00 (Serum) – 0.004 ng/dL
r = 0.989
(SST) = 1.03 (Serum) – 0.015 ng/dL
r = 0.989
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