Practical
Immunology and
Serology
Hawler Medical University
College of Health Sciences
Clinical Biochemistry Dept.
Ass. Lec. Amer Ali Khaleel
(M.Sc. Clinical Immunology)
Lab.6
Pregnancy Test
(PT)
Pregnancy Test
(PT)
Introduction:
• Pregnancy tests are based on the detection of the human
chorionic gonadotropin (hCG).
• Human chorionic gonadotropin (hCG) is produced by the
placenta shortly after fertilization and reaches detectable
levels in urine and serum about 1 week after implantation
attachment of the early embryo to the uterine lining.
• Levels of hCG continue to rise during the first trimester of
pregnancy, making it an excellent marker for pregnancy.
Specimens :
•Pregnancy tests can be done by either in
urine
or in
blood
samples.
•Both tests detect the presence of a hormone called
human chorionic gonadotropin (hCG).
Urine Tests :
• Urine specimen must be collected without preservatives in a
clean dry container. First morning urine usually contains the
highest concentration of hCG, however, urine collected at
any time during the day may be used.
• If the sample put the collection container into the
refrigerator (fridge), the sample will be rejected. fridge urine
leads to less accurate results because stone forming salts
become crystallized (from the cold) and thus the results are
less viable.
Blood Tests:
• A quantitative blood test measures the exact
amount of Beta hCG in the blood by
ElectroChemiLuminescence (ECL)-based
immunoassays.
• And a qualitative hCG blood test gives a simple
positive or negative result to whether pregnant
or not (By stripes & cassettes).
Laboratory diagnosis of Pregnancy test:
No.
Methods
Time Consuming
Serology level
1
Pregnancy Test Reagent by inhibition agglutination (old method).
2 min
2
Pregnancy Test Strip or Cassette by Immunochromatography
assay.
10 min
3
Pregnancy Test by Digital Midstream Device.
3 min
4
beta-hCG Test by Electro chemiluminescence (ECL) technology .
40 min
5
beta-hCG Test by ELISA (enzyme-linked immunosorbent assay).
45 minutes –
2 hours
1-
Pregnancy Test by Strips or
Cassette
• It is a rapid chromatographic immunoassay for the qualitative
detection of human chorionic gonadotropin in urine or serum to aid in
the early detection of pregnancy.
• These pregnancy tests are specifically designed for professional users
(doctors, clinics, family planning centers) for determination of early
pregnancy, but have also found a place in home pregnancy
testing applications due to ease of use and low cost.
• The specificity is 98% meaning that test is highly selective for hCG
glycoprotein
.
Principl
e:
• The test uses two lines to indicate results; this test is
conductive by immersing the test strip in a urine or serum
specimen and observing the formation of colored lines.
• The specimen migrates via capillary action along the
membrane to react with the colored conjugate.
• Positive specimens reacts with the specific antibody –hCG
colored conjugate to form a colored line at the test line
region of the membrane. Absence of this colored line
suggests a negative result.
Procedure:
1- Bring the pouch of container to room temperature before opening
it. Remove the test strip from the sealed pouch or closed container
and use it as soon as possible.
2- With arrows pointing toward the urine or serum specimen.
Immerse the test strip vertically in the urine or serum specimen. Do
not pass the maximum line on the test strip.
3- Place the test strip on a non-absorbent flat surface, start the timer
and wait for the colored line (s) to appear.
4-Read the result after 3 minutes when testing a urine specimen and
5 minutes when testing a serum specimen.
2-Pregnancy Test by Midstream
Device.
• Is commonly used for home pregnancy testing. You can
apply the pregnancy midstream directly into the urine
stream so there is no need for urine collection.
• The accuracy of the pregnancy test is 99,6%.
• Built in quality control.
• Very high sensitivity .
• Rapid.
Gender Prediction test
(G.P.T.)
• It can be performed as early as 10 weeks of pregnancy.
• It is an easy test to perform and provides results in-home.
• Low cost when compared to sonogram (ultrasound).
• Note that IntelliGender Or Gender marker may not
predict your baby’s gender with 100% accuracy.
Notes:
• The appearance of a red line in the control window (C)
tells you that you followed the test procedure properly
and the proper amount of urine or serum was absorbed.
• Conditions other than pregnancy can cause elevated hCG
levels and positive reactions in hCG tests in the absence of
pregnancy. These include trophoblastic disease, such as
choriocarcinoma, and nontrophoblastic disease, such as
breast, ovarian and testicular tumors.
The advantages of using a blood test done
are:
• Can detect a pregnancy earlier than a urine test at about 3-10 days
from possible conception (but if a negative result is received, a test
should be repeated if a period is missed.)
• Can measure the concentration of hCG hormone in your blood (this is
useful information for your healthcare provider in tracking certain
problems in pregnancy).
The disadvantages of using a blood test done are:
• More expensive than a urine test.
• Takes longer to get result.
• Must be done in a clinical laboratory.
Any Questions