Of 313 patients whose outpatient parenteral antimicrobial therapy was managed by an ID physician, only 39 [12.5%, 95% CI (8.8%-16.1%)] had clinical decisions influenced by erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), or both. ESR/CRP ordering was associated with 30 in excess cost per treatment course (average duration 5.1 weeks) representing a diagnostic stewardship opportunity.