Table 3.

Formulae to calculate the systolic blood pressure threshold from diastolic blood pressure using morning and evening readings during the sampling period

	1 day	2 days	3 days	4 days	5 days	6 days	7 days
90% PPV	340.0 – 2.2 x DBP	391.1 – 3.2 x DBP	430.3 – 3.7 x DBP	505.9 – 4.7 x DBP	483.9 – 4.5 x DBP	476.7 – 4.4 x DBP	504.9 – 4.8 x DBP
90% NPV	287.4 – 2.2 x DBP	363.2 – 3.2 x DBP	413.4 – 3.7 x DBP	491.0 – 4.7 x DBP	479.4 – 4.5 x DBP	473.0 – 4.4 x DBP	499.9 – 4.8 x DBP
95% PPV	345.5 – 2.2 x DBP	407.9 – 3.2 x DBP	443.5 – 3.7 x DBP	519.1 – 4.7 x DBP	497.7 – 4.5 x DBP	492.0 – 4.4 x DBP	517.1 – 4.8 x DBP
95% NPV	274.2 – 2.2 x DBP	355.5 – 3.2 x DBP	402.9 – 3.7 x DBP	480.0 – 4.7 x DBP	470.0 – 4.5 x DBP	465.7 – 4.4 x DBP	492.2 – 4.8 x DBP

These formulae can be used to determine if an individual’s BP is in region A, B, or C. For example, a person with SBP/DBP of 170/85 mm Hg after one day of HBPM (Day 1), would be in region A (using a 90% PPV threshold) since the person’s SBP (170 mm Hg) is greater than the calculated SBP of 153.0 mm Hg based on the individual’s DBP of 85 mm Hg. Another person with SBP/DBP of 122/70 mm Hg after one day of HBPM (Day 1), would be in region B (using a 90% NPV threshold) since the person’s SBP (122 mm Hg) is less than the calculated SBP of 133.4 mm Hg based on the individual’s DBP of 70 mm Hg. By definition, a person not in region A or region B is in region C.

NPV: negative predictive value, PPV: positive predictive value, SBP: systolic blood pressure, DBP: diastolic blood pressure