[Combined uni- and multicenter double-blind studies in hypertensive patients. Comparison of blood pressure...

In a double-blind study to investigate the antihypertensive effect of a fixed triple combination with 0.05 mg reserpine, 2.5 mg clopamide and 0.4 mg dihydroergocristine in comparison to a fixed double combination with 0.05 mg reserpine and 2.5 mg clopamide, a patient subgroup of 34 patients followed a unicenter (central unit, 'institute') as well as a multicenter (established physicians) study design. The patients visited both investigation units on the day of admission to the study (week 0), after four weeks and after eight weeks of therapy (after the morning intake of the drugs). The paper in hand looks at the results of this subgroup with respect to the conformity of blood pressure values in the two investigative units. The analyses confirm the already published results of the entire study: Both combinations proved to be highly effective antihypertensive drugs. The triple combination showed therapeutical advantages for systolic blood pressure after four weeks, for diastolic pressure after eight weeks of therapy at the 'institute' as well as, although less distinct, in the medical offices. A comparison of the individual values did not show a convincing coherence of the measurements between institute and offices. All investigated possible systematic sources of error (different methods of measurement, days or times of measurement) could be excluded by correlation statistics as a reason for the divergences. The results show the necessity--particularly in multicenter studies--of a careful documentation of all accompanying data (e.g. method or time of measurement) as well as a greatest possible standardization of investigation (e.g. identical measuring apparatus and investigator.)