Principles behind practice. 4. Natural history.

Abstract

The busy clinician is confronted daily with a wide range of decisions about patient diagnosis and management. The sharpness and scepticism to constantly ask fundamental questions about the natural history of a patient's disease is a talent that a few lucky individuals have. For the rest of us, it is an acquired skill which must be developed and maintained. We suggest the following questions to guide the clinician in taking account of the natural history of disease in everyday clinical practice. How strong is the evidence that the putative consequence of this illness is or is not attributable to some external factor? Can I be sure that this exposure (drug, surgery, social or behavioural therapy, toxic or environmental agent) does not have a long latency and that subsequent development of illness will not ensue? What do I know from long-term prospective studies about the life history of this disease? Does lead time explain the apparent benefit of this diagnostic test or other screening procedure? Does the evidence of the natural history of this disease specifically relate to the characteristics of my patient--age, sex, set of prognostic factors, selected or unselected referral? Is there good evidence from at least one good randomised controlled trial with a "no treatment" control group that this intervention is efficacious (and not hazardous)?