EFFECTS OF SUPINE BLOOD-PRESSURE ON INTERPRETATION OF STANDING UP TEST IN 500 PATIENTS WITH DIABETES-MELLITUS

The relationship between fall in blood pressure (BP) on standing and s upine BP before standing up was studied in 75 healthy controls and in 500 patients with diabetes mellitus (DM) using conventional BP measure ments. The influences of physiological (sex, age, height) and DM-relat ed factors (type, duration, HbA(1c)-level, use of insulin, oral antidi abetic and anti-hypertensive medication) on BP-fall were assessed. The effects of using a fixed abnormality threshold and a new supine BP-re lated abnormality definition on interpretation of the test were determ ined. Highly significant relationships of BP-fall with supine BP were found in control and DM subjects. Slopes did not differ between these groups. Slopes for systolic BP-fall were steeper in type 1 than in typ e 2 DM patients. A forward stepwise regression procedure revealed that supine BP (explaining 24% of variance) and HbA(1c) (explaining 1%) ha d significant influences on systolic BP-fall. Diastolic supine BP expl ained 14% of diastolic BP-fall, age 3%, and sex 2%. Only supine BP was thus of practical relevance in explaining BP-fall. Taking supine BP i nto consideration affected test results: of 74 subjects with an abnorm al conventional systolic BP-fall, 10 (13.5%) had been misclassified ac cording to the new method, and 4 additional patients had been misclass ified as normal. Classification changes were much larger for diastolic BP-fall (63% of conventionally abnormal results were reclassified as normal), but the range of diastolic BP is smaller than for systolic BP , meaning that the measurement error interferes with its clinical util ity. BP-fall was higher in type 2 than in type 1 diabetics, and higher in those using anti-hypertensives than in those who did not. These ef fects were due to differing supine BPs, showing that taking supine BP into account can prevent incorrect conclusions regarding abnormality o f the standing up test in DM. The validity of this test can be improve d by accounting for supine BP.