The Microlife 3AC1: an accurate blood pressure measurement device in pregnancy and pre-eclampsia

As one of the most commonly performed screening tests in pregnancy, accurate blood pressure measurement is vitally important to the diagnosis and management of hypertensive disorders in pregnancy. Few automated devices have been assessed for their accuracy in this population according to a recognised protocol. None of the devices, which achieved sufficient accuracy in pregnancy, were accurate in pre-eclampsia, except for one (device for self-measurement). We assessed the accuracy of the Microlife 3AC1 in a pregnant population, including pre-eclampsia, according to the protocol of British Hypertension Society. 

Forty-five pregnant women were recruited from the antenatal wards and clinics at a large teaching hospital. Sixteen of these women were pre-eclamptic according to the definition of the International Society for the Study of Hypertension in Pregnancy. Nine sequential same arm blood pressure measurements were taken by two trained observers, alternating between a mercury sphygmomanometer and the device. Data was analysed according to the guidelines of the British Hypertension Society protocol. An A or B grade is required for both systolic and diastolic pressures to pass the protocol. 

The Microlife 3AC1 achieved the highest possible grade for accuracy in pregnancy (A/A) and also passed in pre-eclampsia by achieving A/B grade for systolic and diastolic pressure respectively. It also met the standard required by the Association for the Advancement of Medical Instrumentation (AAMI) by achieving a mean difference <5mmHg (SD <8mmHg) for both pregnancy and pre-eclampsia for systolic & diastolic pressures respectively [pregnancy -0.4(5.2) & -1.1(5.9); pre-eclampsia -1.1(7.1) & -3.7(4.1)]. 

The Microlife 3AC1 can be recommended for use in a pregnant population according to the BHS protocol. It is one of only two devices shown to be accurate in pregnancy, including women with pre-eclampsia. 

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