Accuracy of blood pressure monitors used for BP checks in retail pharmacies
Hodgkinson J., McManus R., Koshiaris C., Martin U., Mant J., Heneghan C., Hobbs FDR.
Background Free blood pressure (BP) checks offered by community pharmacies offer a potentially useful opportunity to diagnose and/or manage hypertension, but the accuracy of the sphygmomanometers in use is currently unknown. Aim To assess the accuracy of validated automatic BP monitors used for BP checks in a UK retail pharmacy chain. Design and Setting 52 pharmacies from one chain were visited in a range of locations (inner city, suburban, rural) in central England. Method Monitor accuracy was compared to a calibrated reference device (Omron PA-350), at 50 mmHg intervals across the range 0-300 mmHg (static pressure test), with a difference from the reference monitor of +/-3 mmHg at any interval considered a failure. The results were analysed by usage rates and length of time in service. Results Eight (13%) monitors failed (i.e. were more than 3mmHg from reference), all underestimating BP. Monitor failure rate from the reference monitor of +/- 3 mmHg at any testing interval varied by length of time in use (2/38, 5% before 18 months vs. 4/14, 29% after 18 months; p=0.038) and to some extent but non-significantly by usage rates (4/22, 18% in monitors used more than once daily vs. 2/33, 6% in those used less frequently; p=0.204). Conclusion BP monitors within a pharmacy setting fail at similar rates to those in general practice. Annual calibration checks for blood pressure monitors are needed, even for new monitors, since these data indicate declining performance from 18 months onwards.