Pregnancy and diagnostic testing

What is Human Chorionic Gonadotropin (hCG)?

Human chorionic gonadotropin (hCG) is produced by the placenta shortly after fertilization (around the 4th day after conception), and reaches detectable levels in urine and serum about 1 week after implantation attachment of the early embryo to the uterine lining. hCG can be detected in urine or serum in minute quantities around day 23, or 5 days before the expected menstruation. Levels of hCG continue to rise during the first trimester of pregnancy, making it an excellent marker for pregnancy.

hCG is a glycoprotein composed of an alpha subunit and a beta subunit. hCG is closely related to two other gonadotropins, luteinizing hormone (LH) and follicle stimulating hormone (FSH), as well as thyroid stimulating hormone (TSH), all three of which are glycoprotein hormones.

hCG levels rise rapidly, doubling approximately every two days, and peak around 100,000-200,000 mIU/mL in the latter part of the first trimester of pregnancy. In normal subjects, hCG in urine provides an early indication of pregnancy.

Pregnancy and diagnostic testing


HCG circulates as an intact molecule in the serum of women who have an uncomplicated pregnancy. Subunits are cleaved rapidly and cleared promptly by the kidney. As a result, the urine contains intact hCG, and alpha and beta subunits; however, only intact hCG and beta subunits retain immunologic specificity in urine.

hCG levels vary a great deal in patients with trophoblastic disease (such as
choriocarcinoma) and certain nontrophoblastic neoplasms (such as breast, ovarian and testicular tumors). Therefore, the possibility of having these diseases must be eliminated before an accurate diagnosis of pregnancy can be made.

Pregnancy and diagnostic testing


Pregnancy tests can be performed using either urine or blood samples.

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-containing collection container is placed in the refrigerator, the sample becomes unusable. Refrigerated urine leads to less accurate results, because stone-forming salts become crystallized at low temperatures.

Blood tests:

A quantitative blood test measures the exact amount of Beta hCG in the blood by electrochemiluminescence (ECL)-based immunoassays. On the other hand, a qualitative hCG blood test gives a simple positive or negative result regarding pregnancy. The latter method uses strips and cassettes.

Pregnancy and diagnostic testing

What is the K-hCG Pregnancy Dip Strip?

The K-hCG Pregnancy Dip Strip is a rapid chromatographic immunoassay for the qualitative detection of human chorionic gonadotropin in urine, to aid in the early detection of pregnancy. 


The test utilizes a combination of antibodies, including a monoclonal hCG antibody, to selectively detect elevated levels of hCG. The assay is conducted by dipping a strip into the urine sample and observing the formation of one or two colored lines. The control line is composed of goat polyclonal antibodies and colloidal gold particles. 

The specimen migrates via capillary action along the membrane to react with the colored conjugate. Positive specimens react 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. To serve as a procedural control, a colored line will always appear in the control line region, indicating that the proper volume of specimen has been added and membrane wicking has occurred.

Pregnancy and diagnostic testing

What specimen types should be used?

Urine specimen must be collected in a clean and dry container. A first-morning urine specimen is preferred.

Pregnancy and diagnostic testing

How should it be used and at what time?

The hCG hormone can be detected in both urine and serum or plasma as early as 7 to 10 days after conception. The KBS-hCG pregnancy Rapid Test Strip for urine has a sensitivity of 10 mIU/ml, and is capable of detecting pregnancy as early as one day after the first missed menses.

Pregnancy and diagnostic testing

How to interpret the results?


Two distinct colored lines appear. One line should be in the control line region (C), and another line should be in the test line region (T). One line may be lighter than the other; they do not have to match.


One colored line appears in the control line region (C). No line appears in the test line region (T).
Invalid: the result is invalid if no colored line appears in the control line region (C), even if a line appears in the test line region (T). The test should be repeated with a new test strip.