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The renal angina index (RAI) a validated tool for risk stratification of acute kidney injury (AKI) in critically ill children. RAI has come to highlight the characteristics of renal injury, analogy to angina pectoris in suspicion of acute coronary syndrome in cardiology. Critically ill patients are predisposed to episodes of AKI that remains subclinical if based on serum creatinine and GFR alone.
The proposed mRAI (modified renal angina index) (Figure 2) predicts moderate to severe AKI within the first 7 days of ICU stay which outperforms serum creatinine and urine output. The study aims to evaluate the accuracy of the mRAI of predicting AKI among critically ill adult Filipino population and its association with MAKE (Major Adverse Kidney Events). The use of mRAI in AKI may be warranted to improve predicted performance of AKI biomarkers.
A retrospective cohort study including adult critically ill patients from January 1, 2019 to December 31, 2022. Using a cutoff value of 10, patients was dichotomized into “low risk” (<10) or “high risk” (>10). (Figure 1)
Using Open epi version 3, the sample size was computed using the 95% confidence level, 80% power, 4.7% AKI in MRAI<10 and 22.3% AKI in MRAI≥ 10 from the study of Ortiz-Soriano (2022). The minimum needed sample size was 69 per group or 138 patients. Random sampling will be employed using Microsoft Excel RAND Function of random numbers to select patient medical records from the masterlist of eligible patients of the institution.
Sample Size:X-Sectional, Cohort, & Randomized Clinical Trials
Two-sided significance level(1-alpha):
95
Power(1-beta, % chance of detecting):
80
Ratio of sample size, Unexposed/Exposed:
1
Percent of Unexposed with Outcome:
4.7
Percent of Exposed with Outcome:
22
Odds Ratio:
5.8
Risk/Prevalence Ratio:
Risk/Prevalence difference:
18
Kelsey
Fleiss
Fleiss with CC
Sample Size - Exposed
60
58
69
Sample Size-Nonexposed
Total sample size:
120
116
138
References
Kelsey et al., Methods in Observational Epidemiology 2nd Edition, Table 12-15
Fleiss, Statistical Methods for Rates and Proportions, formulas 3.18 &3.19
CC = continuity correction
Results are rounded up to the nearest integer.
The sensitivity, specificity, predictive values and area under the curve is used to determine diagnostic accuracy of the mRAI. Simple and multiple logistic regression analysis is used to control the effect of confounders in determining the association of mRAI to AKI. SPSS version 20 is used in the analysis.
The study also determined the association of the mRAI score with in hospital MAKE such as death within 7 days of ICU admission, new onset renal replacement therapy (Hemodialysis or Peritoneal Dialysis) and persistence of kidney dysfunction using the Chi square test. A p-value less than 0.05 is statistically significant.
There were 141 critically ill adult Filipino patient in a tertiary institution included in the study (Table 1). The mean age was 71 (12.6) years and ranges from 31 to 97 years. Most were males (61%) with comorbidities of hypertension (75.1%) and diabetes (51.4%). The most common diagnosis is Acute Coronary Syndrome 59 (41.8%) and Sepsis 24 (17%).
Table 1. Characteristics of the Study Population included in the study
Characteristics
Overall
Modified Renal Angina Index
p-value
<10 low risk
≥10 high risk
N=141
N =71
N=70
Demographic Profile
Age, mean (SD)
71.7 (12.6)
73.9 (11.0)
69.4 (13.7)
0.032*
Gender, Male
86 (61.0%)
47 (66.2%)
39 (55.7%)
0.202
Weight, mean (SD)
57.2 (9.8)
58.4 (11.0)
56.0 (8.3)
0.144
Comorbidities
Diabetes
Hypertension
COPD
Anemia
Others:
72(51.4%)
105(75.0%)
41 (29.1%)
69 (48.9%)
66 (46.8%)
32 (45.7%)
51(72.9%)
29 (42.8%)
20 (28.2%)
30 (42.3%)
40 (57.1%)
54 (77.1%)
12 (17.1%)
49 (70.0%)
36 (51.4%)
0.212
0.558
0.002*
0.001*
0.275
Use of nephrotoxic/contrast agents
SP CA
SP CABG
Use of IABP
49 (34.8%)
24 (17.1%)
18 (12.8%)
27 (38.0%)
14 (19.7%)
10 (14.1%)
22 (31.4%)
10 (14.5%)
8 (11.4%)
0.411
0.412
0.637
Surgical procedure
Abdominal Surgery
Endovascular surgery
Other surgery
4 (2.8%)
17 (12.1%)
42 (29.8%)
0 (0%)
6 (8.5%)
21 (29.6%)
4 (5.7%)
11 (15.7%)
21 (30.0%)
0.041*
0.185
0.956
Diagnosis
ACS/CAD
Sepsis
Pneumonia
CVD
Aneurysm
COVID-19
Other diagnosis
59 (41.8%)
24 (17.0%)
39 (27.7%)
6 (4.3%)
7 (5.0%)
2 (1.4%)
35 (49.3%)
18 (25.4%)
3 (4.2%)
1 (1.4%)
2 (2.8%)
24 (34.3%)
14 (20.0%)
5 (7.1%)
0.071
0.350
0.537
0.317
0.092
0.237
0.157
Acuity of Critical Illness
The proposed score can be used among critically ill adult Filipino patients which is an easy bedside tool for identification of moderate to severe AKI within 7 days of ICU stay. mRAI is a sensitive test with high negative predictive value, affirming its capability as a screening test for AKI. The study also concludes that a mRAI score of >10 is associated with In-Hospital Major Adverse Kidney Events.