Tuesday, January 15, 2013

How to do Urine Pregnancy Test


Urine Pregnancy Test

(Human chorionic gonodotropin test)

The hCG one step test is used for the qualitative detection of human chorionic gonodotropin in urine.



Principle

Pregnancy test strips
Fig. Pregnancy test strips
The hCG one step pregnancy test is a rapid chromatographic immunoassay for the qualitative detection of human chorionic gonodotropin in urine to aid in the early detection of pregnancy. The test device consists of two lines for the result indication, the test line and the control line. The test line consists of combination of antibodies including monoclonal hCG antibody where as the control line consist of goat polyclonal antibodies and colloidal gold particles. When urine specimen is added in the wall of test device the specimen migrates along the membrane to react with the colored reconjugate via capillary action and form the colored line. Presence of colored line indicates positive result where as absence of colored line indicates negative result.

Reagents

The test device consists anti hCG particles and anti hCG coated on membrane.

Specimen collection and preparation

Fresh early morning sample should be collected in clean and dry container. Early morning sample contains the higher concentration of HCG. However urine specimen can be collected at any time of day. If precipitates seen in urine specimen it should be centrifuged and deposit should be used for the test. Specimen may be stored at 2-80C for up to 48 hrs. In delay condition specimen may be frozen and store below -20 C. Before test the frozen specimen should be thawed and properly mixed.
(Source: http://www.medicalhealthtests.com)

Procedure
  1. Bring the pouch to the room temperature.
  2. Remove the test device from the pouch.
  3. Take a fresh urine sample with the help of dropper transfer about 3 drops approximately 100 μL of urine specimen into the well of the test device. Avoid air bubbles.
  4. Through the capillary action the specimen gets transfer to the membrane. Wait for about 3 mins till the red line appears. Do not interpret results after 5 minutes as it may give false positive result.

Interpretation of Results

Fig. Interpretation for the Pregnancy test result
(1) NEGATIVE: If there is only one purple color band in the result window, this indicates that the specimen does not contain a detectable level of hCG and should be interpreted as a negative result 

(2) POSITIVE: If there are two purple color bands in the result window, this indicates that the specimen contains hCG and should be interpreted as positive result

(3) INVALID: If there is no purple color bands in the result window, the test result is invalid. The control band will not appear if an insufficient volume of specimen is added into the test kit. Proper procedures may not have been followed in performing the test or deterioration of the test kit may have occurred. Repeat the test procedure using a new test kit.

Note: The instructions provided must be strictly followed in order to achieve optimal test reactivity with the urine specimens.


Note
  1. hCG is a glycoprotein hormone produced by the developing placenta shortly after fertilization
  2. Soon after conception the hCG is seen in both serum and urine and it gets rapidly rise in concentration during early gestational growth.
  3. This test detects the presence of hCG in urine specimen at sensitivity of 25 IU/ml.
  4. During interpretation if no line seen in control it indicates invalidity, it may be due to insufficient volume of specimen or incorrect procedural techniques.
  5. The hCG can be detected in urine in other conditions also such as trophoblastic disease testicular tumors, prostate cancer breast cancer and lung cancer. Hence this test cannot be used for the diagnosis of pregnancy unless these conditions have been ruled out. If the level of hCG are below the sensitivity level of test false negative result occurs.
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