Friday, December 24, 2004

Persona vs. Clearblue

Santa knows if you've been naughty or nice, and so, apparently, do a few other people:

Sales of pregnancy tests typically soar in the first months of the year, as more women than usual tend to become pregnant -- or just think they are, according to Inverness Medical, the makers of the Clearblue Easy pregnancy tests.

Dr. Brad Imler, president of the American Pregnancy Association, told Reuters Health that most births occur in August and September -- nine months after December and January. Furthermore, winter holiday months tend to be very stressful for women, and stress can cause women to miss their period -- often the first sign of pregnancy, Imler said.

He explained that the best way to distinguish a true pregnancy from a false alarm is to focus on additional symptoms of pregnancy. These include tender or swollen breasts, fatigue, nausea, headaches, backaches and a change in appetite.


One more symptom I'd add is urinary frequency. Of note, all these additional symptoms are also useful if you're on an extended/continuous period control regimen. But I digress.

Inverness Medical is an American company who owns Unipath Ltd. Unipath is the maker of Persona, an OTC birth control method, not available in the U.S. What is available here from Inverness is the Clearblue fertility monitor.

Persona consists of a small monitor with a microcomputer, and urine test sticks. And so does Clearblue.

Clearblue
Clearblue


Persona

Although Persona and Clearblue look similar, and work on the same principle, they are not one and the same.

With Persona, you pipi on a test stick, place the stick in a monitor slot, and the monitor indicates (via lights) when you may, or may not have intercourse. Same with Clearblue, except its monitor indicates when you're most likely to conceive (most fertile). [This is how this happens: the test stick converts urinary sex hormones to something readable by the monitor. The monitor reads the hormone levels, and uses a pre-programmed algorithm to interpret the levels.]

Aha, you say, then why don't I just go ahead and use Clearblue, avoid intercourse when the monitor indicates I'm fertile, and voila!, my own little OTC birth control method. You shouldn't do that, and here's why.

Persona uses a different algorithm than Clearblue. Persona tells you when it's likely you'll become pregnant; Clearblue tells you when it's most likely you'll become pregnant. What's the difference?

Persona indicates the widest interval during which it's likely you'll become pregnant. It asks you to abstain during that entire interval, and thus offers you good protection against a pregnancy. In contrast, Clearblue indicates the narrowest interval during which you are most likely to become pregnant. If you're interested in conception, this is exactly what you want; to maximize your chances by minimizing the interval--having intercourse on the [almost] exact day when you ovulate. However, if you're interested in pregnancy protection, the narrow interval leaves you vulnerable. You want a reasonable time interval buffer on either side of ovulation.

Remember: after ovulation, an egg lives for ~12 to 24 hours; after ejaculation/penetration sperm live from 3 to 7 days.

An aside: Cervical mucus can act as a sperm reservoir, so fertilization (egg + sperm) can be removed from intercourse. This is why you can have a romantic night on Saturday, and on Wednesday, while waiting on line at the DMV to renew your license, sperm could be on its way to meet and fertilize the egg. [Something to ponder next time you're at the DMV.]

Bottom line: Persona is a birth control method. Clearblue is a fertility monitor. They should not be used interchangeably.

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12 Comments:

At 1:49 AM, Blogger alicia said...

Marquette University's nursing department has published on using the Clearblue for pregnancy prevention - you can contact Richard Fehring RN MSN PhD for more information. Or do websearch for the Marquette Model of Natural Family Planning.

 
At 2:59 AM, Blogger ema said...

alicia,

Can't find any studies in the literature on the Marquette Model. [PubMed returns only one study from Marquette Univ. about the Creighton model.]

I did find this link to an "Institute for Natural Family Planning" [don't have time to check it out, so don't know how reliable it is] where the Marquette Model of NFP is described as:

NThe Marquette Model brings 21st century technology to NFP by using the Clearplan Easy Fertility Monitor, a device used at home which measures hormone levels in urine to pinpoint ovulation. The information from this monitor is then used in conjunction with observations of cervical mucus or basal body temperatures to confidently determine the woman's fertile times.So, basically what the MM model is doing is using Clearplan to measure the LH surge for ovulation, and than relying on indirect fertility indicators (cx mucus or BBT) to guess the fertile interval. Individual indirect fertility indicators are not very reliable to begin with; combining them with a monitor programmed to indicate the fertile interval further weakens the method. As I mentioned in the post, Persona is a bc method (as opposed to Clearblue) because: it uses direct fertility indicators (E levels), and a dedicated algorithm.

 
At 9:28 PM, Anonymous Kristin W. said...

First of all, I am just wondering what your sources are for saying that clearblue gives you a shorter fertile window than persona? I'm not saying that you are wrong, I just can't seem to find any support for your statement, and I am not a fan of relying on secondary sources. I think what you are saying is very POSSIBLE, but it is also possible that these two monitors are exactly the same. I don't think you can just decide it is one way or the other without a clear statement from the manufacturer that the algorithm is different, or maybe you yourself have used both monitors at the exact same time and were given different results?

Also, I just find it very odd that you seem quite supportive of persona as a legitimate birth control option, but seem rather down on the sympto-thermal method (you say that indirect fertility indicators such as BBT and cervical fluid are not very reliable). Persona is only 94% effective, but I have yet to see any research that indicates STM as anything less than 98% effective, in fact most studies put it up to 99% or higher!

...just curious about where your information comes from!

furthermore, I am completely baffled by your logic that "combinining [BBT and cervical fluid charts] with a monitor... further weakens in the method." How is that even logical? Cross-checking ALWAYS makes a systerm more reliable, because it will make the fertile window larger. For instance, I don't think that the calendar method is in any way reliable BY ITSELF, but if I cross-check it with cervical fluid to determine the beginning of my fertile window it is VERY useful. I know that "historically" I have always been safe up until day 7. Therefore, as long as I don't see ANY cervical fluid, I consider myself infertile through day 7. However, if I see cervical fluid on day 6, my fertile window begins on day 6 that cycle. And I always consider myself fertile on day 8, cervical fluid or not. Combining two fertility indicators is used to be extra careful, NOT to get extra infertile days.

 
At 5:41 AM, Blogger ema said...

Kristin W,

First of all, I am just wondering what your sources are....

Mostly the Persona professional information booklet. It doesn't look like they have it online, but if you call them and ask for it I'm sure they'll mail you one. [The # is 08705 134952. Make sure to ask for the professional version, not the User Guide.]

Persona is only 94% effective, but I have yet to see any research that indicates STM as anything less than 98% effective....

STM is not a very effective method. Depending on the patient population, the 1st year failure rate is between 4.9% and 34.4%, with a mean of 16% with typical use.

The problem with a direct comparison between Persona and STM is that we don't have enough information to do that. (no typical use data for Persona)

Bottom line: Both STM and Persona are legitimate birth control options. The key is proper user selection.

furthermore, I am completely baffled by your logic that "combinining [BBT and cervical fluid charts] with a monitor... further weakens in the method."

I'm not sure what you're referring to here. (Bioself?)

 
At 2:36 PM, Blogger Patti said...

I have called Persona and Unipath in the past. Through persistence it was explained to me the difference in the algorithms.
Persona's programming takes into account the lifetime of sperm to avoid pregnancy.

In the other comments of "where are your sources" no one is going to find printed sources on the algorithms, those are property of Unipath and key to the operation of the monitors. The only way to know the difference of the two monitors is to call Unipath.

My long time question has been the difference (if any) of the Persona test sticks and the Clearblue Easy test sticks. Years ago Persona sticks had Persona on the cap, that was changed to a blank cap and both test sticks look exactly the same (it would be cost effective to produce the same stick for both monitors). However if you ask the company they won't give a clear answer. Persona sticks are far more expensive than Clearblue Easy sticks in the US, the only way to get Persona sticks is to purchase from UK/EU. There are only 8 per Persona box, where there are 30 per Clearblue Easy box. The sticks are the medium to collect the urine, the monitors do the computing of data/hormones.
I've read forum posts of those who have used the sticks interchangeably with no difference in monitor results.

My point is: You can use Persona for contraception or to conceive. Clearblue Easy monitor can only be used to aid conception.

 
At 7:43 PM, Anonymous Alauna said...

I use Persona to track my cycles, and I have often felt that the price for the Persona test sticks is too high. In the User Manual, it says if you forget to test one day (which has happened to me a few times) just to throw away any unused test sticks since each box has a unique batch number.

I am wondering if this is just a means to get the consumer to buy more and more test sticks?

Also, if the Clearblue test sticks really do come 30 to a box, I see no reason why I couldn't mix and match extra persona test sticks...

I am tempted to try using Clearblue test sticks with my Persona monitor, since I do not use it as my main form of birth control. Thoughts?

 
At 10:24 PM, Anonymous Anonymous said...

I have no idea if anyone is still looking at this blog, but I'm wondering if the clear blue sticks work with the Persona monitor. Does anyone know?

 
At 2:42 AM, Blogger ema said...

Anon @ 10:24 PM,

Theoretically, they should be interchangeable because 1) both are capable of capturing LH and estrogen, and 2) [I assume] it's the same technology; only the algorithm is different.

In practice, I haven't seen any data to back that up and the company is not forthcoming with a clarification.

Bottom line: As long as you're aware that there might be a risk, you can use the sticks interchangeably.

 
At 3:28 PM, Blogger Michelle said...

I've been using the "Marquette model" of nfp (to avoid pregnancy) with the Clear Plan Easy Monitor. The monitor simply helps confirm my observations, and this gives me more "green days". But I've been curious about the Persona, and I was lucky enough to find one. This is my first cycle using both, and the Persona uses the Clear Plan sticks with no problem, and both monitors accurately indicated ovulation. I am interested to see how many "green light" days I get out of the Persona monitor next cycle--this first cycle with Persona is its' learning cycle and it only gives "red light" days.

I was glad to find this thread to help answer my questions. Thanks.

 
At 4:43 AM, Anonymous Nancy Kuecher said...

Michelle,

Did you find that the ClearBlue gave you more "green days" than Persona in the second month of using both? I'm dying to know.

 
At 9:52 PM, Anonymous ovulation predictor said...

thank you for clarifying this
I'm wondering how safe is Persona?
can it be used as the only contraceptive method?

 
At 9:48 PM, Blogger Michelle said...

I have been using the Marquette model (using clear blue easy) of NFP for several years now, for contraception. I find that the clear blue easy has helped immensely to confirm my observations and avoid pregnancy. I found a Persona to try as well. Since it uses the cbe easy sticks I figured I had nothing to lose. After trying it, I decided that I like the cbe much better and stopped using the Persona. The cbe gives you more info (low fertility, high fertility, or peak-ovulation) while the persona basically breaks your reading down into red light-no sex (fertile) or green light-go for it (infertile). I like the added info of the cbe so that I can chart with confidence and have a record to look back on when the current cycle is confusing me. Plus, it seemed to me that using the cbe I got more "green light" days than with the Persona because Persona is using a very conservative Must Not Get Pregnant instruction.

 

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