LAUSR

We read interest the article published recently in this Journal by Llewelyn et al . 1 which provides an additional piece of evidence that procalcitonin (PCT) plays an important role in antimicrobial stewardship of COVID-19 patients. Besides the interrupted time series analysis, both the similarity of time series curves between PCT adopters and always users, and the dissimi-larity between PCT users and never users, provide further evidence that PCT is driving usage of antibiotics in these hospitals. Our controlled study previously demonstrated that combining molecular tests in emergency departments with PCT could de-crease the duration of intravenous antibiotics and hospital stays, and increase the percentage of antibiotic de-escalation. 2 The bene fi t of PCT in antimicrobial stewardship may have been un-derestimated if antibiotic de-escalation was not analysed as a major outcome. One additional potential bias that merits discus-sion concerns the balance of patients ’ illness severity between PCT-adopting and non-adopting hospitals. It has been