Some expensive home pregnancy tests claim to detect hCG as early as 5 days after
ID: 81723 • Letter: S
Question
Some expensive home pregnancy tests claim to detect hCG as early as 5 days after conception ( when hCG are barely there). With the knowledge of how pregnancy tests work, please describe how a pregnancy test manufacturer could create such ultra sensitive test? Some expensive home pregnancy tests claim to detect hCG as early as 5 days after conception ( when hCG are barely there). With the knowledge of how pregnancy tests work, please describe how a pregnancy test manufacturer could create such ultra sensitive test?Explanation / Answer
Pregnancy tests measure Human chorionic gonadotrophin (hCG), a hormone that is secreted in urine during pregnancy. When urine, containing hCG, is applied to the test strip, a reaction occurs which causes a portion of the stick to change color thus signaling the hormone is present and that the woman is pregnant.
The test kits on the market differ primarily by the way the user must collect and process the urine. One type of kit requires the user to urinate directly onto an absorbent area of the test kit by holding onto one end of the stick and urinating on the other. The urine is absorbed by the pad on the end of the test stick and travels along the test strip by capillary action. This design is used in products like Advance, Confirm, Clear Blue Easy, Answer, and EPT. The other type of test requires the woman to collect urine in a separate vessel. She then utilizes a dropper to deliver a precise amount of urine into a well on the test unit. Products using this design include Fact Plus, Precise, and Be Sure. Some brands, like Q Test and Answer Plus, require the woman to mix the urine with other test components before adding it to the test strip.
In addition to being present in maternal serum, hCG can be detected in the urine of pregnant women.The most advanced version of the home pregnancy test to date is able to quantify the level of hCG found in urine to provide women with an estimate of the duration of their pregnancy (in weeks since gestation).
A typical home pregnancy test contains the following components:
1.Immunoassay strip: The immunoassay strip is formed by compressing nonwoven fibers into a narrow strip and coating them with reactive antibodies. The antibodies combine with the pregnancy hormone in a series of steps, ultimately showing color change.
The immunoassay strip is coated with a protein called monoclonal antibody which reacts with hCG present in the urine and give colour change if the levels are consistent.
3.Absorbent pad: The direct application type of test contains an absorbent pad that extends from the test chamber and is used to contact the urine stream. The pad absorbs the liquid and draws it into contact with the immunoassay strip.
4. Plastic housing: The test strip and absorbent pad are contained within a two piece housing that allows the unit to be handheld and protects the strip from environmental contaminants. A leak-proof, clear plastic window on the side of the housing prevents urine from accidentally splashing on the test strip and allows the test and control zone portions of the strip to be viewed.
5.Urine collection cup: A plastic collection cup is included with test kits that require collection of urine in a separate step. They may also include plastic vials with pre-measured amounts of reagents that must be mixed with the urine before application to the test strip.
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