Distinguishing efficacy, individual effectiveness and population effectiveness of therapies

• Published in: AIDS (London) Vol. 14; no. 6; pp. 754 - 756
• Main Authors: Muñoz, A, Gange, S J, Jacobson, L P
• Format: Journal Article
• Language: English
• Published: England 14.04.2000
• Subjects: AIDS/HIV; Anti-HIV Agents - therapeutic use; Cohort Studies; HIV Infections - drug therapy; Human immunodeficiency virus; Humans; Population Surveillance; Randomized Controlled Trials as Topic; Treatment Outcome
• ISSN: 0269-9370; 1473-5571
• DOI: 10.1097/00002030-200004140-00020

We read with great interest the article by Phillips et al. and the editorial by Sabin regarding the effectiveness of therapies in observational studies. Although both articles laudably detail issues regarding the use of observational studies for assessing the effect of treatments, the articles highlight the need to distinguish between three epidemiological concepts: efficacy, individual effectiveness and population effectiveness of therapies. Clinical trials measure the efficacy of treatments, in which the responses of treated individuals are compared with untreated individuals, and randomization is expected to remove all confounding factors. Clinical trials demonstrate what works under controlled conditions with the limitation that the results are not necessarily applicable to real-world conditions; effects may differ in populations not represented in such trials or among those who do not precisely adhere to the prescribed regimens.