Study design
The COVID-BioB study is an investigation performed at the Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) San Raffaele Scientific Institute, a 1,350-bed university hospital in Milan, Italy. The study was approved by the Hospital Ethics Committee (protocol no. 34/int/2020), was registered on ClinicalTrials.gov (NCT04318366). Full description of patient management and clinical protocols at San Raffaele were previously published [9,10].
Enrolment criteria
After ANGII was obtained from the manufacturer for compassionate use, all patients aged ≥ 18 admitted to an intensive care unit (ICU) with confirmed SARS-CoV-2 infection were consecutively enrolled. Confirmed infection was defined as positive real-time reverse-transcriptase polymerase chain reaction (RT-PCR) from a nasal and/or throat swab together with signs, symptoms, and radiological findings suggestive of COVID-19 pneumonia. Only patients completing their 28-day follow-up were included.
Study intervention and control group
Following delivery of the drug to our ICU, a group of consecutive patients received ANGII (Giapreza®, La Jolla, San Diego, CA, USA) infusion under compassionate use. The drug is approved by both the European Medicines Association and by the US FDA. All patients received ANGII at ICU admission, as vasopressor dose when needing vasopressor therapy or at low dose prophylaxis if vasopressor therapy was not needed. When used as a vasopressor, ANGII was used in addition to norepinephrine, and when used at low dose, there was the possibility to increase the dose if shock developed. All patients received venous thromboembolic events prophylaxis. Patients in the control groups never received ANGII and always received venous thromboembolic events prophylaxis.
The control group was made up of consecutive invasively ventilated patients treated before its introduction in one of several COVID-19 ICUs and consecutive invasively ventilated patients admitted to an adjacent COVID-19 ICU where ANG II was not made available. In both ICUs, patients were under the care of the same team of doctors and nurses who rotated across the various COVID ICUs during the pandemic.
Data collection
Medical records were used for data collection. We obtained data on contact exposure, onset of symptoms and presenting symptoms, medical history and ongoing medications at time of symptoms onset, daily clinical and laboratory data, treatment data, and outcome data. All data were collected by trained investigators independent from the clinical teams. Before analysis, an extensive round of data cleaning was performed by a dedicated data manager, together with clinicians, to check for data accuracy.
Outcomes
All outcomes reported in this study are exploratory in nature and related to the following markers of organ system function:
- Mean arterial pressure and norepinephrine dose for the cardiovascular system
- PaO2/FiO2 ratio for the respiratory system
- Urinary output, serum creatinine, and use of renal replacement therapy for the renal system
- C-Reactive protein level for the inflammatory arm of the immune system
- Lactate for the metabolic system
- Elevated liver enzymes for the hepatic system
- Platelets for the coagulation and bone marrow system
- Clinical thromboembolic complications for the coagulation system
Additional exploratory analyses included the following clinical outcomes:
- The composite of failure to be discharged alive from the ICU at day 28 or death.
- Hospital mortality at day 28
- Duration of mechanical ventilation at day 28
- Hospital length of stay at day 28.
Safety was evaluated by assessment of development of complications until the completion of follow-up (complete definitions of the complications in Online Supplement).
Statistical analysis
A convenience sample was considered for this analysis, with consecutively patients included until the 28 days of follow-up. No missing data for any of the outcomes are present in the dataset, thus, all analyses were complete case analyses without imputation. Continuous variables are presented as medians (quartile 25% - quartile 75%) and categorical variables as number and percentages. Baseline and clinical characteristics of the patients were compared among the groups using Fisher exact tests and Wilcoxon rank-sum tests. Development of complications are presented as unadjusted odds ratios from generalized linear models considering Binomial distribution. Daily data are compared using mixed-effect quantile models accounting for repeated measures, with day as a continuous variable and with day and group (and an interaction among them) as fixed effect. Quantile models considered a = 0.50 and an asymmetric Laplace distribution. P values were extracted after 1,000 bootstrap samplings. Overall p values from this analysis represent the overall difference among groups over time and p values from interaction represent a statistical assessment of whether the trend over time differed among the groups.
Primary and key secondary outcomes were explored and assessed using a Bayesian perspective. The analysis of key outcomes was done using a Bayesian model considering a Bernoulli distribution or using a Bayesian Cox proportional hazard model as appropriate. All models were developed using a Markov Chain Monte Carlo simulation with four chains, and considered a burn–in of 1,000 iterations, with sampling from a further 10,000 iterations for each chain. To monitor convergence, trace plots, and the Gelman–Rubin convergence diagnostic (Rhat) were used for all parameters. As is conventional for such analyses, results are presented as hazard ratio (HR) or odds ratio (OR) with 95% credible intervals (CrI) and as the probability of minimum clinical benefit. All models were adjusted by key prognostic variables at baseline (age, presence of diabetes and SpO2).
Hospital length of stay, and duration of ventilation were assessed under the frequentist approach using sub-distribution HR derived from a Fine-Gray competing risk model with death before the event treated as competing risk and presented in cumulative incidence plots.
It was expected that the effect of ANGII would be influenced by the presence of renal dysfunction. Thus, in the present study we assessed the different effect of the drug in the subgroup of patients with abnormal serum creatinine at admission (defined as creatinine > 1.10 mg/dL in females and > 1.20 mg/dL in males). To explore the potential heterogeneity of treatment effect among these subgroups, a Bayesian binomial model was applied and the posterior distribution was sampled using Markov Chain Monte Carlo simulations. Results are displayed through the probability distribution of HR or OR for the subgroups, and as the probability of a higher benefit in a specific subgroup. Since no previous information about the impact of ANGII in COVID-19 is available, all analyses used non-informative flat priors, to have the posteriors completely dominated by the likelihood (reflecting the data).
Due to the nature of the study, and since the sample size was small and the number of events was low, all analyses should be considered exploratory and hypothesis generating only. All analyses were conducted in R v.3.6.3 (R Foundation) [13].