Ideally antibiotic therapy should decrease (de-escalate) as broad-spectrum antibiotics are replaced by antibiotics with narrower spectrum befitting the pathogen(s) identified. De-escalation is considered an important goal of antibiotic stewardship.
Antibiotic spectrum: Igles et al used a modified ASI (antibiotic spectrum index)
Spectrum score: sum of ASI's for antibiotics given in a single day
Reports of de-esclation have focused on treatment of pneumonia, but the concept applies to other infections.
Parameters used by Igles et al:
(1) spectrum score based on all antibiotics received on day 1 (day 0 is day diagnosis made)
(2) spectrum score based on all antibiotics received on day 3
Bohan refers to comparing antibiotic use on day 2 of hospitalization (day after admission to a hospital which would be the day of diagnosis) vs use on day 4 (aka day 3 for Igles et al).
difference in spectrum score =
= (spectrum score on day 1) - (spectrum score on day 3)
Interpretation:
• minimum difference: negative number (higher spectrum score on day 3)
• maximum difference: positive number
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Difference Score
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Interpretation
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negative
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escalation
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0
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unchanged
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positive
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de-escalation
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