An agreement was obtained from Professor Ely (Vanderbilt University Medical Center, Nashville, USA), the designer of the CAM-ICU scale. The patients involved were informed about the voluntary and anonymous nature of the study. A written consent was obtained directly from each one. However, for the patients who were temporarily unable to decide for themselves, written consents were obtained from their relatives. Later, these patients were informed about the study and written consent was obtained.
Translation and cultural adaptation procedures
The translation and cultural adaptation procedures were performed in four steps according to the protocol of the “Messaging Application Programming Interface Research Institute" . First, the translation was carried out from English into the Tunisian dialect by two bilingual translators (IBS and SK in the authors’ list). A reconciliation of the two forward translations was performed. Secondly, a back-translation was conducted by a bilingual translator who had no information about the original version. Thirdly, a meeting involving all the development team was held to check the conformity of the back-translated text with the original one. All the differences between the original and the back-translated versions were discussed. Suggestions for the items that could be ambiguous or misunderstood were encouraged. Responses and comments were taken into consideration in the reconciled and agreed upon forward-translated version of the Tunisian CAM-ICU. Finally, the back-translated version was sent to Professor Ely for approval.
The material related to the Tunisian translated version of the CAM-ICU is currently available at the following website: www.icudelirium.org (last access: March 22, 2020).
Delirium assessment by CAM-ICU
The CAM-ICU scale comprises four features. Feature-1 an acute change or fluctuation in the course of the mental status. Feature-2 inattention and it is assessed using attention screening examination letters (auditory vigilance random letter task) and pictures (visual picture recognition). Feature-3 an altered level of consciousness evaluated using the Richmond Agitation-Sedation Scale (RASS). Feature-4 disorganized thinking using “yes/no” questions and commands. Delirium is considered positive when features 1 and 2 plus either feature 3 or 4 are present .
Pre-testing was performed on a small sample of critically ill monolingual (target language, Tunisian dialect) patients. This sample was excluded from the final statistical validation group. Both CAM-ICU trained raters (SK and NK in the authors’ list) reported no difficulty or ambiguity.
A prospective cohort study was conducted in a 9-bed medical ICU at FARHAT HACHED university hospital (Sousse, Tunisia) from October 2017 to June 2018. The average number of ICU admissions is 260 per year and the main reason for admission is acute exacerbation of chronic obstructive pulmonary disease.
To obtain representative and reliable data, the required sample size was estimated using the following equation : n= (Zα/2² p q)/∆². “Zα/2” (=1.96) was the normal deviate for a one-tailed hypothesis at a 5% level of significance; “p” (=0.19) was the frequency of delirium among Tunisian ICU patients in a previous study ; “q” (=0.81) was equal to “1-p”, “∆” (=7%) was the arbitrarily chosen precision. Using the aforementioned equation, the estimated sample size was 120 patients.
Populations and procedure
All the patients consecutively admitted to the ICU for more than 24 hours and having a RASS  greater than or equal to “-3” were assessed for delirium. The patients with stroke, dementia, psychosis or persistent coma were not included in this study.
The following patients’ demographic and clinical characteristics were collected: age (years), sex, addictive behaviours (smoking, alcohol abuse, drug addiction), underlying diseases, Charlson index , reasons for admission, and Simplified Acute Physiological Score (SAPS-II) .
Delirium detection was performed by two raters who received training on using the Tunisian version of the CAM-ICU. Rater 1 (SK in the authors’ list) is a well-trained resident in critical care having more than two years of experience. Rater 2 (NK in the authors’ list) is a well-trained medical intern in ICU at the time of the study. For a reference standard evaluation, a psychiatrist (BA in the authors’ list) applied the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-V) criteria  for the delirium diagnosis. Examinations were performed less than four hours apart. The raters were blinded to each other's findings. Each patient was assessed once.
The CAM-ICU inter-rater reliability was tested by comparing the Tunisian CAM-ICU rating by two raters using the Cohen’s kappa (κ) coefficient with 95% confidence interval (95% CI). “κ” coefficient was used to calculate the concordance between the two raters, defining “κ” > 0.61 as “substantial” and “κ” > 0.81 as “almost perfect” . The CAM-ICU concurrent validity was assessed by calculating the internal consistency (Cronbach’s α coefficient), sensitivity, specificity as well as positive and negative predictive values (PPV and NPV, respectively) for the two Tunisian CAM-ICU raters. The calculations were based on considering the DSM-V criteria  as the reference standard. Data were analyzed using Epi info. Statistical significance was considered at p < 0.05.