Lack of up-to-date studies and data conversion may lead to biased results

I am writing this letter in reference to a recent study published in Critical Care entitled “Incidence, risk factors and outcomes of nosocomial infection in adult patients supported by extracorporeal membrane oxygenation: a systematic review and meta-analysis” [1]. I would like to commend the authors for their comprehensive and in-depth study of this important topic. This systematic review and meta-analysis undoubtedly provides valuable insights into our understanding of the incidence, risk factors, and prognosis of nosocomial infection in extracorporeal membrane oxygenation (ECMO) patients. However, two issues require further consideration.

First, we note that the literature search deadline for this study was November 1, 2022, which may have resulted in missing some important data, especially given the significant increase in ECMO use in recent years and the impact of the COVID-19 pandemic. Several studies have been published so far at the end of 2022 that may have a significant impact on the conclusions of this article. For example, the retrospective study by Barbaro et al. [2] published in the Lancet, which included 4,812 patients with COVID-19 treated with ECMO at 349 medical centers worldwide in 2020, reported Bloodstream infection (733/4,812) and Urinary tract infection (335/4,812) incidence. In addition, Nesseler et al. [3] reported the incidence of healthcare-associated infections in patients with severe COVID-19 treated with ECMO and assessed the impact of nosocomial infections on mortality, finding that ECMO-associated nosocomial infections were not associated with hospital death (hazard ratio = 1.00; 95% confidence interval: 0.79–1.26; P = 0.986). Considering the rapid development of ECMO technology, the authors should consider updating their analysis, especially for studies related to COVID-19. This would make the review more comprehensive and provide up-to-date guidance for clinical practice.

Second, I note that the authors did not consider data conversion when performing meta-analysis of the prevalence of nosocomial infection, which may affect the accuracy and reliability of the results. Data transformation is an important methodological consideration when performing meta-analysis of proportions. Untransformed raw proportion data often do not conform to normal distribution assumptions and may lead to inaccurate confidence interval estimates. Commonly used transformation methods include logit transformation and Freeman-Tukey double arcsine transformation [4], which stabilize the variance and bring the data closer to a normal distribution, thereby improving the accuracy of meta-analysis [5]. Based on the data extracted by Ait Hssain et al. [1], we used the above two transformations separately to obtain different results (Fig. 1). Different summary estimates and confidence intervals may affect evaluation of the overall incidence of nosocomial infection in ECMO patients, which in turn affects clinical decision making. I recommend that the authors consider performing a sensitivity analysis to compare the results of converted and unconverted data. If there is a significant difference in results, this should be discussed in the article and its potential impact on conclusions should be explained.

Despite these limitations, the study provides valuable insights. We look forward to seeing further research and discussion on this important topic.

Fig. 1

Forest plot for a pooled incidence nosocomial infection per 1000 ECMO-day based on Freeman-Tukey double arcsine transformation; b based on logit transformation

Full size image

No datasets were generated or analysed during the current study.

1. Ait Hssain A, Vahedian-Azimi A, Ibrahim AS, et al. Incidence, risk factors and outcomes of nosocomial infection in adult patients supported by extracorporeal membrane oxygenation: a systematic review and meta-analysis. Crit Care. 2024;28(1):158.

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2. Barbaro RP, MacLaren G, Boonstra PS, et al. Extracorporeal life support organization. Extracorporeal membrane oxygenation for COVID-19: evolving outcomes from the international extracorporeal life support organization registry. Lancet. 2021;398(10307):1230–8.

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3. Nesseler N, Mansour A, Schmidt M, et al. ECMOSARS investigators; SFAR Research Network. Healthcare-associated infections in patients with severe COVID-19 supported with extracorporeal membrane oxygenation: a nationwide cohort study. Crit Care. 2024;28(1):54.

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4. Chen Y, Chen D, Wang Y, et al. Using Freeman-Tukey double arcsine transformation in meta-analysis of single proportions. Aesthet Plast Surg. 2023;47(Suppl 1):83–4.

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5. Lin L, Chu H. Meta-analysis of proportions using generalized linear mixed models. Epidemiology. 2020;31(5):713–7.

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Author notes

1. Guoying Wang and Fen Liu are co-first author.

Authors and Affiliations

1. Department of Critical Care Medicine, The Second People’s Hospital of Dongying, Dongying, Shandong, China

   Guoying Wang

2. Department of Critical Care Medicine, The First Affiliated Hospital of Shandong First Medical University & Shandong Provincial Qianfoshan Hospital, Jinan, Shandong, China

   Fen Liu

3. Respiratory and Critical Care, Qingdao Hongdao People’s Hospital, Qingdao, Shandong, China

   Linqing Xu

4. Department of Research, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong, China

   Xiaoming Zhou

5. Department of Pharmacy, Dongying People’s Hospital, Dongying, Shandong, China

   Xiaoming Zhou

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Guoying Wang, Fen Liu, and Linqing Xu wrote the main manuscript text. Xiaoming Zhou reviewed, and all authors contributed to the final manuscript.

Corresponding author

Correspondence to Xiaoming Zhou.

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Wang, G., Liu, F., Xu, L. et al. Lack of up-to-date studies and data conversion may lead to biased results. Crit Care 28, 347 (2024). https://doi.org/10.1186/s13054-024-05109-5

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• Received: 21 September 2024

• Accepted: 23 September 2024

• Published: 28 October 2024

• DOI: https://doi.org/10.1186/s13054-024-05109-5

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