Editing Human chorionic gonadotropin (section)

===Methodology===

Most tests employ a monoclonal antibody, which is specific to the ''β-subunit'' of hCG (β-hCG). This procedure is employed to ensure that tests do not make [[Type I and type II errors|false positives]] by confusing hCG with LH and FSH. (The latter two are always present at varying levels in the body, whereas the presence of hCG almost always indicates pregnancy.){{cn|date=September 2023}}

Many hCG immunoassays are based on the [[Immunoassay#Two-site, noncompetitive immunoassays|sandwich principle]], which uses antibodies to hCG labeled with an enzyme or a conventional or luminescent dye.
Pregnancy urine dipstick tests are based on the [[lateral flow test|lateral flow]] technique.
* The [[urine test]] may be a ''chromatographic [[immunoassay]]'' or any of several other test formats, home-, physician's office-, or laboratory-based.<ref name="henry">{{cite book | vauthors = McPherson RA, Pincus MR |title=Henry's Clinical Diagnosis and Management by Laboratory Methods |publisher=Saunders |location=Philadelphia |year=2006 |isbn=978-1-4160-0287-1 |edition=21st}}{{Page needed|date=December 2011}}</ref>  Published detection thresholds range from 20 to 100 mIU/mL, depending on the brand of test.<ref>{{cite web| vauthors = Waddell RS | year=2006| title=FertilityPlus.org| work=Home Pregnancy Test hCG Levels and FAQ| url=http://www.fertilityplus.org/faq/hpt.html| access-date=2006-06-17| url-status=dead| archive-url=https://web.archive.org/web/20060615212054/http://www.fertilityplus.org/faq/hpt.html| archive-date=2006-06-15}}</ref> Early in pregnancy, more accurate results may be obtained by using the first urine of the morning (when urine is most concentrated). When the urine is dilute ([[specific gravity]] less than 1.015), the hCG concentration may not be representative of the blood concentration, and the test may be falsely negative.
* The [[blood plasma|serum]] test, using 2-4 mL of venous blood, is typically a chemiluminescent or fluorimetric immunoassay<ref name="henry" /> that can detect βhCG levels as low as 5 mIU/mL and allows quantification of the βhCG concentration.