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CD4 Counts as Surrogate Markers for Progression to AIDS
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Letters commenting on an Annals article will be considered if they are received within 6 weeks of the time the article was published. Only some of the letters received can be published. Published letters are edited and may be shortened; tables and figures are included only selectively. Authors will be notified that the letter has been received. If the letter is selected for publication, the author will be notified about 3 weeks before the publication date. Unpublished letters cannot be returned.
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TO THE EDITOR:
Choi and colleagues' recent article [1] addressing CD4 counts as an incomplete marker for zidovudine efficacy was, unfortunately, more of the same: statistical manipulation of contrived end points to justify administration of zidovudine. Having lived through a series of statistical machinations about zidovudine, I find them somewhat difficult to tolerate.
I remember when zidovudine increased everyone's CD4 cell counts; when it increased CD4 cell counts only when they were already greater than 200 × 109; when it increased CD4 cell counts for long periods; when it raised them for only a few weeks; when high CD4:CD8 ratios were good; and when CD4: CD8 ratios were no longer important (long-term survivors had high CD8 levels).
So what's new? According to Choi and colleagues, if HIV-positive patients take 500 or 1500 mg of zidovudine daily, they experience a delay in development of AIDS for a magical 16 weeks largely independent of zidovudine's effect on CD4 cell counts; if HIV-positive patients without AIDS continue this dose of zidovudine for more than 16 weeks, they continue to experience a delay in progression to the development of AIDS compared with patients receiving placebo. This delay in progression to AIDS beyond 16 weeks is attributable to a “new” statistical variable: the CD4 count compared with the total leukocyte count measured at this magical 16 weeks.
As a clinician with no financial interests in Burroughs-Wellcome and with a healthy mistrust of contrived statistics, this article left me wondering. Maybe zidovudine does work—but I do not understand why it works so differently every 2 years. Your P values look significant but my “confidence levels” have been exceeded.
Pamela Jo Harris
The AIDS Clinical REsearch Center of Washington; Washington, DC 20009
The Editors welcome submissions for possible publication in the Letters section. Authors of letters should:
•Include no more than 300 words of text, three authors, and five references
•Type with double-spacing
•Send three copies of the letter, an authors' form signed by all authors, and a cover letter describing any conflicts of interest related to the contents of the letter.
Letters commenting on an Annals article will be considered if they are received within 6 weeks of the time the article was published. Only some of the letters received can be published. Published letters are edited and may be shortened; tables and figures are included only selectively. Authors will be notified that the letter has been received. If the letter is selected for publication, the author will be notified about 3 weeks before the publication date. Unpublished letters cannot be returned.
Annals welcomes electronically submitted letters.
- Copyright ©2004 by the American College of Physicians
