Interesting HPT article
NEW YORK (Reuters Health) - The majority of home pregnancy tests do not detect most pregnancies if used within the first day or two of a missed period, new research indicates.
Despite the fact that many tests say they can be used on the first day of a woman's missed period, investigators at the University of New Mexico at Albuquerque found that, among 18 tests, only one - First Response, Early Result - appeared to be sensitive enough to detect pregnancy in at least 95 percent of women on the first day of their missed periods.
However, all tests became more accurate over time, suggesting that home pregnancy test users should wait until at least one week after their missed period to get a more reliable result, study author Dr. Lawrence Cole told Reuters Health.
'If it's really essential to you to know whether you're pregnant as early as possible, then you must use a super-sensitive test,' Cole noted.
Home pregnancy tests measure levels of human chorionic gonadotropin (hCG) in the urine.
During the study, Cole and his colleagues measured the amount of hCG in the urine of 25 pregnant women on the first days of their first missed periods, and tested 18 brands of home pregnancy tests to determine how well they detect those levels of hCG.
The investigators found that on the first day of a missed period, the amount of hCG present in most women's urine was so low, only the First Response test appeared capable of detecting pregnancy in more than 95 percent of women.
Only 3 of the 18 tests produced a positive result when testing urine that contained the amount of hCG typically present during the second day after a woman's first missed period. By the third day, 8 tests appeared effective, the authors report in the American Journal of Obstetrics and Gynecology.
In a subsequent, still unpublished study, Cole and his colleagues found that, on the first day a woman misses her period, First Response and Clearblue Easy identified 95 and 80 percent of pregnancies, respectively, while all other tests seemed capable of diagnosing pregnancy in only 16 percent of early users, at most.
In an interview, Cole explained that many pregnancy tests likely fail to detect pregnancy because most of the hCG present in the body during the first days of pregnancy is in a modified form, for which the tests have only a weak affinity. The proportion of total hCG made up of the modified form decreases slowly over the course of pregnancy, however, and the tests therefore become more effective over time, he noted.
He added that companies that promote 'misleading' claims that their tests are 99 percent accurate are basing that statement on experiments in which their product detected 99 out of 100 pregnancies from urine that contained larger amounts of hCG than are typically present during the first day of a missed period.
Yale New Haven
Despite the fact that many tests say they can be used on the first day of a woman's missed period, investigators at the University of New Mexico at Albuquerque found that, among 18 tests, only one - First Response, Early Result - appeared to be sensitive enough to detect pregnancy in at least 95 percent of women on the first day of their missed periods.
However, all tests became more accurate over time, suggesting that home pregnancy test users should wait until at least one week after their missed period to get a more reliable result, study author Dr. Lawrence Cole told Reuters Health.
'If it's really essential to you to know whether you're pregnant as early as possible, then you must use a super-sensitive test,' Cole noted.
Home pregnancy tests measure levels of human chorionic gonadotropin (hCG) in the urine.
During the study, Cole and his colleagues measured the amount of hCG in the urine of 25 pregnant women on the first days of their first missed periods, and tested 18 brands of home pregnancy tests to determine how well they detect those levels of hCG.
The investigators found that on the first day of a missed period, the amount of hCG present in most women's urine was so low, only the First Response test appeared capable of detecting pregnancy in more than 95 percent of women.
Only 3 of the 18 tests produced a positive result when testing urine that contained the amount of hCG typically present during the second day after a woman's first missed period. By the third day, 8 tests appeared effective, the authors report in the American Journal of Obstetrics and Gynecology.
In a subsequent, still unpublished study, Cole and his colleagues found that, on the first day a woman misses her period, First Response and Clearblue Easy identified 95 and 80 percent of pregnancies, respectively, while all other tests seemed capable of diagnosing pregnancy in only 16 percent of early users, at most.
In an interview, Cole explained that many pregnancy tests likely fail to detect pregnancy because most of the hCG present in the body during the first days of pregnancy is in a modified form, for which the tests have only a weak affinity. The proportion of total hCG made up of the modified form decreases slowly over the course of pregnancy, however, and the tests therefore become more effective over time, he noted.
He added that companies that promote 'misleading' claims that their tests are 99 percent accurate are basing that statement on experiments in which their product detected 99 out of 100 pregnancies from urine that contained larger amounts of hCG than are typically present during the first day of a missed period.
Yale New Haven
