Incidental blood pressure elevations: a MIRNET project. BACKGROUND. A prospective study was undertaken to determine the prevalence of hypertension in office patients with an incidental diastolic blood pressure greater than or equal to 90 mm Hg. METHODS. During routine screening of 14,890 patients, 174 patients with elevated diastolic blood pressures but no previous diagnosis of hypertension were identified over a 3-month period. Only 115 (64%) returned as requested for two subsequent blood pressure readings. RESULTS. Sixty percent of those returning fit the definition for hypertension using the criteria of the Joint National Committee on Detection, Evaluation, and Treatment of Hypertension. Sixty-nine percent (43/62) of the men and 49% (26/53) of the women were hypertensive. Women under 40 years old were less likely to be hypertensive, but age did not predict hypertension in men. Among those patients with a diastolic pressure reading below 105 mm Hg, progressively higher diastolic readings on the first visit did not predict a higher probability of hypertension. Among those patients with a diastolic pressure reading above 105 mm Hg, however, 90% (9/10) were hypertensive. CONCLUSIONS. Physicians should take incidental elevation of diastolic pressure seriously because of the high prevalence of confirmed hypertension in this group of patients. 