Introduction to articles about prognosis

Prognosis is an important factor in diagnostic and treatment decisions. It can affect whether a test is ordered at all, the choice of treatment, and when a patient will return for follow-up. For example, knowing that the survival rate for 20 year survivors of breast cancer is the same as that of the general population would help you decide how often they need  mammography and clinical breast examination.  Similarly, knowing that the prognosis for men over 70 with a Gleason stage 1 or 2 prostate cancer without metastasis is the same as that for the general population would discourage you from recommending surgery or radiation for that patient.

Studies of prognosis are often (and ideally) cohort studies.  In a cohort study, a large group of individuals with (and sometimes without) the condition in question are followed over time. Case-control studies are also used to identify prognostic factors, but they are subject to additional biases. In this module, we will first learn how to distinguish these two important study designs, then move on to evaluating the relevance, validity, and results of an article on prognosis.