Re: predictors and microbiology of respiratory and bloodstream infection in patients with COVID-19.

To the Editor,

We read the latest systematic review and meta-analysis by Langford et al. with great interest [1]. The authors provide a high-quality review concerning the incidence and microbiological predictors of respiratory and bloodstream bacterial infections in COVID-19 patients. Among other exclusion criteria, they chose to exclude editorials and letters, studies in which bacterial infection was only presumed or suspected, and studies in which serology was used as a bacterial infection diagnostic approach. Based on those criteria, it is unclear why certain references were included in their final analysis. First, two studies were, in our opinion, inappropriately included in the category of ‘bacterial co-infection’. The first study by Di Nisio et al. exclusively describes viral co-infection rates and rates of Mycoplasma spp. co-infection [2]. Because it is unclear if the diagnosis of Mycoplasma spp. infections was based on serological testing, we would exclude this study. The second study by Ferguson et al. did not microbiologically define the diagnosis of ventilator-associated pneumonia. Because viral and fungal co-infections might have been included in Langford's analysis of bacterial co-infection rates, we would also exclude this study [3]. Second, an observational study by Karaba et al., including 1016 patients, accurately described bacterial co-infection rates. However, Langford et al. categorized those infections as ‘co-infection’ instead of ‘bacterial co-infection’, possibly leading to an underestimation of bacterial co-infections [4]. Third, a letter to the editor was included in the meta-analysis, despite the exclusion criteria [5].

To guarantee the reproducibility of this meta-analysis, we also think that including the final search strategy in the Supplementary Material section would be of added value. Moreover, the forest plots that were used to determine the bacterial co-/superinfection rates should display every included study, separately for co-infections and secondary infections.

Transparency declaration

Johan Van Laethem and Sabine D. Allard have no conflicts of interest to declare. No funding was received.