HIGH-SENSITIVITY TEST FOR THE EARLY DIAGNOSIS OF GESTATIONAL HYPERTENSION AND PREECLAMPSIA .3. COMPUTATION OF TIME-SPECIFIED TOLERANCE INTERVALS AS REFERENCE FOR BLOOD-PRESSURE EXCESS IN THE DIAGNOSIS OF GESTATIONAL HYPERTENSION

Hardware for automatic long-term measurement of blood pressure is hen used in combination with a set of software modules for the computation of time-specified tolerance intervals and the evaluation of measures of blood pressure excess in the design of a computer-based system for the assessment of gestational hypertension. The variability of blood p ressure, both within any given day (circadian) as well as along pregna ncy, is such that the identification and the proper definition of gest ational hypertension are highly ambiguous when based on single measure ments. A first step to deal with such variability is to replace to con stant limits for blood pressure frequently used in the assessment of g estational hypertension by a time-specified reference interval. For cl inical applications, the use of tolerance intervals has been recommend ed. Accordingly, we have developed a nonparametric method for the comp utation of tolerance intervals for hybrid time series on the basis of bootstrap techniques that, therefore, does nor need to assume normalit y or symmetry in the data. Once such a reference threshold is availabl e, a hyperbaric index, as a measure of blood pressure excess, can be c omputed by numerical integration as the total area (within one cycle) of any given patient's blood pressure above the threshold. We used the method for computation of tolerance intervals to establish time-quali fied reference limits as a function of gestational age for 497 series of blood pressure monitored automatically in 189 women with uncomplica ted pregnancies. This software system for the establishment of time-qu alified tolerance limits and the assessment of the extent and timing o f blood pressure elevation may be helpful in prognosis, diagnosis and treatment with a better asessment of health status, timely treatment l ess harmful, undesired effects, and better monitor of the subject's re sponse to treatment.