Letters to the Editor Interleukin-1 Concentrations in Patients Infected with Human Immunodeficiency Virus However, we realized that the data for some of the groups were skewed. As suggested by Dr. Leeming, we reanalyzed interleukin-1 alpha and beta data using the Mann-Whitney U test, a nonparametric test. The mean values for all the groups and the P values obtained by the Mann-Whitney U test are given in Table 1. As shown, utilizing the Mann-Whitney U test, the interleukin-1 alpha concentrations in the sera of human immunodeficiency virus (HIV)-seropositive intravenous drug abusers and HIV-seronegative and HIV-seropositive homosexuals were not significantly different from control values. Similarly, the interleukin-1 beta concentrations in the sera of patients with acquired immunodeficiency syndrome were significantly increased over those of the controls. Interleukin-1 beta concentrations in HIV-seropositive asymptomatic homosexuals were significantly decreased compared with concentrations in the controls. The main thrust of our report remains unchanged, in that both HIV-seronegative and HIV-seropositive subjects had much higher concentrations of interleukin-1 alpha than interleukin-1 beta in their bloodstreams. I thank Ray Gertz and Edith Flaster for their help in statistical analysis.

The interesting article by Reddy and Grieco (M. M. Reddy and M. H. Grieco, J. Clin. Microbiol. 27:1919-1923, 1989) is marred by improper use of statistics. The use of the Student t test for data which are so obviously skewed obscures some of the main points. Upon cursory examination, it appears in Fig. 2 that the interleukin-1 alpha concentrations in asymptomatic intravenous drug abusers who are human immunodeficiency virus (HIV) negative are much higher than the concentrations in normal controls. On the other hand, the HIV-negative asymptomatic homosexuals would give values close to if not greater than those of normal controls if nonparametric statistics were applied. The same observation applies to both asymptomatic intravenous drug-abusing, HIV-positive patients and asymptomatic homosexuals who are HIV positive. On the other hand, the lymphadenopathy syndrome HIV-positive patients and those with clinical acquired immunodeficiency syndrome may have concentrations above those of the controls. R. J. Leeming Department of Haematology

The General Hospital Steelhouse Lane Birmingham B4 6NH England

Mohan M. Reddy R.A. Cooke Institute of Allergy St. Luke'slRoosevelt Hospital Center 428 West 59th Street New York, New York 10019

Author's Reply We used the Student t test, which is generally considered to be a robust and reasonable test, for most of our data.

TABLE 1. Interleukin-1 concentrations and P values for various groups of subjects Group (no. of subjects)

Normal controls (26) Asymptomatic intravenous drug abusers 60 44

Asymptomatic homosexuals 40 40

Lymphadenopathy (70) Acquired immunodeficiency syndrome (89)

Mean interleukin-1 concn

HIV

antibody

Alpha

(pg/ml) ±

SE (P)

Beta

Negative

359 ± 146

4.04 ± 1.4

Negative Positive

581 ± 44 (