Background: It has been observed that the Medical Service (Medizinischer Dienst, an auditing body of the German statutory health insurance system) is more likely to audit the bill for a hospitalization in a psychosomatic clinic if the patient carries a secondary diagnosis of obesity.
Methods: In an exploratory study, we retrospectively analyzed 771 datasets collected in 2019 as part of the standard documentation of acute psychosomatic hospitalizations.
Results: In 2019, the Medical Service audited bills for psychosomatic hospital - izations much more often in obese than in non-obese patients (odds ratio [OR] 2.499; 95% confidence interval [1.69; 3.69]). This was accounted for by a very high audit rate for patients with a secondary diagnosis of grade 3 obesity (OR = 3.972 [2.30; 6.86]). The audit categories "quality of coding" and "possible incorrect admission" were examined.
Conclusion: Treatments of markedly obese inpatients that incurred greater expenses presumably led to a higher hospitalization audit rate as an automatic consequence of the auditing algorithms used. An unintentional statistical discrimination arose from the unjustified linkage of the audit category "quality of coding" of the secondary diagnosis (obesity) with the audit category "possible incorrect admission" with regard to the main diagnosis. Similar effects may be occurring with economically relevant secondary diagnoses in other areas of medicine as well.