Renal angina: concept and development of pretest probability assessment in acute kidney injury

Abstract

The context of a diagnostic test is a critical component for the interpretation of its result. This context defines the pretest probability of the diagnosis and forms the basis for the interpretation and value of adding the diagnostic test. In the field of acute kidney injury, a multitude of early diagnostic biomarkers have been developed, but utilization in the appropriate context is less well understood and has not been codified until recently. In order to better operationalize the context and pretest probability assessment for acute kidney injury diagnosis, the renal angina concept was proposed in 2010 for use in both children and adults. Renal angina has been assessed in approximately 1,000 subjects. However, renal angina as a concept is still unfamiliar to most clinicians and the rationale for introducing the term is not obvious. We therefore review the concept and development of renal angina, and the currently available data validating it. We discuss the various arguments for and against this construct. Future research testing the performance of renal angina with acute kidney injury biomarkers is warranted.

Figure 1

Hazard tranches to incorporate an operating concept into reginal angina. Each hazard tranche (HT) has equivalent net risk for the development of acute kidney injury (AKI). RA, reginal angina.

Figure 2

Renal angina index for children. The renal angina index establishes point values for both risk tranche and injury threshold to use in computing a composite score. The integer values assigned for each risk tranche (that is, 1, 3, 5) are derived directly by comparing cohorts extracted from established pediatric acute kidney injury (AKI) data in an epidemiologic study. The integer values given for injury are denoted as two-exponent to signify doubling of injury for incremental increases in creatinine or fluid overload on admission. The computed index ranges from 1 to 40. Through sensitivity analyses, cutoff value ≥8 has been established as fulfillment of renal angina. eCrCl, estimated creatinine clearance; FO, fluid output; OR, odds ratio; PICU, pediatric ICU; ppCRRT, positive-pressure continuous renal replacement therapy. Adapted with permission from [13].