APPROACHES TO THE PROBLEMS OF MEASURING THE INCIDENCE OF STROKE - THEAUCKLAND STROKE STUDY, 1991-1992

Background. Stroke registers are the preferred choice for determining incidence, case-fatality and severity of acute stroke in defined popul ations. This paper highlights some of the problems likely to be encoun tered in this endeavour by describing the experience of measuring acut e stroke prospectively. Methods. The Auckland Stroke Study is a commun ity-based study among 945 000 residents of the Auckland region, New Ze aland. Standard definitions and overlapping case-finding methods were used to identify all new acute stroke events occurring during the 12-m onth period ending 1 March 1992. Particular attention was directed at including nonfatal strokes managed outside hospital. The latter were i dentified by use of a cluster sample, a technique suitable for populat ions where residents have a personal primary health care physician. Re sults. The comprehensive sources of referral to the study involved the review of 5736 records, less than one-third of which met the criteria for inclusion. The majority of included acute stroke events (n = 1803 ) were found through routinely available sources such as hospital admi ssion records (63%) and death registrations (10%). The remainder (27%) were identified through intensive efforts at case-finding of stroke e vents managed outside hospital. The 1803 events were registered in 176 1 people, 817 men and 944 women; for 587 (72%) men and 718 (76%) women , the stroke was the first ever experienced. Conclusions. While time-c onsuming, costly and,demanding, there appears to be no easier alternat ive to a register to estimate incidence. This study demonstrates the i mportance of the use of comprehensive case-finding sources and suggest s approaches to overcoming the difficulties in monitoring stroke incid ence in large populations.