How to survive to statistics

One of the main problems patients have when deciding where to undergo any treatment is to understand the success rates of the various clinics. Statistics are a double-edge weapon, which if carefully managed can either provide useful or confused information.

There are a few things that, in our opinion, should be taken into account when asking about the results, though due to the length of this article I will only be able to cover the issues of most importance.

 Those I would consider critical are:

            1. The more cases a clinic has the more reliable their success rates are

            2. Well-know clinics tend to “deal” with more difficult cases

            3. Not all the clinics are audited by neutral health authorities

            4. The main statistic you should ask for is “live-birth per cycle started”

 Some would consider that BarcelonaIVF being a new clinic wouldnot qualify under my first point since we don’t have a high number of cases… yet! But this article is not about what shows the clinic in the best light. I’m writing about what is important for  patients, and the fact is that having a 50% success rate seems more consistent if the clinic has carried out 500 cycles rather than just 20.

 With regards to my second point this may seem obvious but is something that patients must be aware of. Once you start publishing good results you may expect that those patients that have tried and failed several times may opt to try a new cycle at the clinic that offers them the highest chances of success. And there is a clear correlation between the number of attempts a patient has undergone and the outcome of the following attempts. Usually the results are poorer in patients with recurrent IVF or egg donation failures, so keeping good pregnancy rates become a harder issue as your reputation grows.

 This along with my forth point are the salient points of this article. You can publish whatever results you want as long as no one checks that what you’re saying is what you have. (however in our opinion and thanks to the information patients share on the net, when a clinic systematically publishes better results than what they actually have they are always exposed). This should be kept in mind when undergoing treatments in some countries. In Spain the only place where private clinics are obliged to send their results to the Public Health Authorities is in Catalonia though, unfortunately, these results are not yet available to the public. But at least as a patient you know that every clinic in Catalonia can at any moment be requested by the authorities to substantiate the results they have previously submitted. Submitting ones results to the National Registry of the Spanish Fertility Society is still voluntary and only in the last year the clinics have been audited to confirm these results. A good sign that shows that things have started to change.

 Finally, the ‘live birth rate per cycle started’. When you check the results of a clinic you are going to face a large bunch of numbers… pregnancy rate per transfer, implantation rate per embryo transferred, clinical pregnancy rate, pregnancy rate per egg collection… the list is endless.  The clinics tend to publish those results that better show what they’re good at. But in the end what the couples are seeking is a baby, and they want to know is the likelihood of achieving their dream when they start a cycle. According to this:

  • Any statistic that refers to transfers (e.g. clinical pregnancy rate per transfer) is not taking into account the cycles that have been cancelled or those in which the transfer has not taken place, something especially critical when patients are older than 40 (most of these cycles are cancelled due to poor response) or if you need a PGD (in a lot of these cases no embryo is suitable for being transferred). So what’s the point in having a 25% pregnancy rate per transfer if 80% of the patients that have started a cycle don’t even reach the transfer?
  • You need to ask about what a “cycle” means. In some cases “cycle” means all the embryos created in a single egg collection, and this “cycle” may include all the fresh and the frozen transfers that a single egg collection may lead to. That would mean that the pregnancy rate is really an “accumulated” pregnancy rate, not the success rate of single transfer.
  • Ask about what the success rate means. Maybe the clinic is talking about positive pregnancy tests, pregnancies that are able to be detected by ultrasound or pregnancies in which the embryo heart-beat can be seen… In many cases these results are not taking into account miscarriages, something that in some groups of patietns is a critical issue.
  • Live-birth means that all the miscarriages have been excluded. This is not really an issue after an egg donation, where the miscarriage rate is not high, but it could mean a lot after an IVF in women older than 38. Clinics usually provide the miscarriage rate, since in most cases they don’t follow the pregnancies, but in our opinion it would be easier to provide live-birth rates rather than expecting patients to work it out by discounting the miscarriage rate from the pregnancy rates.

 I hope that this article has shed some light on the mess that sometimes understanding the statistics can be. We’ll soon be publishing our own first results although live-births are not going to be available until October, but I’m confident however that we won’t regret writing this article. 

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