The forearm measure overestimated systolic ( mean difference 2.2 mmHg , 95 % limits of agreement 19 mmHg ) , diastolic ( mean difference 3.4 mmHg , 95 % limits of agreement 14.4 mmHg ) , and mean arterial pressures ( mean difference 4.1 mmHg , 95 % limits of agreement 13.7 mmHg ) .