A PRACTICAL APPROACH TO ADJUSTING FOR ATTRITION BIAS IN HIV CLINICAL-TRIALS WITH SERIAL MARKER RESPONSES

Citation
Ac. Lepri et al., A PRACTICAL APPROACH TO ADJUSTING FOR ATTRITION BIAS IN HIV CLINICAL-TRIALS WITH SERIAL MARKER RESPONSES, AIDS, 12(10), 1998, pp. 1155-1161
Citations number
21
Categorie Soggetti
Immunology,"Infectious Diseases",Virology
Journal title
AIDSACNP
ISSN journal
02699370
Volume
12
Issue
10
Year of publication
1998
Pages
1155 - 1161
Database
ISI
SICI code
0269-9370(1998)12:10<1155:APATAF>2.0.ZU;2-F
Abstract
Objectives: To illustrate a simple approach to adjusting for bias due to drop-outs (i.e., attrition bias) when evaluating the effect of a ce rtain therapy in HIV clinical trials using the mean change in plasma v iral load. To evaluate its validity and to compare its performance wit h that of another simple method for handling dropouts: the last observ ation carried forward (LOCF) method. Design: Data from a notional trea ted group of 100 patients followed up to 52 weeks were generated. Attr ition bias was introduced by mimicking selective patient dropout (i.e. , more likely in patients doing badly). Methods: The difference betwee n the true mean change in HIV RNA levels at 52 weeks and the observed mean change because of drop-outs was calculated (attrition bias). The reduction in bias obtained by using the proposed approach was then cal culated and compared with that obtained by using the LOCF method. To a ssess the performance of the methods over the entire follow-up, the me an areas under the curves were considered. Results: Our method reduced the bias by a clinically relevant amount in a variety of different se ttings. In most of our simulations, bias was reduced by a larger amoun t than that obtainable from using the LOCF method. Conclusions: The cu rrent situation is that results from trials in HIV infection are invar iably presented with no associated attempt to quantify the attrition b ias present. Attrition-adjusted plots of mean change in HIV RNA should , we believe, be presented alongside usual plots as a form of sensitiv ity analysis. (C) 1998 Lippincott-Raven Publishers.