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Blood pressure and serum creatinine.

To the Editor. —The article by Perneger et al 1 on the effect of increased blood pressure on kidney function supports the conclusion that we reached in a previous study. In our study, 2 "time averaged blood pressures" (clinic blood pressures recorded quarterly for a mean period of approximately 10 years) in a hypertensive group and a normotensive control group predicted change in serum creatinine levels. Several methodological issues are relevant to both studies. First, since hypertension may occur as a consequence of renal damage, it might be more useful to look at blood pressure levels measured prior to a change in renal function (as in the study by Perneger et al) instead of blood pressure levels measured during the follow-up period, as we used. Nevertheless, because of the unreliability of single blood pressure measurements, it may be necessary to obtain several baseline blood pressure values to see their effect