“…[1][2][3][4][5][6][7][8][9][10][11] However, many of these studies are limited by methodological problems, such as limited sample size, [2][3][4][5]8,9 assessment of limited outcomes, 3,7,8,11 suboptimal adjustment for important demographic confounders, 2,3,6,8,10,11 not being population based, 2,4,8,10 inadequate or poorly defined comparison groups, 2,4 and possible differences between groups regarding health care access. 2,8 Kaiser Permanente is an integrated health care system whose members have prepaid access to medical care and no formal barrier to specialist management. Kaiser Permanente uses a comprehensive patient survey to assess asthma outcomes and can also link these results to administrative medical utilization data.…”