Evidence based medicine has much to offer, but one has to remember Einstein’s famous remark: “Not everything that counts can be counted, and not everything that can be counted, counts.”
Mrs. R comes in to discuss some recent lipid testing. She is a 44 year old married woman with a BP of 136/72, has a minimally elevated BMI of 27, and has never smoked. She has no family history of CAD or CVA. She exercises 3-4 times weekly x 30-45 minutes either at the gym or jogging with husband. She is very careful about salt and fat, monitors her weight, resting pulse, and pre and post workout pulses and recovery time. She takes several health supplements and practices yoga for relief of stress from her job as administrative assistant for aggressive trial attorney. She had health assessment through her gym and her trainer suggested she see her doctor to talk about treating her lipids with a statin. Her total cholesterol of 260, HDL of 36 and LDL of 152. Her fasting sugar is normal. She has no symptoms.
I explain the following*: Her risk of a cardiovascular event (fatal or non-fatal MI or CVA) in the next 10 years is about 7/100. Current studies suggest that she can reduce this to just under 5/100 over a 10 year time period by taking a statin. Her NNT is 35 patients for 10 years to prevent one event. Roughly 1 person in 100 will have a serious but treatable complication from statin during that 10 years and roughly 10 will stop taking it because of non-threatening but bothersome side effects.
She says she wants to think about it and comes back in 6 weeks to discuss her plan: no medication at this time, but come in for an annual assessment of risk including lipids. She notes: “I’m pretty healthy, and I work really hard to take care of myself. My risk is low and I don’t like the idea of taking a medication to prevent something that probably isn’t going to happen anyway. My aunt takes medication for her BP and is always sick, and has lots of troubles with her medications.”
That same week, I see Mrs. B, 43 yo married teacher with a BP of 133/78, a BMI of 26. She has never smoked and has no family history of either CAD or CVA. She exercises 4-5 times weekly x 30 min jogging with friends and enjoys regular day hikes and snowshoeing with her husband. She had several surgeries as a high school athlete for knee injuries, but has no sequella and considers herself well. She comes in several months after her annual exam because a well-liked supervisor at work, an overweight male smoker, died unexpectedly of an MI. Her lab shows a cholesterol of 262, an HDL of 35 and an LDL of 150. Her fasting sugar is normal.
I explain the following*: Her risk of a cardiovascular event (fatal or non-fatal MI or CVA) in the next 10 years is about 7/100. Current studies suggest that she can reduce this to just under 5/100 over a 10 year time period by taking a statin. Her NNT is 35 patients for 10 years to prevent one event. Roughly 1 person in 100 will have a serious but treatable complication from statin during that 10 years and roughly 10 will stop taking it because of non-threatening but bothersome side effects.
At that visit she asks several questions about lab monitoring, generics and side effects, and then says she wants to take a statin and treat to an LDL of 70 if possible. “I work hard to be healthy and I feel good, but I’d hate to let all my effort to stay well go to waste because I skimped on something simple like taking a pill every evening. I know my risk of CAD is pretty low, but I certainly don’t want to blow it off and then be sorry. Bad things can happen, you know.”
These two nearly identical patients, in terms of health status and risk, had two very different responses to the evidence. What can we learn?
- Numbers do not tell us what is right or wrong. They most they can do is help clarify the relative size of the potential risks and benefits. After that, the decision is made using personal preferences and personal contexts.
- Both these patients see themselves as healthy and both are aggressive about maintaining health. Both understand their risk of cardiovascular disease is low. Both recognize the potential role of lipids for their enduring health. Despite this, they come to very different decisions because of things not so easy to measure. What explains the difference?
- One way to think of this is in terms of the availability heuristic, a common cause of cognitive bias in decision making.
- Mrs. R doesn’t picture herself as ill. Her life experience means that the most potent and available image of a medication-taker is her aunt, and she is more concerned about the potential downside of the medication. Mrs. B, on the other hand, has had a personal positive experience with medical care, and her most potent and available image is of someone dying unexpectedly of CAD.
Many clinicians see EBM as the way to answer questions and make decisions. If it were only that simple. EBM is only one step, one tool, in the decision make process. It asks us to use validated information as part of the process, a big improvement over unilateral decision making by the clinician based on the clinician’s judgement, values, and preferences (and prejudices). It isn’t either quick or easy to marshall and explain the often complicated information available, and it takes lots of time and requires both a knowledge of the patient and considerable listening skill. The hardest part, though, is always letting patients I care deeply about make decisions that are right for them, even when they are not the decisions I think I would make in the same circumstances.
(*Note: I take pains to present statistics to patients using whole numbers, and not percents or ratios. I use a consistent denominator, and round to avoid decimals. I try not to use numbers larger than 100 if possible.)