Healthcare Professionals Clearblue Pregnancy Tests

Clearblue Pregnancy Tests

Clearblue offers a range of home pregnancy tests, all of which detect the clinically proven urinary pregnancy hormone – human Chorionic Gonadotrophin (hCG) to provide accurate and trusted results in early pregnancy testing.

How hCG is used to detect pregnancy

The hormone hCG is produced in the earliest stages of pregnancy. During early pregnancy it plays a role in survival of the corpus luteum1 and has a significant role in the implantation of the blastocyst and protection of the embryo against immune attack at the foetal/maternal boundary. The pregnancy hormone hCG is initially produced by the embryo and therefore acts as a marker for its presence.2

HCG levels rise rapidly and predictably in the earliest days of pregnancy3 and hCG can be detected in urine 9-10 days following estimated day of conception when using the most sensitive laboratory assays.4 The levels of hCG in early pregnancy have also been found to be highly similar between women.4 This makes hCG an ideal urinary marker for quickly and accurately assessing whether a woman is pregnant or not.

Clearblue Pregnancy Tests can be used up to 6 days before the missed period

Published literature shows that pregnancy hCG levels reach at least 50 milli-International Units per milliliter (mIU/ml) on the day a pregnant woman’s period is due.5-7 If a Clearblue Pregnancy Test is used from the day the period is due, it is more than 99% accurate in detecting pregnancy.8 The high sensitivity of Clearblue Pregnancy Tests means that pregnancy can be detected up to 6 days before the missed period for women who wish to test early. The graph below shows a typical rise in urinary level of hCG from the first detection of pregnancy.

Day relative to day period is due

Reference ranges for urinary intact hCG for each day of pregnancy
*From calculated day of ovulation (LH surge +1 day)
Median, 10th and 90th centiles shown. Data from 109 UK volunteers7

Not all pregnant women who test before the day their period is due will obtain a "Pregnant" result.
This is because urinary hCG levels may not yet be above the threshold for the test.

Clearblue Pregnancy Tests are rigorously tested using early pregnancy urine samples from women whose luteinising hormone (LH) surge day is known and from which the day the period is due can be reliably estimated.7 Using these samples it is possible to assess the proportion of pregnant women expected to have sufficient hCG levels in their urine sample to generate a "Pregnant" result, on each day with respect to the day of expected period. If women choose to test early with a Clearblue Pregnancy Test, the likelihood of detecting pregnancy before the day the period is due is clearly displayed on the product packaging. Any woman who tests and gets a ‘Not Pregnant’ result, but still suspects pregnancy, should test again the day the period is due if testing was done early, or 3 days later if the period is overdue.

Over 99% accurate from the day of the expected period

At Clearblue we believe that consumers need a result they can be confident in and act on, and therefore we provide pregnancy test products that deliver over 99% accuracy from the day of the expected period.8

How hCG is used to estimate the time since conception

In order to demonstrate how hCG levels relate to the timing of conception it is important to conduct studies in which the day of conception has been accurately defined. Conception time can be estimated if the LH surge day is known in the cycle in which a woman became pregnant. LH surge is well validated as a marker of impending ovulation, 9-11 and ultrasound studies of follicular rupture have confirmed that the LH surge detected in urine occurs approximately 24-36 hours before ovulation.12 As the egg survives for only around 0.7 of a day, 13 and the fertile period ends on the day of ovulation, 14 conception occurs shortly after ovulation. Therefore detection of the LH surge can be used to estimate the day of conception. Collection of urine samples from complete menstrual cycles in which the volunteer became pregnant and the LH surge is known can demonstrate the utility of hCG in providing an estimate of time since conception.

Following implantation, hCG levels rise exponentially and predictably in blood and urine so hCG has been used to estimate gestational age.15,16 Rigorous trials have shown that there is a consistent pattern to urinary hCG levels in the first few weeks following conception17 such that thresholds for the urinary hCG hormone can be assigned in order to determine time since conception in categories: 1-2, 2-3 and 3+ weeks since conception. These thresholds are employed by the Clearblue Pregnancy Test with Weeks Indicator, so that the test provides not only a ‘Pregnant’/’Not Pregnant’ result, but also an estimate of the time since conception in these week bands.

Furthermore, pregnancy duration estimates using the Clearblue Pregnancy Test with Weeks Indicator result are 97% in agreement with standard of care ultrasound results when ultrasound precision is taken into account.18,19

hCG level - Time since conception

Digital displays provide more accurate readings

It has been shown that one in four women can misread traditional line pregnancy test results..20 Clearblue Digital Pregnancy Tests contain optical readers which provide clear digital results and eliminates the human error that can occur when reading traditional line pregnancy tests.20



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  • 8 SPD data on file. Clearblue tests have been shown to be over 99% accurate from the day of the expected period when compared to a reference method in laboratory studies using urine samples supplied for pregnancy testing.
  • 9 WHO Temporal relationships between ovulation and defined changes in the concentration of plasma estradiol-17 beta, luteinizing hormone, follicle-stimulating hormone, and progesterone. I. Probit analysis. World Health Organization, Task Force on Methods for the Determination of Fertile Period, Special Programme of Research. Development and Research Training in Human Reproduction. Am J Obstet Gynecol. 1980; 138(4):383-90
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