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• Detection of very low levels of hCG does not necessarily indicate pregnancy
(5)
as low levels of
hCG can occur in apparently healthy, nonpregnant subjects.
(14,15)
Additionally, post-menopausal
specimens may elicit weak positive results due to low hCG levels unrelated to pregnancy. In a
normal pregnancy, hCG values double approximately every 48 hours.
(16)
• Patients with very low levels of hCG should be sampled and tested again after 48 hours, or tested
with an alternative method.
• Some antipsychotic agents/drugs are known to cause false positive results in pregnancy tests.
(17)
EXPECTED VALUES
hCG is not normally detected in the urine and serum specimens of healthy men and non-pregnant
women. In normal pregnancy, 20 mIU/mL hCG is reported to be present in both urine and serum 2 to 3
days before the first missed menstrual period.
(18,19)
The levels of hCG continue to increase up to 200,000
mIU/mL at the end of the first trimester.
Agreement
Urine
Urine specimens from 634 individuals were evaluated with the OSOM hCG Combo Test and the
QuickVue
®
+ One-Step hCG-Combo Test. Samples were from patients seeking confirmation of
pregnancy. The two assays were in agreement on 629 of the 634 samples. A radioimmunoassay
(DPC Coat-A-Count
®
hCG IRMA Kit) was used to quantify the five discrepant results. Three of the
discrepant samples were found to have an hCG concentration greater than 0 but less than 20 mIU/mL,
the stated analytical sensitivity of both assays, and thus were removed from the analysis. One sample
contained 0 mIU hCG/mL according to the IRMA and was scored negative by the OSOM test but
positive by QuickVue+. The remaining sample contained >500 mIU hCG/mL according to the IRMA
and was scored positive by the OSOM test but negative by QuickVue+.
Thus in this study, the OSOM hCG urine procedure had greater than 99% agreement with the
comparative test methods in the 435 specimens testing negative and the 196 specimens
testing positive.
Physician’s Office Laboratory (POL) and Laboratory Study
A proficiency panel was prepared to allow for the evaluation of the urine and serum testing formats at
three physician’s office and a clinical laboratory. A total of 80 samples were tested at each site. Purified
hCG was spiked into horse serum as well as an artificial urine matrix. Each set (40 urine and 40 serum
samples) contained negative, low positive, moderate positive and high positive samples. Each set
was tested at each site over the course of three distinct runs. 100 % of the positive and negative results
obtained by the POL operators on both urine and serum samples were in agreement with the expected
values and with the results obtained by the clinical laboratory operators.
Comparative Methods
(QuickVue+ Test and IRMA)
+ –
OSOM
®
hCG
Combo Test
+ 196 0
– 0 435
Comparative Methods
(QuickVue+ Test and IRMA)
+ –
OSOM
®
hCG
Combo Test
+ 131 1
– 0 548
Serum
Serum specimens from 691 individuals were evaluated with the OSOM hCG Combo Test and the
QuickVue
®
+ One-Step hCG-Combo Test. Samples were from patients seeking confirmation of
pregnancy. The two assays were in agreement on 679 of the 691 samples. A radioimmunoassay
(DPC Coat-A-Count
®
hCG IRMA Kit) was used to quantify the twelve discrepant results. Eleven
of the discrepant samples were found to have an hCG concentration greater than 0 but less
than 10 mIU/mL, the stated analytical sensitivity of both assays, and thus were removed from
the analysis. The remaining sample contained 0 mIU hCG/mL according to the IRMA and was
scored positive by the OSOM test but negative by QuickVue+.
Thus in this study, the OSOM hCG serum procedure had greater than 99% agreement with the
comparative test methods.
Agreement on Positive Samples: >99%
Agreement on Negative Samples: >99%
Total Agreement: >99%
Agreement on Positive Samples: >99%
Agreement on Negative Samples: >99%
Total Agreement: >99%