Measuring broad-spectrum antibiotic use in hospitals with established versus new indicators

The target of a 30 % reduction in the use of broad-spectrum antibiotics in hospitals from 2012 to 2020 was not achieved, measured using the standard indicator of defined daily doses (DDD) per 100 bed days. We wished to investigate the reliability of the standard indicator and of selected alternative indicators for antibiotic use, and to determine the actual reduction in use.

We included ten DDD-based indicators with adjustment for combinations of activity marker, admission category (inpatient vs. all admissions), and case mix, and evaluated these according to how each indicator correlated with antibiotic resistance in a self-developed model. We then calculated use of broad-spectrum antibiotics in hospitals for the period 2012-20 with indicators deemed valid, and compared these indicators with regard to change in use and ranking of hospitals according to use. We used consumption rate (DDD per 1000 inhabitants per day) as an activity-neutral reference indicator (national and regional).

All the indicators for antibiotic use showed a strong correlation with resistance. For five indicators the correlation was statistically significant. Of these, the indicator that combined adjustment for the total number of admitted patients and case mix accorded best with the consumption rate (35.6 %). The same indicator also showed the largest reduction in use (29.3 %) and gave the most hospitals that achieved a reduction of at least 30 % (13 of 22).

Combined adjustment for number of admitted patients and case mix represents a new, robust indicator for antibiotic use that is suitable for hospitals at all levels. The indicator can be used in parallel with the consumption rate, and consideration should be given to introducing the latter as the new standard indicator at national and regional level.