Question special

Thank you to all of the authors, faculty and residents who make this journal club possible.

While procalcitonin levels did not reduce overall antibiotic use, the intriguing data in Figure S3 seems to suggest that it did affect antibiotic use for a subset of patients. Figure S3 shows that antibiotic use was similar (50.7% vs 52.2%) between the second and third procalcitonin-level tier in the usual care arm. However, when clinicians had knowledge of the procalcitonin level, the antibiotic use is quite different (28.6% vs 74.1%). This suggests that procalcitonin helped clinicians reclassify patients in these tiers in terms of need for antibiotic therapy. Perhaps the second and third tier represent patients in whom clinicians have more uncertainty. The provision of procalcitonin and national antibiotic guidelines may have more influence in this subgroup.

It is also interesting that antibiotic use was similar between both study arms at PCT <0.1 and at PCT >0.5. Perhaps at these extremes of procalcitonin, clinicians already had sufficient alternative data to decide on antibiotic therapy.

In the procalcitonin arm, the decreased antibiotic use in the second procalcitonin-level tier is partly negated by the increased antibiotic use in the third tier. Overall antibiotic-days are similar between study arms but antibiotics may have been used more appropriately when clinicians knew the procalcitonin level.

I am curious what impressions others have from this data.