Should the corticosteroid to bronchodilator ratio be promoted as a qualityprescribing marker?

In recent years the ratio of inhaled corticosteroid: bronchodilator (C:B) p rescribing has been promoted as a quality marker for asthma treatment and c ross-sectional data indicate an association with hospital admissions. If pr escribing advice has been followed then it can be hypothesised that the C:B ratio will have increased and hospitalisation decreased. The West Midlands General Practice Research Database was used to monitor changes in the C:B ratio and hospital referrals for asthma between 1993 and 1996. The C:B rati o increased from 0.5 to 0.6 (P < 0.001) and hospital referrals decreased fr om 7% to 4% per annum (P < 0.001). Overall, 38% of the variation in hospita l referrals was explained by the C:B ratio. This is higher than previous st udies, perhaps because the, study was longitudinal and the ratio assessed a ccurately in terms of volume rather than prescription items. When measured in defined daily doses, the C:B ratio does appear to have validity as an in dicator of good prescribing in primary care. The General Practice Research Database offers an opportunity for assessing the validity of prescribing in dicators before they are considered for wider use by Primary Care Groups an d Health Authorities.