Doctors will often say that the medical malpractice system requires that they be perfect, a standard that no doctor can actually reach. What we are actually talking about in this setting, though, are sensitivity and specificity.
Sensitivity is how often you find something that is actually present: a true positive. Specificity is how often you don’t call something when nothing is actually there: a true negative. In other words, if you are 100% sensitive, you will find every condition, and if you are 100% specific, then every patient you find no problem in will be disease-free.
What worries doctors more are false positives, the over-calls that end up causing excess utilization that the doctor is then dunned for, and, most critically from a liability perspective, false negatives, the misses of what is actually present.
Being, well, human, every doctor will have their own mix of inclinations towards these four potential outcomes, only some of which will be conscious. How this manifest in each decision is what statisticians call Receiver-Operating Characteristics.
The crossover with liability happens in the expression of the decision that the doctor eventually makes. The question is how to accommodate both sensitivity and specificity in a way that can stand as good evidence in a lawsuit or a medical board inquiry.
This takes us back to the essential duty of care because, as a physician, you are there to do two things: detect a medical fact, which goes to sensitivity, and evaluate that fact, which goes to specificity.
For example, suppose that a cardiologist consults on a case of suspected hypertension in a hospitalized patient. After taking a full history, the doctor reports on the symptoms related to hypertension, but does not indicate certain symptoms that could be a sign of heart failure in addition to the symptoms of hypertension. The report would be fully sensitive to the symptoms related to hypertension, but not specific about the potential other, more serious complications of the findings.
In summary, perfection in sensitivity and specificity is not the standard that you are held to. Rather, doing what a reasonably prudent physician would do under the circumstances to seek relevant findings—sensitivity—and to evaluate them—specificity—and documenting that you did so is what makes you defensible.