How to Test for the Inhibition of Latex Agglutination From HCG

Originally, pregnancy tests involved injecting the urine of a supposedly pregnant woman into a female rabbit, mouse or frog. After 24 to 48 hours, the animal was euthanized and the ovaries inspected for evidence of haemorrhagic follicles indicating the presence of human chorionic gonadotropin (HCG) in the urine. Later a simpler test involving HCG coated latex beads and HCG anti-serum streamlined the process to a minimum of four hours. Though this method of testing for the presence fo HCG is no longer in use, the science behind the latex agglutination test for HCG paved the way for the current dye-based pregnancy test.

Things You'll Need

• Urine sample
• Test tube
• Pipette
• Centrifuge
• Latex agglutination pregnancy test kit
• Heated water bath

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Instructions

• 1

  Obtain an early morning a sample of urine from the patient, preferably the first urine of the day.

• 2

  Begin testing the sample within 12 hours. After 12 hours, the HCG degrades and the sample no longer provides a reliable result.

• 3

  Centrifuge the urine sample at 3,000 rpm for three minutes.

• 4

  Draw off the supernatant, or top layer of the urine sample, and combine the HCG anti-serum. The exact amounts of each will depend on the kit used. The HCG anti-serum may be rabbit, human or mouse.

• 5

  Mix the urine and HCG anti-serum thoroughly.

• 6

  Incubate the test tube containing the sample and anti-serum for one hour in a water bath set at 37 degrees Celsius, or body temperature. During incubation, the anti-serum will bind with any HCG present in the urine sample.

• 7

  Remove the test tube from the water bath and add the HCG-coated latex suspension to the test tube. Again, the amount will depend on the kit used. Shake the suspension thoroughly before sampling to ensure to draw off an exact amount.

• 8

  Mix the sample and latex suspension thoroughly and incubate again in the water bath for two hours.

• 9

  Remove the test tube from the water bath.

• 10

  Centrifuge the test tube at 3,000 rpm for two minutes.

• 11

  Remove the test tube from the centrifuge and compare its appearance to the positive control supplied with the testing kit. A cloudy test tube equals pregnant, and a clear test tube equals not pregnant.