Urine pregnancy test

LC is a 28-year-old woman who comes to your practice because she thinks that she is pregnant. She reports that she has not had a period in 9 weeks. When she first missed her period just over 1 month ago, she was not concerned because her cycle had become very light. However, when she missed her cycle again, she took a home pregnancy test. That test was positive. In your practice, a repeat urine pregnancy test confirms that the patient is pregnant. 

Unrecognized pregnancy remains the most common cause of amenorrhea, and a urine pregnancy test should be one of the first steps in the evaluation of this disorder. 

O Unrecognized pregnancy remains the most common cause of amenorrhea, and a urine pregnancy test should be one of the first steps in the evaluation of this disorder. To help organize an approach to diagnosis and treatment, it is helpful to consider the organs involved in the menstrual cycle, which include the uterus, ovaries, anterior pituitary, and hypothalamus. 

SMBG Self-monitoring of blood glucose UPT Urine pregnancy test... 

In the quick-start method for initiating OCs, the woman takes the first pill on the day of her office visit (after a negative urine pregnancy test). In the first-day start method, women take the first pill on the first day of the next menstrual cycle. The Sunday start method was used for many years, whereby the first pill was taken on the first Sunday after starting the menstrual cycle. 

First-morning specimens are preferred for qualitative point-of-care urine pregnancy tests because they are con-... 

Other components of the urine are conjugates with sulfuric acid, glucuronic acid, glycine, and other polar compounds that are synthesized in the liver by biotransformation (see p. 316). In addition, metabolites of many hormones (catecholamines, steroids, serotonin) also appear in the urine and can provide information about hormone production. The proteohormone chorionic gonadotropin (hCG, mass ca. 36 kDa), which is formed at the onset of pregnancy, appears in the urine due to its relatively small size. Evidence of hCG in the urine provides the basis for an immunological pregnancy test. 

Each month of therapy, the patient must have a negative result from a urine or serum pregnancy test. Repeat the pregnancy test each month prior to the female patient receiving each prescription. 

Gender cannot be tested either. As with age, there is a rumor that gender can be detected in urine, and is tested in medical insurance exams. This is another myth. It may be argued that a pregnancy test can be used to detect the gender of the urine provider, but the same test is used to detect prostate cancer in males. 

Figure 10.1 Home pregnancy testing devices, like the one seen here, utilize biotechnology techniques. This test uses paired monoclonal antibodies and colored beads to indicate increased human gonadotropin in urine. The second round well is a control, indicating the device is working properly by trapping a common urine protein.

Therapeutically, gonadotropins are used to induce ovulation in infertile women. The antiestrogens clomiphene (5.37) and tamoxifen (5.38) are also used for this purpose since they counteract the ovulation-inhihitory effect of estrogens. Pregnancy tests depend on the presence of an increased hCG concentration in the urine after fertilization. 

The enzyme attached to antibody 2 is critical for quantitative analysis. Figure 19-14 shows two ways in which the enzyme can be used. The enzyme can transform a colorless reactant into a colored product. Because one enzyme molecule catalyzes the same reaction many times, many molecules of colored product are created for each analyte molecule. The enzyme thereby amplifies the signal in the chemical analysis. The higher the concentration of analyte in the original unknown, the more enzyme is bound and the greater the extent of the enzyme-catalyzed reaction. Alternatively, the enzyme can convert a nonfluorescent reactant into a fluorescent product. Colorimetric and fluorometric enzyme-linked immunosorbent assays are sensitive to less than a nanogram of analyte. Pregnancy tests are based on the immunoassay of a placental protein in urine. 

It is important to note that with the advent of highly sensitive immunoassays for the measurement of serum and urine (3-hCG concentrations, it has been occasionally observed that postmenopausal women have slightly elevated p-hCG concentrations (typically >5 but <25IU/L). These results may cause confusion when the concentrations are above the detection limit defined for a positive pregnancy test. Although this phenomenon is not associated with pregnancy, these results are not false positives as they are routinely confirmed by alternate methods. 

Qualitative tests for CG in blood or urine are primarily used for the confirmation of pregnancy. Urine CG tests usually suffice to diagnose normal pregnancy when it has progressed beyond the first week after the first missed period. However, qualitative serum pregnancy tests can detect pregnancy earlier, and quantitative serum tests can help reveal problems in early pregnancy. 

For example, inexpensive ELISA-based pregnancy tests are now available that can measure HCG in urine accurately as early as 2 days after conception. 

The endocrine effects are interesting but not of much clinical importance. Menses may be suppressed breasts may lactate in the female or become swollen in the male. Gonadotropin, estrone, estradiol, pregnandiol, and 17-ketosteroids may be reduced in the urine. The depression of gonadotropin may lead to false negative pregnancy tests. There appears to be some central suppression of the antidiuretic hormone (6). 

One of the earliest such POC tests developed was the home pregnancy test. It is based on a qualitative immunological antibody assay. It relies on the determination of human chorionic gonadotrophin (hCG) levels in urine, which gives rise to a coloured band if positive. The device is very small and completely disposable. A quality control check is built in where the rest of the urine sample continues along the dipstick and interacts with a pH-sensitive indicator to show that the test has been performed correctly. 

Urine or blood pregnancy test in women of childbearing potential. 

Most blood proteins do not show up in the urine, but hCG does. And it is produced very soon after the egg is fertilized, and then in increasing amounts as the pregnancy progresses. Sandwich ELISA (see Figure 4.35 in the text) is the ideal method for complex biological fluids, and it is relatively easy to produce two different monoclonal antibodies to epitopes on opposite sides of the protein. All home pregnancy test kits are based on variations of this method. 

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