[The relationship of in-hospital and post-discharge complications and implications for quality measurement in hip replacement surgery - an analysis of AOK administrative data]

Aim: This study analyses the information gain achieved by additionally taking into account complications in the follow-up period instead of merely considering in-house events for a hospital-based quality measurement using the example of hip replacement.

Method: The analysis was performed with anonymous statutory health insurance data (AOK) for the years 2007-2009 within the framework of the quality measurement method "Quality Assurance with Administrative Data (QSR)". It included cases of hip replacement surgery due to osteoarthritis. In order to analyse hospital-related outcome quality, 6 quality indicators were formed (revision surgery within 365 days, surgical complications within 90 days, thrombosis/pulmonary embolism within 90 days, femur fracture within 90 days, mortality within 90 days and complication index). For each hospital, the adjusted SMRs (standardised mortality or morbidity ratio) with 95% confidence intervals were calculated. The relation between the in-hospital and the follow-up SMR was analysed by Spearman's rank correlation coefficient. Furthermore, the percentage consistency of hospital SMRs categorised into quartiles on the basis of in-hospital and post-discharge events was determined.

Results: A total of 154 470 AOK patients from 930 hospitals were included in the analysis. The hospitals had a median overall complication rate of 11,22%. One quarter of the hospitals had complication rates of 8,18% or below. Another quarter of the hospitals had complication rates nearly twice as high (≥15,49%). Nearly one-third of all complications occurred after the initial hospitalisation. Regarding clinic-related complications, there was little correlation between the events in the initial case and during follow-up (r<0,3) for all indicators. The order of the hospitals defined by quartiles of SMR changed significantly by adding the complications in the follow-up for the indicators considered (min 21%, max 47% changes between quartiles). In particular, for the indicators revision and death, a change in the SMR quartile occurred in almost 50% of all hospitals.

Conclusion: Quality assessment of hip replacement surgery based exclusively on in-house events is quite unreliable. On the one hand, nearly a third of all complications occur in the follow-up period. On the other hand, predicting the occurrence of post-discharge events from in-house complications of a clinic is not considered acceptable for the indicators analysed in this study.