Abbott i-STAT 1 System Manual page 539

• Detection of very low levels of hCG does not rule out pregnancy.
hCG can occur in apparently healthy, nonpregnant subjects.
values double approximately every 48 hours in a normal pregnancy,
with very low levels of hCG should be resampled and retested after 48 hours.
• Specimens from post-menopausal women may elicit weak positive results
due to low hCG levels unrelated to pregnancy. With a weak positive result,
it is good laboratory practice to resample and retest after 48 hours.
• Because of the high degree of sensitivity of the assay, specimens tested as
positive during initial days after conception may later be negative due to natural
termination of the pregnancy. Natural termination occurs in 22% of clinically
unrecognized pregnancies and 31% of pregnancies overall.
practice to resample and retest weak positive results after an additional 48 hours.
• Interfering substances (such as heterophilic antibodies, non-specific proteins,
or hCG-like substances) may falsely depress or falsely elevate results.
These interfering substances may cause false results over the entire range
of the assay, not just at low levels. While this product contains reagents that
minimize the effect of these interferents, and QC algorithms designed to
detect their effects, the possibility of interference causing erroneous results
should be evaluated carefully in cases where test results are inconsistent
with clinical information. In these cases results should be confirmed by an
alternate hCG method.
• Specimens from patients who have received preparations of mouse monoclonal
antibodies for diagnosis or therapy may contain human anti-mouse antibodies
(HAMA). Such specimens may demonstrate either falsely elevated or
falsely depressed results when tested with assay kits which employ mouse
monoclonal antibodies.
i-STAT Total b-hCG assay.
• Unknown interferences from medications may affect results.
• Hook effect: no significant hook effect detected in samples up to
300,000 IU/L.
• Partially clotted samples can result in elevated hCG results as well as quality
check codes. To prevent clotting, upon drawing the whole blood sample into
a heparinized collection tube, the sample should be inverted gently at least
10 times to ensure even dissolution of the heparin anticoagulant.
• Grossly hemolyzed samples can cause a decreased alkaline phosphatase
activity, resulting in decreased detection of hCG or quality check codes.
• The i-STAT Total b-hCG assay has been characterized in whole blood
samples with hematocrit levels up to 55% PCV. Imprecision exceeding 10%
(CV) has been observed for samples with hematocrit levels above 50% PCV.
• The handheld must remain on a level surface with the display facing up during
testing. Motion of the handheld during testing can increase the frequency of
suppressed results or quality check codes. A level surface includes running the
handheld in the downloader/recharger.
Rev. Date: 14-Mar-16
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These specimens should not be tested with the
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Art: 730475-01F
Low levels of
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Because hCG
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