# Gravindex

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**Gravindex** is an [agglutination](/source/Agglutination_(biology)) inhibition test performed on a [urine sample](/source/Urine_sample) to detect pregnancy.[1] It is based on double [antigen](/source/Antigen) [antibody](/source/Antibody) reaction. The test detects the prevention of agglutination of [HCG](/source/Human_chorionic_gonadotropin)-coated [latex](/source/Latex) particles by HCG present in the urine of pregnant women.[2]

## Procedure and results

Kits commercially available contain two [reagents](/source/Reagent); one is a suspension of HCG-coated latex particles, and the other is a solution of HCG antibodies. One drop of the urine is mixed with one drop of antibody solution for one minute on a black glass slide. One drop of the HCG-coated latex particles is added to the slide and left for one minute.

- If the level of HCG is too low, the antibodies will remain to agglutinate the HCG-coated latex particles. If agglutination occurs, the subject is not pregnant.
- If the level of HCG is high, the HCG will bind to the antibodies, and thus no agglutination with the HCG-coated latex particles occurs. If no agglutination occurs, the subject is pregnant.

## References

1. [*MCH Research Series*](https://books.google.com/books?id=ciDQAAAAMAAJ). Health Services Administration, Bureau of Community Health Services. 1974. pp. 8–9.

1. Khurana, Indu & Khurana, Ayushi (2022-07-06). [*Concise Textbook of Human Physiology - E-Book*](https://books.google.com/books?id=Q-18EAAAQBAJ). Elsevier Health Sciences. p. 422. ISBN 978-81-312-6474-4.

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Adapted from the Wikipedia article [Gravindex](https://en.wikipedia.org/wiki/Gravindex) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Gravindex?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.