Early pregnancy testing is important for the health of mom and baby when it comes to prenatal care. If a woman has any health conditions that may need monitoring during pregnancy, she will need the most accurate, early pregnancy test. The accuracy of an early test is dependent on the sensitivity of the test to hCG as well as the concentration in the blood or urine. The hormone, hCG increases daily and can double in 24 to 48 hours. A test that comes up negative may need another day or two before the level of hCG becomes detectable. There are some pregnancy tests that are more accurate than others when it comes to early detection.
Blood Tests
A blood test for pregnancy is still the earliest, most accurate test, according to the Henry Ford Hospital in Dearborn, Michigan. It studied 662 female patients, giving them a blood test and a urine test for pregnancy. Six women had false negative results using the urine test. Based on these results, doctors decided to use a blood test for women that were less than four weeks past their last menstrual date to ensure accuracy. Results were presented at the Scientific Assembly of the American College of Emergency Physicians, in 2001.
If it is necessary for a woman to know that she is pregnant at the earliest possible time, a visit to the doctor is going to be the best choice. Blood tests measure the amount of human chorionic gonadotropin or hCG, a hormone produced at the time the fertilized egg attaches to the lining of the uterus. This hormone continues to increase in concentration for the next eight to ten weeks and is easily detected in the blood of a pregnant mom.
There are two types of blood tests for pregnancy. One is called a qualitative test, which either confirms a pregnancy as positive or negative. The other one is a quantitative test and provides the actual concentration of hCG in the blood. Within seven to 12 days of conception a woman can find out if she is pregnant with a blood test.
Urine Tests
The most accurate home test is one that has a high sensitivity to the hormone, hCG, and is easily read. All home pregnancy tests measure hCG in the urine. A test strip is placed in the urine stream or a sample of urine to get a measurement of the concentration of hCG. Tests have a different sensitivity to this hormone, detecting anywhere from 12.5 mIU/ml to 100 mIU/ml of hCG.
According to the University of New Mexico School of Medicine, The First Response Early Home Pregnancy Test was the most sensitive of 18 tests compared. It detected pregnancy at the 12.5 mIU/ml range. This means that it can be used early with greater accuracy. Some tests were only able to determine pregnancy at 50 mIU/ml and 100 mIU/ml of hCG. First Response claims that this test can be used as early as 6 days before a woman's missed period. The second most sensitive test in this study was the Clearblue Easy home pregnancy test.
Digital Tests
Some women find it difficult reading the results of home pregnancy tests. Digital tests are more accurate than non-digital test, according to SPD Swiss Precision Diagnostics, published by "Current Medical Research and Opinion" in 2008. They compared the digital home pregnancy test, Clearblue Digital with five non-digital tests. One hundred-twenty female volunteers read the results of the tests. Clearblue Digital detected hCG in the urine at 25 mIU/ml with 100 percent accuracy. The volunteers reported their certainty level as either "very certain" or "certain." Accuracy in the non-digital tests were 65.8 percent to 87.5 percent, with one at only 8.3 percent.
References
- Baby Hopes: Is A Blood Test For Pregnancy More Accurate Than A Urine Test?
- Doctor's Guide: ACEP: Urine hCG Tests May Miss Early Pregnancy
- "American Journal of Obstetrics and Gynecology": Accuracy of Home Pregnancy Tests at the Time of Missed Menses
- American Pregnancy Assoication: Understanding Pregnancy Tests: Urine & Blood
- Current Medical Research and Opinion: Comparison of Accuracy and Certainty of Results of Six Home Pregnancy Tests Available Over-the-Counter
