An observational study in Acute Kidney Injury, sponsored by Izmir Katip Celebi University. Not yet recruiting at 1 site in Turkey (Türkiye). Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-07.
Sponsored by Izmir Katip Celebi University · Observational
Acute kidney injury (AKI) is a frequent complication of critical illness and is associated with increased morbidity and mortality. Early identification of patients at risk of progressing to moderate-to-severe AKI may facilitate closer monitoring and timely implementation of kidney-protective strategies.
This prospective observational cohort study will evaluate the predictive performance of the Renal Angina Index (RAI) for the development of Kidney Disease: Improving Global Outcomes (KDIGO) stage 2 or stage 3 AKI in adult intensive care unit patients. Consecutive eligible patients admitted to the participating adult intensive care unit will be enrolled. The RAI will be calculated 24 hours after ICU admission using routinely available clinical characteristics and the change in serum creatinine between ICU admission and 24 hours.
The primary outcome will be the development of KDIGO stage 2 or stage 3 AKI during the subsequent 48 hours. AKI staging will incorporate serum creatinine, urine-output, and renal replacement therapy criteria according to KDIGO definitions. The predictive performance of RAI will be evaluated using receiver operating characteristic analysis and the prespecified RAI threshold of ≥10.
Secondary outcomes will include 7-day and 30-day intensive care unit mortality, intensive care unit length of stay, and duration of invasive mechanical ventilation.
This single-center, prospective, noninterventional cohort study will evaluate the predictive performance of the Renal Angina Index (RAI) for subsequent development of moderate-to-severe acute kidney injury in critically ill adults. Consecutive eligible patients admitted to the participating adult intensive care unit will be screened for enrollment irrespective of admission source or subsequently calculated RAI category. Clinical management will remain entirely under the responsibility of the treating team, and no treatment or diagnostic intervention will be assigned by the study protocol.
The RAI will be calculated 24 hours after ICU admission. The clinical-risk component will be determined using the highest applicable prespecified risk category at ICU admission, and the renal-injury component will be determined from the absolute change in serum creatinine between ICU admission and 24 hours. The resulting RAI ranges from 1 to 40, with RAI ≥10 representing the prespecified high-risk threshold. RAI \<10 and RAI ≥10 will be evaluated as prespecified risk strata within a single observational cohort.
The primary outcome will be development of KDIGO stage 2 or stage 3 AKI during the 48 hours following RAI calculation. AKI severity will be classified using serum creatinine, urine-output, and acute renal replacement therapy criteria. Stage 2 AKI will be defined as serum creatinine 2.0-2.9 times baseline or urine output \<0.5 mL/kg/hour for at least 12 hours. Stage 3 AKI will be defined as serum creatinine ≥3.0 times baseline, an increase in serum creatinine to ≥4.0 mg/dL in the setting of AKI, initiation of acute renal replacement therapy, urine output \<0.3 mL/kg/hour for at least 24 hours, or anuria for at least 12 hours. The highest KDIGO stage reached by any applicable criterion will determine AKI severity. KDIGO Baseline serum creatinine for AKI staging will be defined as the most recent stable outpatient serum creatinine measurement obtained within the 6 months preceding ICU admission. Participants without an eligible baseline serum creatinine measurement will be excluded, and no alternative baseline creatinine estimation or imputation will be performed. The baseline serum creatinine used for KDIGO staging will be distinct from the ICU-admission serum creatinine used to calculate the RAI renal-injury component.
Serum creatinine measurements obtained during routine care at ICU admission and approximately 24, 48, and 72 hours after admission will be recorded. Urine output will be prospectively obtained from routine clinical documentation and evaluated according to KDIGO duration and weight-adjusted thresholds. Renal replacement therapy initiation and its indication will also be recorded. Participants who have already developed KDIGO stage 2 or stage 3 AKI at or before the 24-hour RAI assessment will not be included in the primary incident-AKI prediction analysis, because the target outcome will already have occurred before application of the index test.
Discrimination of the RAI for development of KDIGO stage 2-3 AKI will be evaluated using the area under the receiver operating characteristic curve with 95% confidence intervals. For the prespecified threshold of RAI ≥10, sensitivity, specificity, positive predictive value, negative predictive value, positive and negative likelihood ratios, and overall classification accuracy will be reported with 95% confidence intervals. An alternative threshold based on the Youden index will be considered exploratory.
Secondary clinical outcomes will include 7-day and 30-day intensive care unit mortality, intensive care unit length of stay, and duration of invasive mechanical ventilation.
1,595 studies on the registry are indexed under Acute Kidney Injury; 371 are open to participants now.
This study's planned enrollment of 324 is above the median of 150 across 773 observational studies indexed under Acute Kidney Injury.
Browse Acute Kidney Injury studies →Izmir Katip Celebi University is the lead sponsor of 191 studies on the registry; 40 are open to participants now.
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Adult patients admitted to the participating adult intensive care unit will be considered for enrollment. Consecutive admissions meeting the eligibility criteria will be screened regardless of admission source or subsequently calculated Renal Angina Index category. The Renal Angina Index will be calculated 24 hours after ICU admission using routinely collected clinical and laboratory data.
Exclusion Criteria:
A single prospective cohort of consecutive eligible adult patients admitted to the participating intensive care unit. The Renal Angina Index (RAI) will be calculated 24 hours after ICU admission using routinely collected clinical and laboratory data. Participants will subsequently be analyzed according to the prespecified RAI strata of \<10 and ≥10. No treatment assignment will be made by the study protocol.
Diagnostic Test: Renal Angina Index Assessment
The Renal Angina Index will be calculated 24 hours after ICU admission using routinely available clinical and laboratory information. The RAI will be used as a prognostic index to evaluate the risk of subsequent KDIGO stage 2 or stage 3 acute kidney injury. No treatment, diagnostic procedure, or therapeutic intervention will be assigned on the basis of the RAI by the study protocol.
Area Under the Receiver Operating Characteristic Curve of the Renal Angina Index for Predicting KDIGO Stage 2 or Stage 3 Acute Kidney Injury
The predictive discrimination of the Renal Angina Index (RAI), calculated 24 hours after intensive care unit admission, for the development of Kidney Disease: Improving Global Outcomes (KDIGO) stage 2 or stage 3 acute kidney injury (AKI) during the subsequent 48 hours will be assessed using the area under the receiver operating characteristic curve (AUROC), with a 95% confidence interval. The target outcome will be development of KDIGO stage 2 or stage 3 AKI within 48 hours after RAI calculation. KDIGO stage 2 AKI will be defined as serum creatinine 2.0-2.9 times baseline or urine output \<0.5 mL/kg/hour for at least 12 hours. KDIGO stage 3 AKI will be defined as serum creatinine ≥3.0 times baseline, serum creatinine ≥4.0 mg/dL in the setting of AKI, initiation of acute renal replacement therapy, urine output \<0.3 mL/kg/hour for at least 24 hours, or anuria for at least 12 hours. When more than one criterion is met, the highest KDIGO stage reached will determine AKI severity.
Time frame: Within 48 hours after RAI calculation
Development of KDIGO Stage 2 or Stage 3 Acute Kidney Injury Within 48 Hours After RAI Calculation
The number and proportion of participants who develop Kidney Disease: Improving Global Outcomes (KDIGO) stage 2 or stage 3 acute kidney injury (AKI) during the 48-hour period following calculation of the Renal Angina Index (RAI) will be recorded. KDIGO stage 2 AKI will be defined by either of the following: Serum creatinine 2.0-2.9 times the baseline value; or Urine output \<0.5 mL/kg/hour for at least 12 hours. KDIGO stage 3 AKI will be defined by any of the following: Serum creatinine ≥3.0 times the baseline value; Serum creatinine ≥4.0 mg/dL in the setting of acute kidney injury; Initiation of acute renal replacement therapy; Urine output \<0.3 mL/kg/hour for at least 24 hours; or Anuria for at least 12 hours. If serum creatinine and urine-output criteria correspond to different KDIGO stages, the highest stage reached will determine AKI severity. Baseline serum creatinine will be defined as the most recent stable outpatient serum creatinine measurement obtained within the
Time frame: Within 48 hours after RAI calculation
7-Day Intensive Care Unit Mortality
The number and proportion of participants who die in the intensive care unit within 7 days after ICU admission will be recorded. Deaths occurring after live discharge or transfer from the ICU will not be classified as ICU deaths.
Time frame: Within 7 days after ICU admission
30-Day Intensive Care Unit Mortality
The number and proportion of participants who die in the intensive care unit within 30 days after ICU admission will be recorded. Deaths occurring after live discharge or transfer from the ICU will not be classified as ICU deaths.
Time frame: Within 30 days after ICU admission
Intensive Care Unit-Free Days Through Day 30
The number of days alive and free from the intensive care unit (ICU) during the first 30 days after ICU admission will be calculated. Participants who die before day 30 will be assigned 0 ICU-free days. Participants who remain in the ICU through day 30 will also be assigned 0 ICU-free days. For participants discharged alive from the ICU before day 30, ICU-free days will be calculated as the number of days alive and outside the ICU through day 30. Any subsequent ICU readmission during this period will not be counted as ICU-free time. Higher values indicate a more favorable outcome.
Time frame: From ICU admission through day 30
Ventilator-Free Days Through Day 30
Ventilator-free days will be defined as the number of days during the first 28 days after ICU admission that the participant is alive and free from invasive mechanical ventilation delivered through an endotracheal tube or tracheostomy. Participants who die before day 28 will be assigned 0 ventilator-free days. Participants who remain invasively mechanically ventilated through day 28 will also be assigned 0 ventilator-free days. For participants successfully liberated from invasive mechanical ventilation before day 28, ventilator-free days will be counted from successful liberation through day 28. If invasive mechanical ventilation is restarted, the intervening period will not be considered definitive ventilator-free time until final successful liberation. Participants who never receive invasive mechanical ventilation will have 28 ventilator-free days. Noninvasive ventilation and high-flow nasal oxygen will not be considered invasive mechanical ventilation for this outcome.
Time frame: From ICU admission through day 30
Plan to share: Undecided — De-identified individual participant data underlying the results reported from this study may be shared with qualified researchers upon reasonable request. Shared data may include demographic, clinical, laboratory, Renal Angina Index, acute kidney injury outcome, and prespecified secondary outcome variables necessary to reproduce the published analyses. Data sharing will be subject to approval by the principal investigator and the relevant institutional and ethical requirements. No directly identifiable participant information will be shared.
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Izmir Katip Celebi University