Final answer:
The detection of hCG is useful in diagnosing pregnancy because it is a hormone produced by the placenta which maintains the pregnancy. Immunochromatographic assays or lateral flow tests are common methods for detecting hCG, where the presence of the hormone in the urine produces a colored line on the test strip.
Step-by-step explanation:
The detection of human chorionic gonadotropin (hCG) in a patient sample is particularly useful in the diagnosis of pregnancy. hCG is a hormone produced initially by the zygote and later by the placenta. It plays a critical role in maintaining the corpus luteum and thereby ensures elevated levels of progesterone crucial for maintaining pregnancy. The lateral flow test, also known as an immunochromatographic assay, is commonly utilized to detect hCG. This method involves a physical process where a patient's urine runs through a test strip that rehydrates reagents drawing the fluid along the strip. The first stripe contains antibodies conjugated to small particles that bind to the hCG antigen, which then flows on to the second stripe where a second, fixed antibody captures this complex. This interaction results in a visible colored line if hCG is present in the sample. The third stripe acts as a control to confirm the test is functioning correctly. In addition to pregnancy testing, elevated hCG levels are also monitored for certain tumors, although it cannot definitively prove the presence of a tumor, and conversely, low levels do not rule it out.