Expected Values; Performance Data - Siemens Immulite Homocysteine 2000 User Manual

Storage: 30 days (after opening) at 2–8°C
or 6 months (aliquotted) at –20°C.
Barcode labels are provided for use with
the diluent. Before use, place an
appropriate label on a 16 × 100 mm test
tube, so that the barcodes can be read by
the on-board reader.
L2HOZ: 3 labels
L2SUBM: Chemiluminescent Substrate
L2PWSM: Probe Wash
L2KPM: Probe Cleaning Kit
LRXT: Reaction Tubes (disposable)
L2ZT: 250 Sample Diluent Test Tubes
(16 × 100 mm)
L2ZC: 250 Sample Diluent Tube Caps
CCCM: A bi-level, nonhuman serum-
based Cardiac Marker Control Module,
containing homocysteine as one of four
different constituents.
Also required
Distilled or deionized water; test tubes;
controls.
Assay Procedure
Note that for optimal performance, it is
important to perform all routine
maintenance procedures as defined in the
IMMULITE 2000 Operator's Manual.
See the IMMULITE 2000 Operator's
Manual for: preparation, setup, dilutions,
adjustment, assay and quality control
procedures.
Recommended Adjustment Interval:
4 weeks.
Quality Control Samples: Use controls
or plasma or serum pools with at least two
levels (low and high) of homocysteine.

Expected Values

Homocysteine levels can vary with age,
gender, geographical area and genetic
factors, therefore it is important for
laboratories to establish their own
reference ranges based on their local
populations. Literature suggests a
reference range of 5 – 15 µmol/L for adult
males and females,
men tend to have higher levels than
women, and that postmenopausal women
tend to have higher levels than
12
premenopausal.
One hundred and twenty samples from
apparently healthy adult male and female
volunteers age 22–66 were analyzed
4
11
but also notes that
using the IMMULITE 2000 Homocysteine
procedure. The samples were drawn in
heparinized plasma tubes and kept on ice
prior to separation of the plasma from the
cells. The median value was 7.7 µmol/L,
with a central 95% range of
5.0 – 12 µmol/L.
Consider these limits as guidelines only.
Each laboratory should establish its own
reference ranges.
Limitations
Specimens from patients who are on drug
therapy involving S-adenosyl-methionine
may show falsely elevated levels of
homocysteine.
Although analysis of the parent
compounds of carbamazepine, phenytoin,
6-azauridine, and anthopterin indicate no
cross-reactivity, specimens obtained from
patients treated with these drugs, as well
as with methotrexate, nitrous oxide, and
other anticonvulsants, should be
interpreted with caution as these
substances have been shown to interfere
in some homocysteine assays.
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
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 µmol/L. (Unless
otherwise noted, all were generated on
heparinized plasma samples.)
Calibration Range: 2 to 50 µmol/L.
IMMULITE 2000 Homocysteine (PIL2KHO-14, 2007-11-20)