Data analysis
A meta-analysis was conducted to examine the mortality incidence in
venovenous ECMO treatment for COVID 19. Data were summarized using the
risk ratio (95% confidence interval (CI)). The data were pooled using
DerSimonian-Laird random effects model (16). P value of
0.05 or less was statistically significant. Cochran Q and I2 were used
to assess heterogeneity between studies. The degree of heterogeneity was
categorized as either low (I2 < 25%), moderate (I2 =
25%–75%), or high (I2 > 75%) (17). A P
value of ≤ 0.05 indicated significant heterogeneity. A subgroup
meta-analysis according to the study’s country of origin was conducted
to investigate the high heterogeneity detected. Exploratory
meta-regression analysis was performed to identify significant
moderators using the inverse-variance weighted-least-squares linear
regression analysis. Studies that included a control group with patients
treated with mechanical ventilation were independently studied and
mortality estimates were pooled using odds ratio and 95% CI. Secondary
outcome measures included age, ventilation days before ECMO, and
duration time on ECMO. Publication bias was examined by visual
inspection of the funnel plot and tested by Egger’s test and Begg and
Mazumdar test. A P value of ≤ 0.05 indicated the existence of
publication bias. All analyses were performed using Open Meta Analyst
software Windows 10 version.
The data used in the meta-analysis in each study were the number of
mortality events and the number of closed cases (either cured or dead).
Patients who were still on treatment were not included in the final
analysis of cases of the study. The corresponding authors of the studies
were contacted by email to provide additional information regarding the
patients who were still receiving treatment. The numbers used in Jacobs
et al (2020) and Beyls et al (2020) were not those reported by the study
but rather provided by the author (unpublished data).
Trial was registered with PROSPERO at
www.crd.yorl.ac.uk/PROSPERO
under registration number
CRD42020183861