HCG Pregnancy Test
HCG Pregnancy Test
The hCG Pregnancy Strip Test is a rapid, self performing, qualitative, two site sandwich immunoassay for the determination of human chorionic gonadotropin (hCG), a marker for pregnancy, in urine specimens. This device is showing a visual qualitative result and is developed for professional use only.
hCG test utilizes the principle of Immuno-chromatography, a unique two-site immunoassay on a membrane. As the test sample flows
through the membrane assembly within the test device, the colored anti-hCGcolloidal gold conjugate binds with the hCG in the sample. This complex moves further on the membrane to the test region where it is immobilized by the anti-hCG coated on the membrane leading to formation of a pink colored line which confirms a positive test result. Absence of this colored line in the test region indicates a negative test result. The unreacted conjugate and unbound complex form a pink line, if any move further on the membrane and are subsequently immobilized by the anti-mouse antibodies coated on the membrane at the control region. This control line serves to validate the test results.
SET-UP OF THE TEST STRIPS
The test strip has got at the left ending the contact site for urine with a mark, which indicates the maximum immersion depth. Right next to it there is the reaction zone with the test- (T) and control- (C) region. At the right ending there is the handle to hold the strip with your fingers. This handle is covered with the abbreviation of the hormone human chorionic gonadotropin (hCG).
REAGENTS AND MATERIALS SUPPLIED
Each individual pouch contains:
• Dipstick: Membrane assembly predispensed with anti-hCG antibodiescolloidal gold conjugate and anti-hCG antibodies and anti-mouse antibodies at the respective regions.
• Desiccant pouch.
MATERIALS REQUIRED BUT NOT PROVIDED
• Specimen collection container.
1. Read the entire procedure carefully prior to performing any tests.
2. Collect the urine specimen in a clean test tube. Ensure that a sufficient quantity of the specimen is collected to allow submerging the dipping area of the dipstick (About 1 cm)
3. Bring the sealed pouch to room temperature (15-30°C), open the pouch and remove the dipstick. Once opened, the dipstick must be used immediately but latest within one hour.
4. Hold the device at the handle with the “hCG” imprints
5. Dip the area marked with max of the dipstick in the urine specimen submerging only up to the MAX mark. If urine touches the reaction zone the dipstick is defective
6. Observe for the release of the colloidal gold complex on the membrane. This would be seen as a pink moving front on the membrane and could take 10 to 15 seconds to appear depending upon the sample.
7. Remove the dipstick afterwards and place it horizontally on a flat surface. Alternatively the dipstick may be left to stand in the specimen for the entire duration of the test ensuring only the white area is left submerged in the specimen up to the “max”-mark. Read the result after 2-5 minutes.
8. If the test is interpreted after 15 minutes the sensitivity is as low as 10 mIU/mL hCG. This increase risks to get apparently false positive results due to natural abortions, elevated physiological hCG levels of nonpregnant women and drugs comprising hCG. Thus, we recommend to interpret the test after 5 minutes reaction time for routine purposes.
A procedural control is included in the test. A red line appearing in the control region (C) is considered an internal positive procedural control. A clear background in the results window is considered an internal negative procedural control. It is recommended that a positive hCG control (containing 20-250 mIU/ml hCG) and a negative hCG control (containing “0″ mIU/ml hCG) be included in each day testing to verify proper test performance.
INTERPRETATION OF RESULT
Two colored lines appear. The line in the test region (T) is the antibody probe line; the line on the control region (C) is the control line, which is used to indicate proper performance of the strip. The color intensity of the test line may be weaker or stronger than that of the control line.
Only one colored line appears in the control region (C). The presence of a test line indicates a positive result.
No line appears in the control region. Under no circumstances should a positive sample be identified until the control line forms.
LIMITATIONS OF THE TEST
Very dilute urine specimens as indicated by low specific gravity, may not contain representative levels of hCG. If pregnancy is still suspected, a first morning urine sample should be obtained 48-72 hours later and tested. Very low levels of hCG (less than 50 mIU/ml) are present in urine or serum shortly after implantation. However, because a significant number of first trimester pregnancies terminate for natural reasons (7), a test result that is weakly positive should be interpreted in conjunction with other clinical and
laboratory data. A number of conditions other than pregnancy, including trophoblastic disease and certain non-trophoblastic neoplasms including testicular tumors, prostate cancer, breast cancer, and lung cancer, cause elevated levels of hCG (>10 mIU/mL) (8-9). Therefore, the presence of hCG in urine as determined by using hCG Pregnancy Test should not be used to diagnose pregnancy
unless these conditions have been ruled out. Like with all diagnostic tests, a confirmed pregnancy diagnosis should only be made by a physician after all clinical and laboratory findings have been evaluated.
Urine hCG concentration of pregnant women rise very rapidly after implantation, reaching a peak concentration in excess of 200 mIU/ml about 2-3 months after the last menstrual period (3). hCG Test has a sensitivity of 20 mIU/ml for urine and is capable of detecting pregnancy as early as 1 day after the first missed menses. Reportedly, a level of 20 mIU/ml or more, is present 7-10 days after conception or 4-5 days prior to the first missed menses (3). Test results which appear as very light line in the test region are not definitive for the diagnosis of pregnancy. It is strongly recommended that an additional urine specimen be obtained after 48-72 hours and tested again. Negative test results in patients suspected to be pregnant should be re-tested with the first morning specimen obtained 48-72 hours later.
The test device can be evaluated 2 to 5 minutes after the addition of specimen to the test device. The analytical sensitivity of hCG Pregnancy Test is 20 mIU/mL (based on the 4th IRP of HCG). The sensitivity was established by repetitive testing of samples containing 20 mIU/mL hCG during a period of several weeks.
The hCG Pregnancy Tests do not show a “high dose Hook” or “Prozone Effect” up to the maximal observed physiological concentration
(600 IU/mL). Thus, the working range is 20 mIU/mL up to 600 IU/mL.
The specificity of the hCG Pregnancy Test was determined from crossreactivity studies with known amounts of Luteinizing Hormone (hLH), Follicle Stimulating Hormone (hFSH), and Thyroid Stimulating Hormone (hTSH). Negative results were obtained from all tests conducted with 300 mIU/ml hLH, 1000 mIU/ml hFSH and 1000 µIU/ml hTSH.
The results obtained by the hCG test correlated very well when run in parallel with other commercially available tests for pregnancy,using known positive and negative specimens.