'---___ -'1 CORRESPONDENCE

SUMMARY STATISTICS AND TREATMENT DECISIONS To the Editor: As a former student of Dr. Fein­stein, I was interested in the study by Forrow et al [1] and the accompanying editorial [2]. Al­though I also suspect that many who read the medical literature still equate significant differ­ences and statistically significant differences, I was somewhat dis­appointed by both Feinstein's and Forrow et al's analyses.

Ironically, my first concern stems from an example of the very problem addressed by For­row et al. Feinstein's summary of the study's results suggests that "most clinicians seem unaware" of the lack of a difference be­tween the same results presented in different ways when in fact the majority (54%) were not swayed by the different summaries. An editorial dealing with a study en­titled "Absolutely Relative: How Research Results Are Summa­rized Can Affect Treatment De­cisions" is certainly not the opti­mal forum for decrying a glass mostly empty when it is actually more than half full.

More important, however, is the absence of a critical appraisal of the study. For example, al­though 46% of the respondents failed to give the same response to both summaries, this propor­tion may be misleadingly large given that subjects indicated their responses on a scale con­taining seven choices. Thus, clini­cians who felt more (or less) likely to treat after reading a summary had three choices of how much more (or less) likely they were in­clined. This suggests that the proportion who appeared to change their treatment decision would be a great deal smaller if the results were reanalyzed after equating the three degrees of more (or less) likely to treat. In the absence of such an analysis, it is not clear how often differences

in how results are summarized af­fect treatment decisions.

FREDERICK R. ARONSON, M.D., M.P.H.

University of California, San Francisco

San Francisco, California

1. Forrow L, Taylor we, Arnold RM. Absolutely rela­tive: how research results are summarized can af· fect treatment decisions. Am J Med 1992; 92: 121-4. 2. Feinstetn AR. Invidious comparisons and unmet dinical challenges. Am J Med 1992; 92: 117-20.

Submitted April 13, 1992, and accepted September 8, 1992

The Reply: Dr. Aronson says he is a "former student," but I hope someone else taught him how to miss the main point of a discussion. Yes, I agree that 46% is not a majority; and yes, the exact percentages may have been affected by nu­ances of the rating scales-but these minor numerical variations are unimportant. As Forrow et al have indicated, if an altered mode of quantitative expression "can even occasionally affect" a physician's clinical judgment, the appropriate use of summary sta­tistics should receive "scrupulous attention."

Because such attention is not given either in medical education or in contemporary obsessions with p values and confidence in­tervals, I hope Dr. Aronson will direct his pedantic energy toward improving the basic defect, rath­er than minimizing estimates of its prevalence.

AL VAN R. FEINSTEIN, M.D. Yale University School of Medicine

New Haven, Connecticut

The Reply: The most important finding in our study was not simply that 46% of respondents gave differ­ent responses when the same re­sults were presented in different ways. In fact, 89% of those who gave different responses indicat­ed a greater inclination to pro­vide treatment when presented with the relative reductions (24% and 20.3%) in endpoints than

when presented with the absolute reductions (0.4% and 1.5%). Dr. Aronson is correct that, as we ex­plicitly stated in our article, one cannot conclude from this how often differences in how results are summarized may alter treat­ment decisions. Nonetheless, there can be little question that these differences in interpreta­tion do occur. In the case of the relative and absolute risk reduc­tions found in the highly influen­tial trials of the Medical Re­search Council and the Hyper­tension Detection and Follow-up Program, a presentation of the relative risk reduction clearly leads to a greater likelihood of treatment.

LACHLAN FORROW, M.D. Beth Israel Hospital

Boston, Massachusetts

PRIMARY ANTIPHOSPHOLIPID SYNDROME To the Editor: The Brief Clinical Observation of Lecerf et al [1] confirming our earlier findings of a role for anti­phospholipid antibodies in some patients with thrombotic arterial occlusions [2] requires some com­ment.

Our original criteria for the di­agnosis of a "primary" antiphos­pholipid syndrome were first published in December 1988 [3] followed in 1989 by our definitive publication of 70 patients con­firming these criteria [4]. Alar­con-Segovia and Sanchez-Guer­rero [5] published their series of nine patients in 1989 suggesting that hemolytic anemia, leg ulcers, and livedo reticularis might con­stitute criteria for diagnosis of the condition. We do not include these manifestations as major features for the diagnosis of a "primary" syndrome, but rather as minor, occasional accompani­ments only. It is possible that leg

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