First Response Early Result is the more sensitive test, capable of detecting pregnancy earlier than Clearblue’s standard options. It picks up the pregnancy hormone (hCG) at 25 mIU/mL, while Clearblue’s digital tests require twice that concentration, at 50 mIU/mL. That difference matters most if you’re testing before your missed period. Once your period is actually late, both brands perform equally well.
How Early Each Test Works
First Response Early Result is one of the few tests with FDA-reviewed data showing how it performs in the days leading up to your period. In consumer testing submitted to the FDA, it detected pregnancy 5 days before the expected period 68% of the time. That number climbed to 89% at four days before, 98% at three days before, and hit 100% from two days before onward.
Clearblue’s standard digital test, with its higher detection threshold, needs more hCG in your urine before it will return a positive. In practice, this means it’s less reliable for very early testing. If you’re the type to test at the earliest possible moment, First Response gives you a meaningful head start. If you plan to wait until after your missed period, both tests will give you an accurate result.
Pink Dye vs. Blue Dye Readability
First Response uses pink dye in its line-based tests. Clearblue, as the name suggests, uses blue. This distinction sounds cosmetic, but it actually affects how easy the result is to read. Evaporation lines, the faint marks that appear on a test after the reading window closes, are a common source of confusion. They show up as a grayish shadow that looks much more like a faint blue line than a faint pink one. That similarity makes blue dye tests more likely to be misread as a weak positive when they’re actually negative.
This isn’t a manufacturing defect. It’s a visual problem inherent to the dye color. Fertility forums are full of posts from people agonizing over faint blue lines that turned out to be nothing. Pink dye tests aren’t immune to evaporation lines, but the contrast between a gray shadow and a pink line is easier to distinguish.
Digital vs. Line Tests
Both brands sell digital versions that eliminate line interpretation entirely. Clearblue’s digital tests are more feature-rich: they display a countdown while processing, show results in words (“Pregnant” or “Not Pregnant”), and some models estimate how many weeks since conception. The display also holds the result for up to six months, which is useful if you want to save it or show someone later.
First Response’s digital option is simpler, displaying “Yes” or “No.” It works well but doesn’t offer the extras. Keep in mind that all digital tests are less sensitive than line-based tests from the same brand because the digital reader needs a stronger signal to register. If you’re testing early, a line-based First Response Early Result will outperform any digital test from either brand.
Accuracy Claims on the Box
Both Clearblue and First Response advertise “over 99% accuracy,” which can make them seem identical. That number is a bit misleading without context. The FDA requires that accuracy figure to be calculated from tests performed on or after the day of the missed period. At that point, hCG levels are high enough that virtually any functional test will catch them. The 99% figure tells you the test works correctly under ideal conditions. It tells you nothing about early detection.
The FDA also prohibits brands from claiming “100% accuracy” or “virtually 100% accuracy.” So the “>99%” language you see on every box is essentially the ceiling of what any brand is allowed to print, regardless of actual performance differences that show up during early testing.
Which One to Choose
Your best pick depends on when you plan to test and how you want to read the result.
- Testing before your missed period: First Response Early Result (the pink dye line test, not the digital) is the clear winner. Its lower detection threshold and FDA-reviewed early accuracy data make it the most reliable option for early testing.
- Testing on or after your missed period: Either brand works. At this point, hCG levels are high enough that sensitivity differences don’t matter.
- Wanting a clear, no-guesswork display: Clearblue’s digital tests remove the anxiety of interpreting faint lines. The weeks estimator is a bonus some people appreciate, though it’s a rough estimate and your doctor will confirm dating with an ultrasound.
- Concerned about false positives from faint lines: Stick with a pink dye test (First Response) or go digital (either brand). Avoid blue dye line tests if you tend to second-guess faint results.
For most people actively trying to conceive, a First Response Early Result for early testing plus a Clearblue digital for confirmation a few days later is a practical combination that covers both sensitivity and readability.