DEFINING HYPERTENSION IN OLDER-PEOPLE FROM PRIMARY-CARE CASE NOTES REVIEW

A method of defining blood pressure (BP) status from a review of prima ry care patient records was developed and then validated using the cas e notes of a general practitioner with an interest in hypertension. Da ta were drawn from the records of the previous 6 years of all 65 to 80 -year-old patients in the practice (n = 263). Patients were then categ orised as hypertensive, normotensive or 'undetermined' by using a flow chart based on the mean of the three most recent BP measurements, anti hypertensive medication and comorbidities of ischaemic heart disease, myocardial infarction, angina, oedema or cardiac failure. Mean systoli c BP of greater than or equal to 160 mm Hg and/or diastolic BP of grea ter than or equal to 90 mm Hg were used as a threshold definition of h ypertension and of BP control. Disagreement between general practition er and the notes based definition occurred in 11% of patients (5% hype rtensive, 6% normotensive). Reasons for disagreement were: controlled hypertensives with comorbidities such as angina or heart failure (4%), isolated elevated readings (3%), use of antihypertensive medication f or separate indications (2%), other reasons (2%). The resulting sensit ivity and specificity was 86% and 88% respectively. including the reco rding of a diagnosis of hypertension in the definition increased the s ensitivity to 98% with specificity unchanged at 88%. Actual sensitivit y of the instrument when used in other practices is likely to lie betw een 88% and 98% depending on the quality of the doctor's recording of the diagnosis of hypertension. These findings suggest that data from p rimary care case notes can provide a ready and valid means of defining cases of hypertension for studying the management of hypertension in primary care and for research purposes.