Inpatient TIA and stroke care in adult patients in Germany - retrospective analysis of nationwide administrative data sets of 2011 to 2017
Comprehensive administrative data on TIA and stroke cases and treatment modalities are fundamental for improving structural conditions and adjusting future strategies of stroke care.
The nationwide administrative database (German federal statistical office) was used to extract all adult inpatient TIA and stroke cases and corresponding procedural codes for the period 2011–2017. Numbers were specified according to age, sex, stroke unit (SU) and critical care treatment (ICU), early transfer, and in-hospital mortality.
Inpatient adult TIA/stroke cases increased from annually 102,406 / 250,199 (2011) to 106,245 / 264,208 (2017). 84% of strokes were ischemic (AIS) also having the highest relative increase most likely due to more accurate coding within the time period, 68.2% of AIS were treated on SUs. 78% of hemorrhagic strokes were intracerebral hematomas (ICH; rather than subarachnoid hemorrhages [SAH]). Hemorrhagic strokes were increasingly treated on SUs (32.6% , 37.8% ). 68.8% of SAH were treated on ICUs (ICH:36.3%, AIS:10.3%). Early transfer in AIS increased (2.0 to 3.1%). Hemorrhagic strokes were associated with higher in-hospital mortality (SAH:19.6%, ICH:28.2%, AIS:7.3%).
The absolute increase of strokes presumably reflects the aging society and more awareness for cerebrovascular disease. The relative increase of AIS may be attributable to an increased neurological expertise. The increasing amount of early transfers in AIS reflects new specialized treatment options. Our findings reflect the need for structural adjustments in inpatient stroke care.
KeywordsIschemic stroke TIA Hemorrhagic stroke Administrative data Health care structure Health service research
The numbers of treated adult TIA and strokes cases in German hospitals has further increased in the observed time period 2011–2017. The proportion of hemorrhagic to ischemic stroke has not changed.
The rate of treatment on specialized wards like strokes units (SU) and intensive care units (ICU) has further increased for both ischemic and hemorrhagic stroke.
Hemorrhagic strokes are more frequently treated on ICUs, whereas cerebral infarctions and TIAs are more often treated on SUs. Hemorrhagic strokes are associated with higher in-hospital mortality.
For AIS, early transfer, e.g., to specialized neuro-vascular centers providing mechanical thrombectomy has increased in the time period.
The analysis of timely evolution of administrative data is important for future adjustments of infrastructure for inpatient stroke care.
The Global Burden of Disease Study recently provided data on global, regional and country-specific epidemiological data of stroke [1, 2, 3, 4]. Like in many other epidemiological analyses, insight in stroke epidemiology mostly relies on population-based, regionally limited, observational cohort or hospital-based registries, all of which bare specific constraints [5, 6, 7]. Due to the necessity to code both diagnoses and treatment procedures for reimbursement, the German DRG registry provides accurate and comprehensive data not only on all inpatient ischemic stroke / TIA cases and treatment modalities in German hospitals . Analysis of all hospitalized stroke cases can provide new insights into evolving trends of both ischemic and hemorrhagic stroke subtypes in everyday practice. Therefore, data from the German federal statistical office of all adult stroke patients hospitalized from 2011 to 2017 were used to identify frequencies of all inpatient stroke subtypes as well as treatment modalities on specialized wards. In addition, age- and sex-related differences, early transfer rates and in-hospital mortality rates were evaluated.
Analyses were based upon the latest German Diagnosis-Related Groups (G-DRG) data provided by the German federal statistical office (DRG-statistic, www.destatis.de) for the years 2011 to 2017. All in-patient stroke cases are encoded according to ICD-10-GM1 and relevant operating and procedure keys (OPS-301 codes) issued by the German Institute of Medical Documentation and Information (DIMDI). Here, the following ICD main diagnosis codes were considered: G45.0-G45.99 (transient ischemic attack, TIA); I60.0-I60.9 (subarachnoid hemorrhage, SAH); I61.0-I61.9 (intracerebral hemorrhage, ICH); I63.0-I63.9 (cerebral infarction, AIS); I64 (stroke, not specified as hemorrhage or infarction). All case numbers were aggregated at the level of the 3-digit ICD codes. The age-standardized rates were calculated using the standard population of Germany based on the census of 2011 (Federal Statistical Office: Statistics on Natural Population Movement) . In addition, the following OPS codes in combination with each considered main diagnosis were analyzed for all stroke subtypes2: 8–980 (basic intensive-care treatment); 8-98f (complex intensive-care treatment; from 2013 onwards); 8–981.0 (stroke unit treatment for more than 24 h and less than 72 h); 8–981.1 (stroke unit treatment for more than 72 h); 8-98b.*0/*1 (other acute stroke treatment without / with tele-consultation). For some analyses, OPS 8–980 and 8-98f were combined, as were the 3 subtypes of Stroke Unit care. Both first-ever and recurrent stroke cases were included, because the coding system cannot differentiate between them. Likewise, recurrent cerebrovascular events during hospital stay could not be analysed because these events are not coded consistently as a separate secondary diagnosis. Patients being transferred between hospitals during one treatment episode, (discharge key 06; transfer to another hospital), were censored accordingly in order to avoid any possible double/multiple coding. In addition, we assessed the number of acute stroke patients being transferred from one hospital to the other in the hyperacute phase for specific therapies such as mechanical thrombectomy, neurosurgical operations or intensive care treatment (so-called “hourly cases”). In-hospital mortality was assessed using discharge key 07 (death during hospital stay). For TIA and stroke subtypes, mean age with standard deviation, sex, and in-hospital mortality rate are provided. Only adult patients were considered.3 The maps of the regional frequency of ICH and AIS in Germany are based on the 413 administrative districts and independent cities in 2017. The age standardized rates are calculated for each district / city.
The number of TIA and stroke cases (SAH, ICH, AIS, and non-specified stroke) treated in German hospitals has increased from 2011 to 2017.
The proportion of AIS vs. hemorrhagic strokes (SAH, ICH) has remained constant in the observed time period.
Hemorrhagic strokes are more frequently treated on intensive care units (ICU), whereas cerebral infarctions and TIAs are more often treated on strokes units (SU).
Hemorrhagic strokes are associated with higher in-hospital mortality.
For AIS, early transfer to specialized neuro-vascular centers providing mechanical thrombectomy has increased.
For descriptive analyses, results are reported as absolute numbers and percentages. Age bracketing of results (20–44, 45–59, 60–69, 70–79, 80–89, ≥90 years of age) was determined before analysis. Statistical comparison of groups was performed with Chi-square-test and Yates´ correction. Taking into account multiple testing and the very high number of cases, only p-values of < 0.001 were considered statistically significant. To evaluate potential differences between hemorrhagic and ischemic stroke, we estimated the odds ratios (ORs) with the corresponding 95% confidence intervals (CIs) for each outcome of interest. Cumulative estimates were pooled under the random effects model. Both within and between group differences in all analyses were assessed with the Cochran’s test for heterogeneity. All analyses were performed with IBM SPSS Version 25 and the Stata Statistical Software Release 13 for Windows (College Station, TX, StataCorp LP).
Administrative data of patients treated and coded as different DRG-driven stroke subtypes in German hospitals in 2011, 2014, and 2017. Proportions of specific treatment types driven by respective OPS codes without patients not treated in specific units
age, m ± SD
72.1 ± 4.9
59.1 ± 3.0
72.1 ± 5.1
74.1 ± 5.2
78.6 ± 6.0
f. / 100.000
age, m ± SD
72.0 ± 4.9
60.1 ± 3.1
72.8 ± 5.2
74.0 ± 5.1
78.9 ± 6.1
f. / 100.000
age, m ± SD
72.0 ± 4.9
61.1 ± 3.2
73.1 ± 5.3
74.0 ± 5.1
78.2 ± 5.8
Treatment characteristics comparing patients treated in German hospitals for intracerebral hemorrhage (I61) and acute ischemic stroke (I63) between 2011 and 2017 (n = 1.721.447)
ICH (%, 95%PI)
AIS (%, 95%PI)
Δ 2017 vs. 2011
Total ICU treatment
basic ICU treatment
complex ICU treatment
Total SU treatment
SU treatment < 72 h
SU treatment > 72 h
Age adjusted inpatient rates / 100.000 inhabitants of patients treated and coded as different DRG-driven stroke subtypes in German hospitals in 2011, 2014, and 2017, according to sex
The proportion of AIS treated on “other stroke units” increased up to 2014 and stayed constant since then, accounting for 8.2% of all cases with AIS in 2017 (in 2011: without/with tele-consultation: 4.6/0.9%; in 2017: without/with tele-consultation: 5.2/3.0%). Early acute transfer to another hospital for further treatment increased only for AIS from 2.0  to 3.1% , while for hemorrhagic stroke there was a decrease of transfer rates (24.8 to 19.9% for SAH, 13.5 to 12.6% in ICH). In-hospital mortality was highest for hemorrhagic stroke (SAH 19.6% / ICH 29.3% ) compared to AIS (7.2%) and TIA (0.3%). The risk for in-hospital mortality was 6.4 fold (95%CI 5.98–9.92) higher for hemorrhagic stroke (see Additional file 3: Figure S3), especially in younger patients. In ICH, in-hospital mortality increased from 28.8% (2011) to 29.3% (2017), in AIS, in-hospital mortality decreased from 7.7% (2011) to 7.2% (2017).
Most of the review data refer to population-based, regionally limited, observational cohorts or hospital-based registries. Limitations of these study types have been discussed as focusing on urban areas, covering relatively small populations thus not reflecting the “true” composition of the population. Furthermore, the above mentioned studies have not analyzed the dispersion of treatment modalities such as specialized stroke unit (SU) or intensive care (ICU), which is a beneficial factor for patients´ outcome. Given high hospitalization rates in Germany, the German DRG statistic has proved as a useful tool to generate valid data on both (diagnoses-related) inpatient rates as well as the distribution of (OPS code-related) treatment modalities such as i.v. thrombolysis, mechanical thrombectomy, or ICU- and SU-care [8, 18], because correct and complete coding of both DRG- and OPS-codes is a prerequisite for reimbursement. While comprehensiveness of data is facilitated hereby, false economic incentives can be triggered. The German DRG-system is closely guarded, though, by a specialized medical service of the public health insurance system to avoid false coding. We therefore believe that most of the limitations discussed for administrative coding data (16) do not apply to the German system. Another inherent limitation, however, is the limitation to cases coded as such. Considering early transfers between hospitals in the first few hours, cases are considered as a transfer once they are coded as inpatient cases in the primary hospital (so called “hourly cases”). If they are not coded as an “inpatient” but only as an “outpatient” case, they will not appear as a transfer in the dataset, but as a regularly inpatient case of the secondary hospital. Regulatory rules provide the first mentioned proceeding even though it is unknown if all hospitals claim this proceeding. Therefore, transfer rates might be underestimated. However, we believe that due to reimbursement reasons every hospital has an inherent motivation to code these patients as “inpatient” cases. It can further be speculated if decreasing rates of early transfer rates as displayed may reflect improved allocation strategies of regional alliances between hospitals and emergency services, resulting in fewer necessary secondary transfers. Furthermore, our analysis is restricted to hospitalized cases only and cannot differentiate between first-ever and recurrent stroke. However, it is known that administrative data may result in an underestimation of disease incidence . Further limitations include, e.g., the lack of data on stroke severity, vascular risk factors, medications, or functional outcome. Also, ethnicity, neuroimaging status, and other individual items cannot be accounted for due to the strict anonymization of the data set.
Our analyses provide genuine insights in the treatment and care reality in German hospitals. This is due to the fact that treatments on specialized wards like SU and ICU are separately reimbursed once coded in the system. Even though special requirements are to be fulfilled, it can be assumed that reimbursement is an effective incentive to provide any specialized treatment modality. We have formerly reported on treatment rates of systemic thrombolysis and mechanical thrombectomy in ischemic stroke and were able to show, that both rates have continuously risen in the past years to rates of 15.9 and 5.8% in 2017 [8, 14]. Treatment rates on specialized units also increased over the observed time period. The demonstrated numbers illustrate that SU treatment is not limited to ischemic strokes alone and that the care reality reflects the according recommendations of the professional societies. In Germany, currently there are more than 325 SUs certified by the German stroke society with a constant rise over the last 20 years . One reason was the nationwide implementation of systemic thrombolysis and mechanical thrombectomy during this time period [8, 14]. AIS patients therefore are increasingly transferred to another hospital in the acute phase of treatment, mostly for interventional treatment. In order to guarantee for a comprehensive ability for interventional therapy over the country it is fundamental to provide a close net of SUs also in rural areas that can select patients qualifying for interventional therapy. This is partly met by networks encompassing “other stroke units” (i.e., not run by a neurological department), where neurological and neuro-radiological expertise are established by tele-medicine. We therefore hypothesized, that the amount of treatments on “other stroke units” should have increased in the observed time period. This has only been the case until 2014. We believe that this putative stagnation illustrates, that hospitals with formerly “other stroke units” have established a neurological department in the meantime.
Our data provide important information on the development and trends in stroke care in Germany. These insights are essential for future adjustments of infrastructure for inpatient stroke care. As recommended by the professional societies, increasing numbers of stroke patients are treated on specialized units like certified stroke units or ICUs. In AIS, the increasing portfolio of therapeutic options like systemic thrombolysis and mechanical thrombectomy illustrates the need to improve access to specialized care. Therefore, our data mandate future efforts to further increase the proportion of stroke patients admitted to specialized units.
International Statistical Classification of Diseases and Related Health Problems 10th revision, German modification
The German coding system and the ICD version remained unchanged during the analyzed time period except for implementation of the OPS code 8-98f for elaborated intensive care in 2013. Until 2012, all patients treated on an intensive care unit were coded with OPS 8–980.
Only few (< 600 per year) children and adolescents < 20 years were hospitalized for TIA or stroke between 2011 and 2017 and therefore excluded from statistical analysis.
Including G45.3 (amaurosis fugax) and G45.4 (transient global amnesia); G45.3 accounted for about 3.000 cases and G45.4 for about 7.000 cases.
We thank the Federal Statistical Office, department H1, for support in data collection. AHK has been supported by a European Academy of Neurology Research Fellowship.
All authors conceptualized the study. JE drafted the first manuscript version. DB, RW, AHK and CK performed statistical analysis. CW and WH revised the first draft. The final draft was revised by all authors. All authors approved the submission.
The authors received no financial support for this study.
Ethics approval and consent to participate
Data-sets used for this analysis were completely anonymized data provided by the German federal statistical office (DRG-statistic, www.destatis.de) in compliance with the German data protection regulations. These Data are publicly accessible in general. However, the original DRG raw data by Destatis in the data complexity analyzed here are not publicly visible and need to be obtained as paid service for users as either zip- or access-data file (https://www.destatis.de/DE/Service/Kontakt/Kontakt.html). Since there was no access to any individualized patient data whatsoever, no informed patient consent or ethical approval was needed for this study.
Consent for publication
JE has received travel grants from Daiichi-Sankyo and Bayer Vital and grants for the realization of scientific meetings by Bayer Health Care, Boehringer Ingelheim, Sanofi Aventis, and Pfizer. DB has received orders for analysis of the G-DRG system from Boehringer Ingelheim. RW has received speaker honoria from Medtronic/Covidien and Bristol Myers Squibb, and from serving on a scientific advisory board of Medtronic. AHK reports no disclosures. CW has received speaker and consultancy honoraria from Alexion, Amgen, Bayer-Schering. WH has received speaker and consultancy honoraria from Boehringer Ingelheim, Medtronic, Cerenovus and a research grant to perform ECASS4 from Boehringer Ingelheim. CK has received speaker honoraria and/or travel grants for scientific meetings from Bayer Vital, Boehringer-Ingelheim, and Daichii-Sankyo.
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