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Abstract

The use of a set of new end points obtained from ambulatory lood pressure (BP) monitoring in addition to the BP values themselves has been advocated to improve sensitivity and specificity in the diagnosis of hypertension and the evaluation of a patient's response to treatment. Among these parameters, it has been suggested the use of a BP load, percentage of values above a given constant reference limit or computed by reference to daytime and nighttime limits. We examined the effectiveness of this parameter as a potential screening test for the detection of hypertension in pregnancy. We analyzed 2421 BP series sampled from 234 normotensive pregnant women and 167 women who developed gestational hypertension or preeclampsia (gestational hypertension and proteinuria, >300 mg/24 hours in urine). BP was measured every 20 minutes during the day and every 30 minutes during the night for 48 hours with an ambulatory device once every 4 weeks from the first visit to the hospital (usually before 14 weeks of gestation) until delivery. The BP load was obtained as the percentage of values >140/110/90 mmHg in systolic/mean arterial/diastolic BP during active hours, or 120/95/80 mmHg during resting hours, as well as by comparison with limits obtained by progressively reducing the previous limits by 5 mmHg, up to a final threshold of 125/95/75 (day) and 105/80/65 (night). Sensitivity for the BP load computed by reference to the highest limits used here is <55% in all trimesters of pregnancy. Specificity was always <69%. The best results were obtained when 130/100/80 (day) and 110/85/70 (night) were used as reference in the 3rd trimester, and when the lowest tested limits of 125/95/75 and 105/80/65 were used as reference in the 1st and 2nd trimesters (sensitivity always >74%). However, a small increase in the threshold value of BP load used for diagnosis results in a large decrease in sensitivity. This result characterizes an unstable and thus poor diagnostic test. The optimum reference limits for computing the BP load, markedly below 140/90 mmHg, must be defined as a function of gestational age, in keeping with the predictable trends in BP along pregnancy previously documented [Ayala et al. Hypertension. 1997;30:611-8].

Pregnancy, Blood Pressure load, Preclampsia
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© American Journal of Hypertension, Ltd. 2001
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