Practical Immunology and

SerologyHawler Medical UniversityCollege of Health SciencesClinical Biochemistry Dept.Ass. Lec. Amer Ali Khaleel

(M.Sc. Clinical Immunology)

Lab.6

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.

Principle:

• 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.

clearblueeasy.com

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