Utilization AKI risk stratification, termed renal angina index (RAI)

Utilization of Renal
Angina Index for prediction of subsequent severe acute kidney injury


Raina Kaur, Gurdeep Singh Dhooria, Puneet A.
Pooni, Deepak Bhat, Sidharth Bhargava, Shruti Kakkar, 

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Department of
Pediatrics, Dayanand Medical College and Hospital, Ludhiana, Punjab, India


Dr Gurdeep Singh

Department of
Pediatrics, Dayanand Medical College and Hospital, Ludhiana, Punjab, India

[email protected]



Acute kidney injury (AKI) is independently associated with worsened
morbidity and increased mortality in PICU. AKI risk stratification, termed
renal angina index (RAI) has been used in the west  to predict persistent severe AKI. Very few
studies have been done on application of renal angina index in PICU of a
developing country. Aim: To predict
severe subsequent AKI in children admitted in PICU using Renal Angina Index. Design: Prospective observational
study.  Methods: Children admitted
over one year in PICU between one month to 18 years of age with no previous
kidney disease were included. RAI assessment was done from 8-12 hours of
admission to PICU. RAI was calculated from product of Renal Risk  and Renal Injury score. Renal angina
positivity was defined as RAI  ? 8. On
day 4, serum creatinine is noted and GFR is calculated. RAI was correlated with
presence/absence of subsequent severe AKI. RAI positivity was also correlated
with duration of PICU stay, need for dialysis, mechanical ventilation and mortality.
Results: RAI positivity was seen in
16.7 % cases. Of the RAI positive cases, 36.2 % cases developed AKI at 4 days
compared to 2.3% in the RAI negative cases (p value 8) predicted Day-3 AKI with an
AUC of 0.883 95% confidence interval (CI) = 0.823-0.943. RAI > 8
positivity had a
high negative predictive value (NPV)
of 97.67% % (95% CI = 95.84-98.7
%), with sensitivity and specificity of  75% and 88.42 % , respectively, and positive
predictive value (PPV) of 35.29% (95% CI = 27.92-43.44 %).

prediction by GFR criteria and Fluid overload (FO %) criteria

predictive value of  RAI was broken down by composite factors
of kidney injury. The predictive value for Day-3 AKI by GFR score alone by AUC values was consistently
superior when compared to
fluid overload score (FO %) AUC 0.877 (95% CI = 0.817-0.936) vs
0.774 (95% CI = 0.685- 0.864).
The AUC for
RAI for Day-3 AKI improved when
RAI incorporated worse of the two scores (GFR score/FO score). (AUC
0.883(95% CI= 0.823-0.943). 

versus KDIGO stage and PRISM score

Prediction of RA for Day-3 AKI was superior to KDIGO
stage 1 injury at admission;
fulfillment of renal angina demonstrated higher sensitivity (27.27%), PPV of 25%, NPV of 93.63%
and a higher
Youden’s index ( ____________) than KDIGO stage 1,
although specificity was found to be higher with KDIGO stage 1 (92.89%). Similar results were seen when RA was compared to KDIGO stages 2–3 (Youden’s index=_____). When compared directly, RAI outperformed PRISM-II for the
prediction of day 3 AKI. (AUC=0.764)
(95% confidence interval (CI) = 0.672-0.856).

Discussion:  Renal angina index was developed
by Goldstein to identify critically ill patients at greatest risk of AKI.10  In the current study, we looked at the
applicability of renal angina index in a tertiary care hospital of a developing
country and show that RAI can be used as bedside tool to prediction severe AKI following
PICU admission and also outperforms stage 1 KDIGO renal injury and PRISM II
score in this context. For
a clinician, the ability to predict the presence of severe AKI 3 days in
advance carries obvious benefit.

RAI was derived as a composite
of risk factors and clinical signs of AKI. The logic behind the equation
dictates that as a patient achieves higher risk they require less “clinical
sign of AKI” early on to fulfill renal angina. Similarly, if a patient has less
risk but shows more overt signs of clinical AKI signs, renal angina would also
be fulfilled.15 RAI
derivation was based on available AKI epidemiology reported in select pediatric
populations: children admitted to the ICU carry increased risk over the general
population (4.5–10%),16,17
children receiving bone marrow transplantation have ~3× risk (11–21%)18, and those who are intubated
and on vasopressor support carry nearly 5× risk versus the general ICU
population (51%). 3
The ‘signs of injury’ (i.e., kidney pain) in the RAI include GFR and fluid

Fluids are the second most
common intervention in acutely ill patients (after oxygen). The benefits of
early fluid resuscitation in patients with shock and acute kidney injury (AKI)
are already accepted. There is evidence that fluid administration beyond the
correction of hypovolaemia is associated with increased morbidity, a longer
hospital stay and mortality. In a recent article in Critical Care, Wang et al.
analysed the data of 2526 patients admitted to 30 intensive care units (ICUs)
in China and showed that even relatively small degrees of fluid overload were
independently associated with an increased risk of AKI and mortality 19.

In the Rajit
Basu et al study,
based on the most optimal Youden’s index (0.49) and highest negative predictive
value (to safely rule out development of subsequent AKI), an RAI > 8 was
taken as cutoff to label Renal Angina positivity.15 Only day 3 AKI was chosen to define outcome as most PICU
patients develop AKI within this time frame and it surpasses the time frame of
functional AKI (prerenal AKI). Also, time frame of 8 h was kept to assess fluid
overload as it was beyond the generally accepted window of ‘early goal-directed
therapy’ (EGDT) of resuscitation. 20

    In our study a
total of 413 patients were included. Day 0 Renal Angina positive was seen in
16.7% patients. Of  renal angina positive
patients 36.2 %  developed subsequent
severe AKI compared to 2.3 % of the other group, which was highly significant