We are chasing an illusory BP target
Many of the performance indicators in the new contract relating to blood pressure specify a reading of 150/90mmHg obtained from patients within the last nine months. Blood pressure is a variable, fluctuating within a fairly wide range of values from hour to hour.
Any competent scientist would argue there is a huge amount of noise in the planned system of data collection relating to blood pressure. This includes: when the patient takes their medication or has their BP measured; the white coat effect; if two readings are taken, which one is used; the arm used (BP varies by up to 10 points from arm to arm); the machine's calibration; the influence of caffeine; the length of time they have had to wait.
GPs are to be paid for performance based on a chosen value of 150/90mmHg. As the data year progresses, a GP might be forgiven for mentally adjusting a given BP figure downwards to allow for what they might perceive as a white coat effect at the time of the reading.
This tendency might reasonably increase when the data manager informs them the practice is likely to fail at target X because N per cent of patients are over target.
Progressive clinicians in the US are increasingly advocating BP lowering as a key concept in preventive medicine, with suggested values of 140/70mmHg or less.
As we in the UK struggle to achieve 150/90mmHg we may pause to reflect that we are chasing an illusion created by politicians and in the process will be supplying data that is scientifically useless, so full of variables that the scientific mind gasps in disbelief.
Dr Nicholas Down