Expected Values; Performance Data - Siemens IMMULITE 1000 Cortisol Manual Del Usuario

Acceptable Control Range for the system,
or within an established range determined
by an appropriate internal laboratory
quality control scheme.

Expected Values

The following reference ranges have been
reported in the literature for circulating
cortisol levels and for the results of
stimulation and suppression tests.
a.m.: 5–25 µg/dL
Diurnal
Variation (138–690 nmol/L)
p.m.: Approximately
half of a.m. values
ACTH Over twice (usually 3
Stimulation to 5 times) basal
values
ACTH Reserve Below basal (control)
values
Dexamethasone Below basal (control)
Suppression values for the
screening, low-dose
and high-dose tests
Consider these limits as guidelines only.
Each laboratory should establish its own
reference ranges.
Limitations
Circulating cortisol results may be falsely
elevated in samples obtained from patients
being treated with prednisolone or
prednisone (converted to prednisolone
in vivo). Caution must therefore be
exercised with cortisol determinations for
patients undergoing therapy with these and
structurally related synthetic corticosteroids.
Heterophilic antibodies in human serum
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
4
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 µg/dL. (Unless
otherwise noted, all were generated on
serum samples collected in tubes without
gel barriers or clot-promoting additives.)
Conversion Factor:
1,8,9
µg/dL  27.59  nmol/L
Calibration Range: 1–50 µg/dL
(28–1380 nmol/L)
The assay is traceable to an internal
4,5
standard manufactured using qualified
materials and measurement procedures.
5,6
Analytical Sensitivity: 0.2 µg/dL
(5.5 nmol/L)
Precision: Samples were processed in
quadruplicate over the course of 5 days,
4,5 4 runs per day, for a total of 20 runs and
80 replicates. (See "Precision" table.)
Linearity: Samples were assayed under
various dilutions. (See "Linearity" table for
representative data.)
Recovery: Samples spiked 1 to 19 with
three cortisol solutions (109, 215 and
349 µg/dL) were assayed. (See
"Recovery" table for representative data.)
Specificity: The antibody is highly specific
for cortisol. (See "Specificity" table.)
Although some steroids exhibit
crossreactivity, their normal physiological
concentrations are low compared to
cortisol, hence they will not significantly
interfere in the IMMULITE Cortisol
procedure. There is, however, an
observed crossreactivity of approximately
49% with prednisolone which must be
considered for patients undergoing this
therapy. Since prednisone is converted to
prednisolone in vivo, caution must be
exercised with cortisol determinations for
patients undergoing either therapy.
Bilirubin: Samples spiked with 100 and
200 mg/L of conjugated and unconjugated
bilirubin were analyzed. Bilirubin may
interfere with the assay, causing elevation
of values. (See "Bilirubin" table.)
IMMULITE/IMMULITE 1000 Cortisol (PILKCO-16, 2016-02-08)