One challenge in analyzing hospital administrative data consists in specifying the units under study on the basis of the available information in such a way that systematic errors and consecutive misinterpretation of the results—for example, as a result of poorly defined groups of treatment cases—are avoided (1). However, we noticed inaccuracies in the case definition by Baum et al. (2), which make it difficult to interpret the results of their study.
On considering the German procedure classification (Operationen- und Prozedurenschlüssel, OPS) codes for including study units in eTable 1 (2) it transpires that the codes are in some cases not consistent with the entities named in the text (p 740). For example, for thyroid procedures (hemithyroidectomy, thyroidectomy), the codes for thyroidectomies are missing. For gastrointestinal surgery (4/5 gastrectomy, gastrectomy), codes for gastrectomies and 2/3 resections are listed, but the code for 4/5 resections is not. For hernia surgery (TAPP, TEP, Lichtenstein procedures), the wrong codes are listed for the Lichtenstein procedure (the codes given, 5–530.33 and 5–530.34, were not yet included in the OPS during the study period).
In the discussion, Baum et al. refer to the analyzed colorectal and gastric resections as “oncological procedures” (p 744, p 745). These study units were, however, only chosen because of procedure codes, without taking into account the relevant diagnostic codes. For example, in fewer than half of all colorectal resections undertaken in German hospitals, colon or rectal carcinoma are coded as the principal or secondary diagnosis (3). This probably also explains the differences in in-hospital mortality in the international comparison, which were discussed in this context.
In conclusion, the statement in the abstract, “The in-hospital mortality after visceral surgery in Germany is unknown” is incorrect. We refer the authors to numerous publications of our working group ( may serve as an example) and those of other colleagues.
Dr. PH Ulrike Nimptsch
Technische Universität Berlin
Fachgebiet Management im Gesundheitswesen, Berlin
Dr. med. Christian Krautz
Klinik für Allgemein- und Viszeralchirurgie, Erlangen
Conflict of interest statement
Dr Nimptsch received a honorarium from 3M Deutschland GmbH
Dr Krautz declares that no conflict of interest exists.
|1.||Nimptsch U, Spoden M, Mansky T: Variablendefinition in fallbezogenen Krankenhausabrechnungsdaten – Fallstricke und Lösungsmöglichkeiten. Gesundheitswesen 2019; DOI: 10.1055/a-0977–3332 [Epub ahead of print] CrossRef MEDLINE|
|2.||Baum P, Diers J, Lichthardt S, et al.: Mortality and complications following visceral surgery—a nationwide analysis based on the diagnostic categories used in German hospital invoicing data. Dtsch Arztebl Int 2019; 116: 739–46 VOLLTEXT|
|3.||Nimptsch U, Mansky T: G-IQI | German Inpatient Indicators Version 5.2. Bundesreferenzwerte für das Auswertungsjahr 2016. Working Papers in Health Services Research Vol. 1. Berlin: Universitätsverlag der Technischen Universität Berlin 2019. DOI: www.dx.doi.org/10.14279/depositonce-9067.|
|4.||Krautz C, Nimptsch U, Weber GF, Mansky T, Grützmann R: Effect of hospital volume on in-hospital morbidity and mortality following pancreatic surgery in Germany. Ann Surg 2018; 267: 411–17 CrossRef MEDLINE|