The Clearblue Plus Pregnancy Test, formerly known as the Clearblue Easy +/- Pregnancy Test, is recommended for use no sooner than the day a period is due for the most accurate results. It's not the best choice for early testing, but is 100 percent accurate four days after a missed period.
Results may be difficult to interpret. Clearblue Plus claims to be 99 percent accurate when used on the day your period is due. One independent study indicates that the test is only 67 percent accurate on the day a period is expected and 100 percent accurate four days after the missed period. User reviews suggest that it's most accurate at 15 days past ovulation, around the time a period would be expected to begin in an average 28-day menstrual cycle.
Consumers frequently complain of false positives with the Clearblue Plus, but experts say false positives are generally due to something other than the accuracy of the test. False negatives are much more common in pregnancy tests and more reliably reported. Researchers who study pregnancy tests don't even include false positives in their conclusions because it relies on the test taker, not just the test.
Having said that, the fact that this test gets so many complaints indicates that it's not clearly readable, resulting in questionable accuracy for some users. Megan Clarke at PeeOnAStick.com, a respected voice in the field of pregnancy tests, doesn't recommend tests that use the plus and minus sign due to a high level of confusion reported with the results.
A blue line should appear in the control window to indicate the test is working. If it doesn't appear, the test isn't accurate. The Clearblue Plus control line is said to be reliable and clear.
Best if used around the time of your period. The Clearblue Plus Pregnancy Test isn't the best choice for early pregnancy testing, and Clearblue recommends it for use on the first day of a missed period. Officially, it can detect human chorionic gonadotropin levels as low as 25 mIU/ml, but independent and anecdotal evidence shows it can detect levels below 10 mIU/ml in a low percentage of cases. A number of users complain about an overly sensitive evaporation line, which may cause confusing test results.
Straightforward positive/negative. The Clearblue Plus test indicates pregnancy with either a plus sign for positive or a minus sign for negative. Quite a few users say results are difficult to interpret due to faintness of the second line on the plus symbol, but that seems to be more of an issue in early testing. Those who test later in their cycles, closer to the recommended time, say the plus and minus signs are simple to read and leave no doubt about the result.
Like most manual pregnancy tests, the Clearblue Plus is activated by either urinating on the tip or dipping it in a cup of urine for five seconds. The tip of the test turns pink to show urine is being absorbed. First morning urine is recommended, but otherwise no special preparation is necessary. Results can be read in three minutes. Discard the test after 10 minutes.
1. Clinical Chemistry
Review Credibility: Very Good This clinical study evaluates the urine samples of 120 known pregnant women to evaluate the claims of early pregnancy detection by six brands of tests. Researchers say Clearblue's claims of being 99 percent accurate on the day of a missed period are misleading. Study results show the test to be 67 percent accurate on that day and 100 percent accurate four days after a missed period.
Review: The Utility of Six Over-the-counter (Home) Pregnancy Tests, Laurence A. Cole, August 2011
Review Credibility: Very Good With more than 580 pregnancy test results here, the Clearblue Plus Pregnancy Test earns an overall rating of 3 stars out of 5 after about 30 reviews. Several users complain of a dark evaporation line after 10 minutes, but the test is supposed to read at three minutes. Most say it's accurate, but even those who get a true positive say it can be confusing to read. An interpretation of the submitted statistics indicates that the test is most accurate at 15 days past ovulation, the day a period would be expected to start for most women. Before that, you're most likely to get a false negative if you're pregnant.
Review: Brand: Clearblue +Plus, Editors of and Contributors to CountdownToPregnancy.com, As of April 2013
Review Credibility: Very Good The Clearblue Plus Pregnancy Test gets 3.2 stars out of 5 after about 15 reviews, with a number of users complaining of false positives. At least one reviewer who knew she was pregnant says the results are very difficult to read. Even those who get an accurate result (positive) report that the lines aren't clear.
Review: Clearblue Easy Pregnancy Test - 2 Tests, Contributors to Amazon.com, As of April 2013
Review Credibility: Very Good After more than 45 customer reviews, the Clearblue Plus earns an overall rating of 2.5 stars out of 5. Users report a high rate of false positives, even quite close to the time they expect their periods to start. There are few positive posts, but most of the feedback is older.
Review: Clearblue Pregnancy Test, Contributors to Drugstore.com, As of April 2013
Review Credibility: Very Good Parents.com describes 10 home pregnancy tests, including how they work, when and how to use them, and their costs. No scientific studies are performed. Editors list some top picks, but the Clearblue Plus Pregnancy Test isn't one of them. Emmons notes that even if the line is faint, it's still considered positive.
Review: 10 Home Pregnancy Tests (and How to Use Them), Sasha Emmons, Not dated
Review Credibility: Very Good Clarke gives an excellent overview of false positives in pregnancy tests and why they're problematic. Although she says she doesn't believe in false positives, she notes that tests with a high reported incidence -- which are most +/- tests, she says -- are too confusing and shouldn't be used.
Review: Home Pregnancy Tests: The Truth About False Positives, Megan Clarke, Not dated