Letters.

Looks are everything

I read with interest "Where the gems are" (SN: 3/11/00, p. 175), on determining the origin of emeralds by measuring oxygen isotopes. While there is great potential for legal and historical applications, I think that using this method to determine the source of gems for purely economic reasons is ludicrous. At least for myself, whether an emerald originated in Austria or Columbia would be of less importance than its intrinsic beauty. And from experience managing a jewelry store, I can state that most of my customers would react the same way.

RuthAnn Nichols Champaign, Ill.

A big problem

It would have been helpful to mention in "Tests may better detect prostate cancer" (SN: 4/8/00, p. 228) that the free-PSA-ratio test is effective only for men with a prostate volume less than 40 cubic centimeters. The test doesn't work for men with larger prostates. This is because, for larger prostates, the ratio of free to total PSA is elevated to roughly the same level in men with cancer and those with benign prostate hyperplasia but no cancer.

Robert Oglesby Rochester Hills, Mich.

Researcher Peter H. Gann of Northwestern University Medical School in Chicago agrees that prostate volume should be taken into consideration by physicians diagnosing prostate ailments. He cautions, however, that no cutoff, such as 40 cubic centimeters, has been established as the point beyond which the free-PSA-ratio test doesn't work. He also notes that prostate volume is difficult to ascertain.

--N. Seppa

A concern for cause

Sanity and dementia aren't so much discrete states as poles of a continuum ("Pushing the mood swings," SN: 4/8/00, p. 232). It seems to me that slightly irrational (perhaps inappropriate is a better word) behavior would tend to make other people avoid you. And as you tend to do less well in social interactions, you would tend to avoid them. Perhaps dementia causes isolation. Or there's a positive feedback loop, where increasing dementia causes increasing isolation, which prompts increasing dementia.... One thing is sure, though, a simple correlation doesn't prove causation either way.

David Reed Smith Hampstead, Md.

Trial on trial

I cannot believe that a clinical trial of a new drug in a field in which there are accepted beneficial therapies ("Placebos for depression attract scrutiny," SN: 4/29/00, p. 278) would be either proposed as ethical by physicians or accepted by the Food and Drug Administration when containing a control group deprived of that beneficial treatment.

For prior approval of the existing beneficial treatment, there must have been a comparison with prior therapies, leading ultimately to controlled comparisons with placebos or no treatment. To redo those comparative analyses is to reinvent the wheel--at the great expense of those volunteers who were deprived of the current best treatment and at the expense of the investigation. This is at once bad science, abysmal ethics, and wasteful economics.

McClellan G. Blair Indiana, Pa.