So, I’ve never really understood dating. I have a complete inability to figure out what is going on. Anybody who knows me well, knows this to be the case. I do, however, like to think that I understand the basics of evidence-based medicine. I can often figure out what is going on and I often get a bit too excited about the topic.
As such, it recently fell to my good friend Heather Johnson to explain the world of dating to me in terms that I might understand. Luckily, she often knows just how to do that. Enter evidence-based dating (EBD) and the Johnson-Purdy nomogram:
For those who are unfamiliar with the Fagan nomogram, it is a tool used in clinical medicine to facilitate understanding of the result of a diagnostic test in the context of a single patient. Clinicians create an initial impression based on clinical gestalt or risk stratification tools, then they apply a diagnostic test. The result of that test either increases or decreases the likelihood of a patient having a disease. The degree to which the test will change your opinion depends on the operating characteristics of the test at hand.
How does this tool apply to dating?
Let’s say you meet someone. Maybe you find him/her attractive. Maybe you have a witty or meaningful conversation. Based on this interaction, you feel that this individual is a potential romantic partner. We can call the initial impression the “pre-test dateability.”
But how are you to know whether or not you are likely to have a successful romantic relationship with this person? Not only are there many, many variables involved, but first impressions can be misleading. You need more data.
Though Facebook stalking and subtly questioning mutual friends (i.e. gathering collateral history) can be useful, this approach will only get you so far. In order to truly determine whether the two of you have a shot of making this whole relationship business work, you actually need to spend time with them. This means actually going on a date.
The High Sensitivity Date
All dates are not created equal. Different activities have their own properties – sensitivities and specificities if you will. Take for example going for coffee, a standard (or so I’m told) first date activity. This encounter has a high sensitivity. It is the dating world equivalent of the CRP in the presentation of joint pain. You are unlikely to miss any potential suitors with this initial screening date but if you can’t stand each other for the short time it takes to finish a cup of joe then there probably isn’t much of a future. If it was tedious as hell then the possibility of a relationship has been effectively ruled out. SN(out) for the win!
Unfortunately, the first date coffee has a high false positive rate due to its poor specificity. You might enjoy an afternoon coffee with many people even if you don’t want to date them in the long run. Let’s take a minute to review the formula for a positive likelihood ratio:
A high sensitivity combined with a low specificity does not make for a strong positive likelihood ratio, and as such the post-test dateability will not change much from the pre-test dateability. Luckily, this is an iterative process and we can apply further testing.
The High Specificity Date
On date number two you may opt to go to dinner. The stakes are somewhat higher as you are committed to the activity for at least the length of the meal; the more time you spend together, the more likely it is that the conversation will turn to discriminating topics. Having the dinner at someone’s house as opposed to a restaurant will further increase the specificity of the encounter.
A word to the wise – I have been told it is possible to be too specific at this early stage in the dating game. The couple who travels together can do almost anything together, so if the two of you survive a day-trip then things bode very well indeed. That being said, many individuals in successful relationships will be less-than-enamored with their partner after several hours in a car. I have been instructed to beware of the early false negatives that come along with high specificity dates!
As we know sensitivity is often compromised for increased specificity. Highly sensitive tests are used for initial screening then more specific tests can be applied to rule in conditions- SP(in). The same basic principles of EBM may be applied to dating. The more dates you have with a person the less sensitive and more specific the encounters need be.
The High Sensitivity and High Specificity Date
Based on information from my available resources, this date does not exist. If it does, please share your wisdom.
The Bottom Line
In EBM, the right evidence needs to be applied to the right patient in the right way. In the case of likelihood ratios a test’s result must always be interpreted in the context of the pre-test probability. The same would seem to hold true for EBD. At the end of the day though practice never really makes perfect. You can theoretically understand EBM and EBD until you are blue in the face, but each new patient and each new prospective partner will bring something unexpected to the table that does not fit into one’s current understanding of medicine, the evidence or life as you know it. Like most, uncertainty makes me a bit uncomfortable but I have been told to “just go with it.” I’ve also been told not to “over think it” but I think that ship has sailed.
So, I guess epidemiology and dating aren’t so different after all, except that medical students spend a lot more time and energy on one. I’ll just let you guess which.
Stay tuned for some more evidence-based approaches to life.