Acute Kidney Injury Predictor Validation Study

Inclusion and exclusion criteria:

All adult patients admitted to the UZ Leuven's ICU after the approval of the study by the local Ethical Committee and before June 30th 2018 will be included in the study. The only exclusion criteria will be the presence of end-stage renal disease before or of AKI on ICU admission.

Computer predictions:

Elements from laboratory reports, clinical history and physiological monitoring will be used both by clinicians and by the computer algorithm to estimate the risk of AKI. Such measurements are part of the routine standard care in the ICU: no additional exam will be required for this study. These values are regularly stored in the electronic health care system (KWS, Klinisch Werkstation and iMDsoft's MetaVision). They will be retrieved in read-only mode when needed for formulating the predictions. The retrieval will take place regularly on a weekly basis in order to limit the amount of time that patients' identification data will be stored for the study.

In detail, the following parameters will be used by the computer model:

• upon admission: age, baseline serum creatinine (lowest value of the previous 3 months; if not available, calculated using the Schwartz formula), surgical or medical category (transplant surgery / cardiovascular surgery / abdominal or pelvic surgery / thoracic surgery / other: medical, trauma, other surgery), planned admission (yes / no), history of diabetes (yes / no), blood glucose, suspected sepsis (yes / no), and hemodynamic support (none / mechanical / pharmacological / both);
• on the first morning after admission: serum creatinine (measured in the morning), APACHE II score, blood lactate (worst value since admission), total bilirubin, and hours of ICU stay;
• at 24h after admission: hourly urine output, doses of inotropes and vasopressors, and continuous arterial blood pressure values.

Physicians predictions:

Physicians' predictions will be collected alternatively through interviews conducted personally by one of the investigators or by means of a questionnaire compiled by the physicians themselves. To parallel the timing of AKIpredictor, clinicians' predictions will be gathered at three time-points:

• admission predictions: at the earliest after admission (up to 3h);
• morning predictions: on the first morning after admission, right before or after the handoffs that take place between 8.30 and 9.00 AM;
• 24h predictions: at 24h after admission (up to 24h+3h).

Interviews to multiple physicians about the same patient in the same time frame will be encouraged, as long as they are not influenced by one another (junior resident, senior resident, staff member).

In every prediction, both a continuous (on a 0-100 % scale) and a binary (yes / no) estimate of AKI risk will be inquired. A self-assessed degree of confidence about the prediction will also be tracked (very confident / medium confident / not confident at all). The exact time at which the human prediction is collected will be saved. Finally, data about the clinician expressing the prediction will be tracked: age, gender, seniority (see above), years of ICU experience.

Endpoint assessment The effective development of AKI will be diagnosed in agreement with the 2012 KDIGO guidelines [1]. To take into account AKI occurring outside the ICU where hourly measurements of urine output are not recorded, only the creatinine criterion will be used. Serum creatinine values will be collected from the electronic health record system KWS (Klinisch WerkStation) each day for 7 days following ICU admission. This biochemical exam is routinely performed on a daily basis in any hospitalized patient unless considered at low risk for complications, and it is always required if there's suspicion of an acute renal insult. For these reasons, potential missing creatinine values will be considered evidence of an improving patient and absence of AKI for that day.

ICU discharge and eventual readmission will also be tracked for secondary analyses. The death of the patient will also be recorded and included among the negative outcomes.

Assessment of efficacy The efficacy of both predictors will be evaluated with the construction of ROC curves. Due to the lack of previous studies on the subject, a current estimate of the accuracy of clinicians' prediction of AKI is not currently available. Appropriate sample size calculations to obtain sufficient power are therefore not feasible at the moment. Statistical analysis will be performed at the end of the data collection as follows. A ROC curve will be plotted both for the computer-based AKIpredictor and the continuous (%) estimate of AKI risk assessed by the clinicians at each of the three time-points (upon admission, on day 1 and at 24 hours). The area under the curve (AUC) of each plot will be calculated. The AUCs will then be compared in pairs by bootstrapping, and a significance value of the comparison will be derived. Subgroup analysis will be performed with the same approach.

Ethics and regulatory approvals:

The trial will be conducted in compliance with the principles of the Declaration of Helsinki (current version) and the principles of good clinical practice. This protocol will be submitted to the ethical committee of the UZ Leuven. Any eventual subsequent protocol amendment will also be submitted to the ethical committee and Regulatory Authorities for approval.

By virtue of its non-interventional nature and that all the data will be stored in anonymized fashion, informed consent will not be required from the subjects if this is deemed appropriate by the local Ethical Committee. The investigators shall treat all information and data relating to the study as confidential and shall not disclose such information to any third parties or use such information for any purpose other than the performance of the study. The collection, processing and disclosure of personal data, such as patient health and medical information is subject to compliance with applicable personal data protection and the processing of personal data (Directive 95/46/EC and Belgian law of December 8, 1992 on the Protection of the Privacy in relation to the Processing of Personal Data).