Correspondence (reply): In Reply

We welcome Dr Raeder’s comment, especially regarding the rapid and consequently often successful treatment of the trigger of acute kidney injury.

The term of in-hospital mortality used in the article (1) refers to those patients with acute kidney injury who did not survive their inpatient stay. A causal association between disorder/syndrome and death is not a prerequisite for using this term.

The point of electronic alerting systems for acute kidney injury is the immediate capture and passing on of information of acute reduction in renal function—no matter what the cause is—to the treating doctors. Current studies are investigating the question of which groups of patients with which underlying etiology of acute kidney injury benefit the most from the immediate initiation of consented treatment measures, from cross-sectoral information exchange in follow-up care, and from histological investigation results. A proof that the course of acute kidney injury can be positively influenced in the sense of improved renal function exists in the shape of subgroup analyses from studies in which the transmission of the information “acute kidney injury” was linked to concrete treatment recommendations.

We agree with the comments of Dr Kiehntopf and colleagues, in which they describe the influence of the measuring technique for creatinine on the frequency of the diagnosis of acute kidney injury and the correspondingly defined patient cohort. In view of the named treatment period and the hospital specific treatment codes, the proportion of patients who were treated as inpatients at a German university medical center and had acute kidney injury is an estimated 5–7%. Of the 130 cases reported as having acute kidney injury, 95 cases were detected by the enzyme based test as well as the kinetic test. Another 15 cases were detected by the enzyme based test alone, and 20 cases were detected kinetically according to Jaffé. If an institute of laboratory medicine uses only one of those two tests, the proportion of detected cases with acute kidney injury will differ by <5% between the methods. The clinical relevance of patient populations with acute kidney injury discovered by only one or the other measuring technique will be able to be assessed on the basis of other proofs. In case of doubt, the laboratory should be consulted to clarify the measuring technique and to initiate further measures if required. However, documenting the creatinine measuring technique seems recommendable even now of the planning, analysis, and interpretation of studies.