This investigation on informed consent was an observational substudy of a clinical trial about inflammation, described elsewhere . The present study was designed in two steps: first, a protocolled informed consent procedure was conducted then the informed consent was given by the patient, and second, a patient interview was held 10 ± 2 days later by the same investigator about their participation, the purpose, and the risks related to the clinical trial on inflammation.
This study was performed in a 20-bed surgical ICU of a tertiary-university-affiliated teaching hospital receiving 1,600 patients per year.
Type of participants
Patients admitted to the ICU after a major surgery or trauma were eligible. To give their consent to participate in the clinical trial on inflammation, patients had to present with a GCS score of 15, be fully oriented and free of mechanical ventilation, and judged competent by both the investigator and the attending physician. Patients who refused to participate, met any of the exclusion criteria for the clinical trial on inflammation, and those whose next-of-kin gave consent were not considered for the present study. Furthermore, incompetent or non-French-speaking patients, and those with psychiatric disorders, senile dementia or other intellectual disabilities were not included.
The informed consent procedure
A protocoled procedure detailing how to obtain informed consent was developed to ensure that the two investigators contributing to the study obtained consent in an identical manner. The investigators were physicians who were not caring for the patients enrolled in the study. Informed consent was obtained on the ICU admittance date, after a 20-minute individual oral presentation. During this presentation, the investigator explained the clinical trial on inflammation, emphasizing two clinical trial components: the purpose and its related risks. The defined keyword for the clinical trial purpose was inflammation. The clinical trial risk for the patient was that 10 ml of their blood would be drawn daily for the first five days of their ICU stay, and a final blood draw would be required at day 28. The investigator told the patient that the risk was minimal.
The patient then received a one-page informative leaflet. At the end of this procedure, the investigator asked the patient if he had any questions about the clinical trial before signing the informed consent form. The investigator noted whether the patient asked any questions and/or if he read the informative leaflet in his presence. These two attitudes of the patient (asking one or more questions and reading the informative leaflet) were defined a priori in the consent procedure. No other attitudes of the patient were recorded or tested.
This informed consent procedure conforms to recommendations on the ethical conduct of clinical research involving patients in the ICU .
Patient age, gender, history of daily alcohol intake type of admission and diagnosis, as well as Simplified Acute Physiological Score second version (SAPS II)  were recorded on admission to the ICU. The lengths of mechanical ventilation and ICU stay were also noted.
When informed consent was obtained, clinical and laboratory values, the Sequential Organ Failure Assessment (SOFA) score , and medical treatment given within the 24 hours before and after the consent procedure were assessed.
At 10 ± 2 days (range), the investigator met the patient to plan the blood sampling to be performed on day 28. At this time, the investigator assessed whether the patient could recall participation in the clinical trial and/or any of the clinical trial components.
The primary endpoints were the ability of the patient to recall participation in the clinical trial, as well as the purpose and related risks of the clinical trial. As secondary endpoints, we investigated whether asking questions about the clinical trial or reading the informative leaflet was related to the recall.
Patients who could report their participation in the clinical trial on inflammation, the clinical trial purpose and the related risks were assigned to the 'complete recall' group. Patients lacking one or more components were assigned to the 'incomplete recall' group.
The clinical trial on inflammation itself, as well as the informative leaflet and the consent form, were approved by the Ethical Committee for Human Research of our institution. Specific informed consent had not been sought for this study. The educational status of the patient, that was the sole data not available in the dataset of the clinical trial, was subsequently retrieved from the administrative file.
StatView for Windows version 5.0.1 (SAS Institute Inc., Cary, NC, USA) was used for statistical analysis. Patients were stratified as having either complete or incomplete recall; these data were compared separately by using a two-tailed Fisher's exact test, an unpaired t test or a Mann–Whitney U test, as deemed appropriate. We also assessed the sensitivity, specificity, the positive predictive value, the negative predictive value and the likelihood ratio of factors that were statistically significant on the basis of the univariate analysis performed to predict complete recall of the clinical trial. Odds ratios with 95% confidence intervals were calculated to estimate the effect size of risk factors associated with complete recall. All tests were two-tailed; p < 0.05 was considered significant.