Digitals work differently. They are not meant to be broken open are interpreted by the naked eye. The usually all have 2 lines.
exactly!! From peeonastick.com
"What do the lines on a Clearblue Digital HPT mean? Can a non-preggo get 2 lines? What does the test measure?
After much speculation about this topic, my curiosity got the better of me. After the baby went down for the night, I got busy digging into the FDA and U.S. Patent records.
Ladies, my public service research for your enjoyment:
Most HPT's are pretty straightforward. They detect hCG (human chorionic gonadotropin, the "pregnancy hormone") in urine. If hCG is present, 2 pink lines (or a blue + sign) appear in the results window. If hCG is not present (or present in such a teeeeeeeeny tiny amount that it's not yet detectable), only 1 pink line (or a blue - sign) appear in the results window. The problem with this is, of course, that a hormone-crazed woman must read the results accurately. And for some of us, reading the results accurately means refraining from photographing in high resolution and adjusting color contrast, balance, solarizing . . . disassembling tests and holding them up to windows and/or halogen light bulbs . . . begging the test to cooperate and produce a second pink line . . . I digress. The point is, the tests results requireinterpretation and face it, there is some ambiguity in faint lines, time limits, evap lines, etc.
So the Clearblue Easy Digital (and e.p.t. Certainty) take away the need for interpretation with a digital display that says either "Pregnant" or "Not Pregnant." No lines to analyze. No color adjusting. No halogen bulbs. NO FUN!
When the test strip is ejected from the digital reader, however, there are lines on it. And, because it's in our nature, we peestickaholics ("Hi Meg!") want to analyze those lines. The test instruction booklet says the lines "must" be disregarded. But . . . why? Doesn't the test work the same way as every other HPT? Don't 2 lines = pregnant???
So, after the baby went down, I pulled up the FDA website and U.S. Patent and Trademark Office site and waded through FDA applications and patent documents. I was a woman with an obsession. Er, mission. And now I will share the Secret of the Digital with you.
The first piece of interesting information I uncovered was this: the digital HPT is classified by the FDA as a "Urine hCG By Visual Color Comparison Test." However, the patent information (U.S. Patent Number 5,622,871) makes it clear that the "visual color comparison" isnot done by the naked eye. (By the way, when I say "makes it clear," I mean "uses the most technical, convoluted gobbledygook possible." The text of the patent mentions "a hollow casing constructed of moisture-impervious solid material containing a dry porous carrier which communicates directly or indirectly with the exterior of the casing such that a liquid test sample can be applied to the porous carrier." Now, I am an English snob-- I even use correct punctuation and capitalization in my e-mail-- but I would have said, "a waterproof handle with a wick that sucks up the pee.") Like so many other people, however, they didn't ask me ;)
Back to the test.
In simple terms, the digital test stick sucks up urine like a "regular" HPT. The test has a control line like every other HPT, to indicate the test worked properly. Then there is a "results zone" where a second line may or may not appear. Here's the difference: the second line may appear even if you are not pregnant, because the antibodies in the "results zone" are NOT testing ONLY for pregnancy hormone. Drumroll please. The "results zone" detects not only hCG (pregnancy hormone) . . . but also LH (luteinizing hormone.) LH is found in women's bodies almost all the time in some quantitity.(See the Fertility Info section for the nitty-gritty.) So, depending upon where you are in your cycle, how much LH your body produces normally (which can be thrown off by conditions like PCOS), you may see a second line even when there is no hCG ("Not Pregnant.")
Next question: Why does this HPT detect LH as well as hCG? After all, the presence of LH (or lack thereof) has no bearing on pregnancy detection.
Well, the best I can do there is quote the patent itself: "The determination of the presence of more than two (is multiple) [sic] analytes in any sample may have significant clinical utility." (Then it cites some examples in tests for heart disease and diabetes.) It does not elaborate further on the hCG/LH connection . . . so, in light of the fact that Clearblue just came out with a (disposable) digital ovulation predictor kit, my guess is the technology is the same in both tests and the company can use interchangeable parts and have the same patent cover both products.
Last question: How does the digital reader know what the result is?Here's the patent again: "... a standard curve can be generated by running strips with samples with known concentrations of E-3-G BI [the antibody "cocktail" with the dye/antibodies that detect the hCG and LH]. The colour at the immobile zone can be read, for example using a Minolta chromameter, and the concentration of E-3-G calculated by extrapolating from the reflectance value." In other words, your pee reacts with the reagents, makes a line (or doesn't), and the digital holder reads the specific intensity/color of the line,NOT SIMPLY determining whether a second line exists. (A "chromameter" just measures the shades of various colors-- so when teeth-whitening products say they'll lighten your teeth "at least two shades," they're basing those measurements of shades on a chromameter's reading.)
To recap: most women will normally see 2 lines on the Clearblue Digital test, pregnant or not, simply because of the normal, average, boring presence of LH. Our naked eyes cannot determine the "shade" or "intensity" of the second line, meaning our naked eyes can't make heads or tails out of the result. When the display says "Not Pregnant," believe it, until proven otherwise. (Note: Clearblue publishes the sensitivity of the digital test at 50 mIU/mL, but when questioned on their 800 line, they say 25. e.p.t. Certainty publishes their sensitivity as 50 mIU/mL as well. See the HPT FAQ for more info on why different tests work at different times-- and also why it is possible to receive a negative result and still be pregnant.)
Hanging up my Sherlock Holmes cap for the evening . . .
~Meg"
Quoting BabyDust77:
The digi tests always have two lines. Thats why they tell u not to open them.
Christian wife and mother
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- s_toman7
on Feb. 10, 2012 at 4:32 PM