The +/- Tests: Clearblue Easy, Fact Plus, e.p.t., Target, and Equate
Infamous For False Positives? My Experiments

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Early in 2005 I began receiving numerous complaints about HPT's with a +/- results window. Many women were experiencing false positives. I am not a big believer in false positives (see The Truth About False Positives for various scenarios) but I was inundated with so many complaints (and saw similar issues reported on various fertility-related message boards) that I have come to believe that these tests are flawed in their design. I have purchased several of them and my experiments are chronicled below. Though some of these were performed on separate occasions I have integrated them below for easier comparison.

Though I have not experienced a false positive with any of these tests myself, I have used a very small sample (not statistically significant.) Overall I was not pleased with most of these tests, though some brands were less, uh, crappy than others. I don't recommend any of them with the exception of Equate-- which, while it falls under the "+/-" category, uses a pink dye rather than blue and so far seems to be evading the bad reputation earned by the others.

It is interesting and important to note that all brands of the +/- tests, with the exception of Equate, are currently being manufactured by the same company. Fact Plus and Clearblue are distributed under the name of Unipath Ltd., whose parent company is Inverness. Inverness distributes generic brand tests, including Target brand. e.p.t. is a trademark of Pfizer, but Unipath is currently manufacturing the e.p.t. test as part of a recent legal settlement. (The lawsuit involved patent infringement and the digital pregnancy test.)

Meet The Tests

	Clearblue Easy Earliest Results	sensitivity: 25 mIU
	e.p.t.	sensitivity: 25 mIU
	Fact Plus	sensitivity: 25 mIU
	Inverness (Target & other generic brands)	sensitivity: 25 mIU
	Equate	sensitivity: 25* mIU

Each test allows a 10-minute limit in which to read the results. After 10 minutes the results are invalid. I photographed each test before it was used; 1 minute after applying urine; 3 minutes after applying urine; 5 minutes after applying urine; and 10 minutes after applying urine.

I also photographed the tests 1 (and sometimes 2) days later (keeping in mind this part is only for "fun," as the results are invalid after 10 minutes.)

I have used and photographed 2 of each brand (with the exception of Equate) so there are a total of 9 tests pictured below. And just in case you want someone holding your hand though the pictures, you'll find my nifty comments next to each test! Oh, and P.S. the tests are *supposed* to be negative.

Fresh Outta The Box

	Clearblue #1	Horizontal "N" line visible before testing.
	Clearblue #2	Horizontal "N" line visible before testing.
	e.p.t. #1	Horizontal "N" line visible before testing.
	e.p.t. #2	Horizontal "N" line visible before testing.
	Fact Plus #1	Horizontal "N" line visible before testing.
	Fact Plus #2	Horizontal "N" line visible before testing.
	Inverness #1	Horizontal "N" line visible before testing.
	Inverness #2	Horizontal "N" line visible before testing.
	Equate	Pure as the driven snow.

On Your Mark, Get Set, Pee!
1 minute elapsed

	Clearblue #1	La la la. Taking our time.
	Clearblue #2	I'd have time to run to the bathroom . . . 'cept I just did.
	e.p.t. #1	Control line, check! Horizontal line, faint!
	e.p.t. #2	Where's that - again?
	Fact Plus #1	Easier to see this horizontal line.
	Fact Plus #2	Still pretty faint though.
	Inverness #1	Wowie, Target (Inverness) is winning the easy-to-read by a landslide so far.
	Inverness #2	Consistent performer.
	Equate	Equate is lookin' awful purdy.

She'll Be Comin' Round The Mountain
3 minutes elapsed

	Clearblue #1	The fuzziness adds to the mystique. Really.
	Clearblue #2	Finally developing.
	e.p.t. #1	Gettin' better.
	e.p.t. #2	I give it a C+. Or is that C-?
	Fact Plus #1	Lookin' pretty good.
	Fact Plus #2	Light but readable.
	Inverness #1	Not too shabby.
	Inverness #2	Consistent performer.
	Equate	Definitely the best of the bunch thus far.

Halfway There
5 minutes elapsed

	Clearblue #1	Are we impressed yet? I'm not.
	Clearblue #2	Horizontal line isn't much more visible than it was before it got peed on!
	e.p.t. #1	See above.
	e.p.t. #2	Ditto.
	Fact Plus #1	Decent.
	Fact Plus #2	I'm running out of pithy comments.
	Inverness #1	If you made me pick a blue +/- I'd choose Inverness.
	Inverness #2	Definitely passable.
	Equate Um, I'm sure I was doing something important at the 5-minute mark that prevented me from taking a photo of this test. Yeah . . . important.	Twinkie defense.

Pencils Down
10 minutes elapsed

	Clearblue #1	Barely a result at all. Hard to read. Yuck.
	Clearblue #2	Slightly darker negative result; still difficult to read.
	e.p.t. #1	Also hard to read, not impressed.
	e.p.t. #2	e.p.t. isn't pleasing the pee-stick lady.
	Fact Plus #1	Acceptable result.
	Fact Plus #2	Light, but acceptable.
	Inverness #1	Similar performance.
	Inverness #2	Same.
	Equate	Easy-to-read result.

So, none of the tests gave me a false positive. However, I am very unimpressed with the quality of the tests themselves. The - line on some tests (notably Clearblue and e.p.t.) is so light it's difficult to see, even in person under a bright light.

I disassembled a few of the tests after the 10-minute mark and examined the test window up close. The antibody strips (where a positive result would appear) were clearly visible. This is an excellent example of why you shouldn't take apart a test, stick it under a bright light, photograph it, and enhance the imagine with a computer graphics program-- tests are not meant to be read after the time limit, when taken apart, or when enhanced. These tests are all negative, but something will show up if you look closely . . .

Antibody Strips: Not A Positive Result

	Clearblue Easy regular & enhanced
	e.p.t. regular & enhanced
	Fact Plus regular & enhanced

And finally, here are what the tests look like a day or two later. This is another shining example (much like the Cautionary Tale) of why all negative tests should be discarded at the 10-minute mark. Results appearing after 10 minutes are invalid.

The Morning After

	Clearblue #1	A light + has appeared.
	Clearblue #2	2 days later, a light but definite + has appeared.
	e.p.t. #1	Can't see much of anything in the results window.
	e.p.t. #2	Another light but definite +.
	Fact Plus #1	Very faint-but-there +.
	Fact Plus #2 Apparently some vital task precluded my photographing a 24-hour-old urine-soaked plastic stick.	Twinkie: Double Jeopardy
	Inverness #1 Wow. Guess I slacked here too.	Up in the sky! It's a bird! It's a plane! It's a pee-stick!
	Inverness #2	Looking a little pee-worn, but displaying accurate resultss 24 hours later.
	Equate	Wow, blink and you'll miss it, huh? I've heard from women who say their horizontal line also disappeared, but their positive (vertical) line remained.

In summary . . . a true false positive is defined as a result that appears within the 10-minute time limit of a test, and is the correct color (blue on a test using blue dye, pink on a test using pink dye) when implantation of an embryo has not occurred. (There is no way to determine if conception has occurred prior to implantation. Therefore, for the 6-12 days between conception and implantation, pregnancy is entirely undetectable.)

I did not see a false positive result on any of the tests I used. Even without seeing any false positves, I was very disappointed in the quality of these tests. (I will also purchase more tests, finances permitting. If you would like to help the cause (or just say "thanks" for a cool ad-free site), please donate to my pee-stick purchase fund!) Fact Plus and Inverness (Target) did all right, but Equate was clearly superior to any of the blue-dye +/- tests. Clearblue Easy and e.p.t. were underperformers-- and ironically are the more expensive brands.

Now for a theory: if the reported false positives are indeed true false positives, the common denominator is the unique +/- design and blue dye.

A couple of years ago, when Clearblue first debuted the +/- result window, the horizontal line was not dye or ink; it was actually a sliver of blue-colored plastic (therefore unaffected by moisture.) False positives were not a problem with this design. This leads me to believe the problem lies in the fact that the dotted horizontal line overlaps with the antibody strip to form the + design.

There will always be blue dye in the horizontal line; it likely "bleeds" into the vertical line, probably depending upon how much dye is used in the test. Additionally, the blue dye is much harder to tell apart from a gray evap line than is the pink dye used in most other tests. So, I think it's likely that some tests contain more dye than others (this is common; it's just a variable of the manufacturing process), and when there is a little extra, the dye from the - line spills over into the | line. The | line is already slightly visible due to the presence of the antibody strip where a positive result would be; it is slightly gray. This gray is hard to tell apart from the blue dye, so if a tiny bit of dye bleeds over, it becomes part of the gray "shadow" and looks positive. The Equate test, which uses pink dye, does not appear to have this problem, lending more credence to my random speculation.

Ta-da!

I plan to try out another Equate test soon. Remember, you can donate to my pee-stick purchase fund to help finance my habit. Er, my scientific research.