Abstract
Background
Studies from Denmark and the USA have shown differences in treatment outcomes for patients with peripheral arterial occlusive disease (PAOD) between hospitals of different size and certification status. For Germany, it is not known whether certification as a specialist center for vascular diseases or hospital size is associated with differences in the primary treatment outcome.
Methods
Using data from the German Federal Statistical Office, all hospitalizations due to PAOD of Fontaine stage IIb or higher were included in our study and the hospitals were classified according to their size and certification status. PAOD stage, age, sex, and comorbidities were documented for each hospitalization. Univariate and multivariate logistic regressions were performed to identify independent variables that predict various treatment endpoints.
Results
A total of 558 785 hospitalizations were included for analysis, of which 29% were in hospitals with certified vascular centers. In multivariate analysis, admissions to certified hospitals were associated with lower rates of major amputation (odds ratio [OR] 0.95, 95% confidence interval [0.92; 0.98], p = 0.003) and higher rates of minor amputation (OR 1.04 [1.01; 1.06], p = 0.004) with no difference observed in mortality (OR 0.99 [0.96; 1.03], p = 0.791). Admissions to larger hospitals were associated with more comorbidities, longer hospital stays, and higher rates of mortality and amputations.
Conclusion
Treatments in certified hospitals are associated with fewer major and more minor amputations. This may reflect intensification of therapy targeting preservation of functional limbs.
Peripheral arterial occlusive disease (PAOD) affects over 100 million people worldwide, resulting in over half a million years lived in disability each year (1). Advanced stages of PAOD are associated with increasing numbers of hospitalizations, revascularization procedures, and amputations as well as higher rates of mortality (2– 4). Several factors may influence in-hospital treatment outcomes, including disease-specific care certifications (DSCC) and hospital size (5– 9).
The number of different DSCC has risen sharply over the past few years, but only a small number of studies have yet analyzed the effect of DSCC on primary treatment outcomes (10). Although better outcomes of inpatient treatment have been reported in certified hospitals for patients with stroke or acute myocardial infarction (11– 15), the impact of certification status on the inpatient treatment of patients with PAOD has remained unclear.
As a second factor, hospital size has been demonstrated to correlate with in-hospital mortality and the rate of readmission, both in patients with chronic limb ischemia and in the general clinical context (7, 16, 17). Although this may be attributed to increased treatment complexity, there is a lack of data on other factors, such as a higher proportion of more advanced stages or a higher rate of comorbidity in the patient cohort, that may contribute to this observation (16).
In this study we therefore aimed to analyze differences in the treatment outcomes between hospitals of different size and different certification status. Furthermore, we sought to find out whether these two variables are independently associated with differences in amputation rates and in-hospital mortality.
Methods
Data source
Data on inpatient treatments in the years 2016–2018 were supplied by the German Federal Statistical Office (Destatis) (20). The detailed process of data acquisition has been reported previously (21). In brief, the authors wrote syntaxes in R (version 4.0.4; www.r-project.org/) using data structure files that were provided. After the syntaxes had been run over the raw data by Destatis using a controlled remote data processing method, the anonymized results were checked for confidentiality and then sent to the authors.
Patient cohort
All hospitalizations from 2016 to 2018 with PAOD of the lower extremity as the main diagnosis were included. The following codes of the International Classification of Diseases and Related Health Problems, 10th Revision (ICD-10) were used to this end: I70.22: pain-free walking distance < 200 m (Fontaine IIb, Rutherford 2–3); I70.23: pain at rest (Fontaine III, Rutherford 4); I70.24: minor tissue loss with ulceration (Fontaine IV, Rutherford 5); I70.25: major tissue loss with gangrene (Fontaine IV, Rutherford 6).
Hospital data
Hospitals were identified based on their institution code number and grouped according to their level of care. This is defined by the number of beds, based on a non-standardized but widely used classification system for hospital size in Germany: minimum care (< 100 beds), basic care (100–299 beds), standard care (300–499 beds), central or specialized care (500–799 beds) and maximum care (≥800 beds). Not included in this classification were specialized hospitals that predominantly treat patients with vascular diseases and possess distinct expertise regardless of the number of hospital beds. Because of their expertise and the low number of beds, these specialized hospitals were excluded from the analysis of the effect of hospital size on treatment outcome. Moreover, the existence of vascular disease-specific certification by the German Society of Interventional Radiology (DeGIR), the German Society for Vascular Surgery (DGG), or the German Society for Angiology (DGA) according to the announcements on the respective homepages was assessed (as of May 2020). To minimize changes in certification status over time, we limited the observation period to the years 2016–2018.
Statistical analysis
The data were analyzed using R version 4.0.4 (www.r-project.org/) and are presented as absolute numbers with percentages, as mean ± standard deviation (SD), or as median with interquartile range (IQR). Using secondary diagnoses, Elixhauser comorbidity groups were determined and the weighted linear van Walraven score was calculated using the R package comorbidity (www.cran.r-project.org/package=comorbidity) (22). Univariate and multivariate binomial logistic regression analyses were performed to assess the influence of different variables on the primary in-hospital treatment outcomes. The results are presented as odds ratios (OR) with 95% confidence intervals (95% CI). In multivariable regression analyses, the OR were adjusted for all independent variables (PAOD stage, age, sex, hypertension, type 2 diabetes mellitus, dyslipidemia, hospital size, and certification status) in the respective models. To ascertain the effect of the multiple admissions, multivariate analyses were also performed at 3-month intervals. Nagelkerke’s pseudo-R² was calculated to assess model performance.
Results
Status quo of PAOD in Germany (2016–2018)
A total of 558 785 inpatient treatments were included, spread over 881 (45.4%) of 1942 German hospitals. The mean age was 71.8±11.1 years, and 63.1% of the patients (352 571) were male. The median length of hospital stay was 6 days (IQR 2–12), and the overall in-hospital mortality was 2.6%. Major and minor amputations of the lower extremity were performed in 3.6% and 8.1% of hospitalizations, respectively. The proportions of hospitalizations with PAOD stages Fontaine IIb, III, IV with ulcers, and IV with gangrene were 46.9%, 12.3%, 20.5%, and 20.3%, respectively.
Differences between hospitals with and without certification for vascular diseases
A total of 126/881 treating hospitals (14.3%) were certified by at least one of the professional societies DGG, DGA, or DeGIR. Fifty (39.7%) were certified solely by the DGG, 42 (33.3%), by all three societies, 31 (24.6%) by the DGG and the DeGIR, and three (2.4%) by the DGG and the DGA. Certified hospitals admitted 7.8% more patients with Fontaine IIb (49.5% versus 45.9%) and thus treated a lower proportion of more advanced stages. In univariate analyses we observed lower rates of major amputations (3.3% vs. 3.7%; OR 0.88 [0.86; 0.91], p < 0.001) and minor amputations (7.9% vs. 8.2%; OR 0.96 [0.94; 0.98], p < 0.001) overall in certified hospitals. However, certified hospitals carried out more minor amputations on patients hospitalized with Fontaine stage IV (7.8% vs. 7.5 % for Fontaine IV with ulcers, 33.2% vs. 31.8 % for Fontaine IV with gangrene) (table 1).
Table 1. Characteristics of inpatient PAOD treatments in certified and non-certified hospitals (2016–2018).
|
Certified
(n = 162 401; 29.1%) |
Non-certified
(n = 396 384; 70.9%) |
All
(n = 558 785; 100%) |
|
| PAOD stage − Fontaine IIb − Fontaine III − Fontaine IVu − Fontaine IVg |
80 456 (49.5) 19 294 (11.9) 31 588 (19.5) 31 063 (19.1) |
181 774 (45.9) 49 460 (12.5) 83 008 (20.9) 82 142 (20.7) |
262 230 (46.9) 68 754 (12.3) 114 596 (20.5) 113 205 (20.3) |
| Age in years | 71.4 ± 11.0 | 72.0 ± 11.1 | 71.8 ± 11.1 |
| Male sex | 102 524 (63.1) | 250 113 (63.1) | 352 637 (63.1) |
| Hospital stay in days | 6 (2–12) | 6 (2–12) | 6 (2–12) |
| van Walraven score | 5 (2–10) 6.9 ± 6.5 |
6 (2–11) 7.2 ± 6.7 |
5 (2–11) 7.1 ± 6.7 |
| Hypertension | 110 072 (67.8) | 265 985 (67.1) | 376 057 (67.3) |
| Type 2 diabetes mellitus | 53 562 (33.0) | 135 284 (34.1) | 188 842 (33.8) |
| Dyslipidemia | 71 827 (44.2) | 158 777 (40.1) | 230 604 (41.3) |
| In-hospital mortality − Fontaine IIb − Fontaine III − Fontaine IVu − Fontaine IVg |
4043 (2.5) 176 (2.2) 416 (2.2) 1052 (3.3) 2399 (7.7) |
10 487 (2.6) 457 (2.6) 936 (1.9) 2803 (3.4) 6291 (7.7) |
14 530 (2.6) 633 (2.4) 1352 (2.0) 3855 (3.4) 8690 (7.7) |
| Major amputations − Fontaine IIb − Fontaine III − Fontaine IVu − Fontaine IVg |
5 309 (3.3) 14 (0.0) 263 (1.4) 810 (2.6) 4222 (13.6) |
14 599 (3.7) 69 (0.0) 699 (1.4) 2077 (2.5) 11 754 (14.3) |
19 908 (3.6) 83 (0.0) 962 (1.4) 2887 (2.5) 15 976 (14.1) |
| Minor amputations − Fontaine IIb − Fontaine III − Fontaine IVu − Fontaine IVg |
12 890 (7.9) 34 (0.0) 59 (0.3) 2474 (7.8) 10 323 (33.2) |
32 640 (8.2) 74 (0.0) 161 (0.3) 6260 (7.5) 26 145 (31.8) |
45 530 (8.1) 108 (0.0) 220 (0.3) 8734 (7.6) 36 468 (32.2) |
The data are presented as n (%), mean ± standard deviation, and/or median (interquartile range). For in-hospital mortality, major amputations, and minor amputations, the proportions given for the different stages of PAOD relate to the total number in each stage
IVg, Stage IV with gangrene; IVu, stage IV with ulceration; PAOD peripheral arterial occlusive disease
Differences between hospitals of different sizes
Most PAOD patients (74.2%) were admitted to hospitals with ≥300 beds (standard care: 27.1%; central or specialized care: 25.3%; maximum care: 21.8%). The hospital stay was longer in larger hospitals (range: from 3 days [IQR 2–9] in hospitals offering minimum care to 7 days [IQR 2–13] in those providing central care), where patients also showed increased comorbidities as reflected by a higher van Walraven score (range: from 2 [IQR 2–7] in minimum care to 7 [IQR 2–12] in maximum care hospitals). The proportion of admissions at more advanced PAOD stages (from Fontaine stage III) was greater in larger hospitals (e.g., 42.5% Fontaine stage IV in maximum care vs. 34.9% in minimum care), where also proportionally more major and minor amputations were performed. Data were not available for 3.3% of hospitalizations, most likely due to hospital closures. The detailed distribution of data by level of care is presented in Table 2. There is a positive association between hospital size and proportion of certifications. Of the hospitals with < 100 and 100–299 beds, only 2.4% and 4.3% were certified, against 15.3%, 24.8%, and 30.8% for hospitals with 300–499, 500–799, and ≥ 800 beds, respectively.
Table 2. Characteristics of inpatient PAOD treatments according to hospital size (2016–2018).
|
Care level No. of beds No. of hospitals |
Minimum
care < 100 (n = 42) |
Basic care
100–299 (n = 324) |
Standard care
300–499 (n = 229) |
Central care
500–799 (n = 161) |
Maximum care
≥ 800 (n = 104) |
Specialized hospitals
(n = 25) |
ND |
| Number (% of all cases) | 6820 (1.2) | 102 964 (18.4) | 151 155 (27.1) | 141 562 (25.3) | 122 085 (21.8) | 15 924 (2.8) | 18 275 (3.3) |
| Fontaine IIb | 3839 (56.3) | 47 092 (45.7) | 72 335 (47.9) | 67 754 (47.9) | 54 889 (45.0) | 8929 (56.1) | 7392 (40.4) |
| Fontaine III | 598 (8.8) | 13 443 (13.1) | 18 283 (12.1) | 17 590 (12.4) | 15 260 (12.5) | 1 472 (9.2) | 2108 (11.5) |
| Fontaine IVu | 1108 (16.2) | 21 904 (21.3) | 30 328 (20.1) | 26 838 (19.0) | 26 638 (21.8) | 3 73 (23.1) | 4107 (22.5) |
| Fontaine IVg | 1275 (18.7) | 20 525 (19.9) | 30 209 (20.0) | 29 380 (20.8) | 25 298 (20.7) | 1850 (11.6) | 4668 (25.5) |
| Age in years | 71.8 ± 10.9 | 72.3 ± 11.0 | 71.8 ± 11.0 | 71.7 ± 11.0 | 71.3 ± 11.1 | 71.4 ± 10.7 | 72.6 ± 11.2 |
| Male sex | 4206 (61.7) | 64 286 (62.4) | 94 870 (62.8) | 88 661 (62.6) | 78 816 (64.6) | 10 206 (64.1) | 11 526 (63.1) |
| Hospital stay in days | 3 (2–9) | 6 (2–11) | 6 (2–12) | 7 (2–13) | 6 (2–13) | 4 (2–10) | 7 (2–12) |
| van Walraven score | 2 (2–7) | 5 (2–10) | 5 (2–10) | 6 (2–11) | 7 (2–12) | 6 (2–10) | 7 (2–12) |
| In-hospital mortality | 92 (1.3) | 2445 (2.4) | 3959 (2.6) | 3929 (2.8) | 3347 (2.7) | 168 (1.1) | 590 (3.2) |
| Major amputations − Fontaine IIb − Fontaine III − Fontaine IVu − Fontaine IVg |
171 (2.5) < 5 < 5 16 (1.4) 151 (11.8) |
3672 (3.6) 15 (0.0) 179 (1.3) 462 (2.1) 3016 (14.7) |
5 398 (3.6) 18 (0.0) 260 (1.4) 828 (2.7) 4292 (14.2) |
5148 (3.6) 23 (0.0) 251 (1.4) 748 (2.8) 4126 (14.0) |
4442 (3.6) 23 (0.0) 222 (1.5) 682 (2.6) 3515 (13.9) |
245 (1.5) < 5 22 (1.5) 46 (1.3) 176 (9.5) |
832 (4.6) < 5 24 (1.1) 105 (2.6) 700 (15.0 |
| Minor amputations − Fontaine IIb − Fontaine III − Fontaine IVu − Fontaine IVg |
368 (5.4) < 5 < 5 51 (4.6) 315 (24.7) |
8082 (7.8) 23 (0.0) 37 (0.3) 1609 (7.3) 6413 (31.2) |
12 646 (8.4) 30 (0.0) 59 (0.3) 2486 (8.2) 10 071 (33.3) |
11 967 (8.5) 32 (0.0) 49 (0.3) 2195 (8.2) 9691 (33.0) |
10 252 (8.4) 17 (0.0) 56 (0.4) 1922 (7.2) 8257 (32.6) |
522 (3.3) < 5 < 5 184 (5.0) 333 (18.0) |
1693 (9.3) < 5 15 (0.7) 287 (7.0) 1388 (29,7) |
The data are presented as n (%), mean ± standard deviation, and/or median (interquartile range). IVg, Stage IV with gangrene; IVu, stage IV with ulceration; ND, no data available; PAOD, peripheral arterial occlusive disease
Multivariate analyses
The multivariate analyses showed no difference in in-hospital mortality between certified and uncertified hospitals (OR 0.99 [0.96; 1.03], p = 0.791). In certified hospitals we observed a lower rate of major amputations (OR 0.95 [0.92; 0.98], p = 0.003) and a higher rate of minor amputations (OR 1.04 [1.01; 1.06], p = 0.004). We also observed these tendencies in quarterly analyses for major amputations (range of OR: 0.89–0.99) and minor amputations (range of OR: 1.03–1.07); however, the range of uncertainty was wider due to the inevitable smaller number of hospitalizations in these analyses (all p > 0.05).
With regard to hospital size, we observed lower rates of in-hospital mortality in smaller hospitals (basic care and minimum care) than in hospitals offering maximum care (OR 0.81 [0.77; 0.86] and OR 0.49 [0.39; 0.60]; both p < 0.001). Minimum care hospitals (< 100 beds) showed lower rates of both major (OR 0.75 [0.64–0.88], p < 0.001) and minor amputations (OR 0.69 [0.61–0.77], p < 0.001) than maximum care hospitals. Detailed data of the multivariate analyses are presented in Tables 3– 5, and the eTable shows the results of the quarterly analyses.
Table 3. Univariate and multivariate analyses of in-hospital mortality among inpatients treated for PAOD (2016–2018).
| In-hospital mortality | Univariate analysis |
Multivariate analysis
(Nagelkerke’s pseudo-R²: 0.174) |
||
| Odds ratio | p-value | Odds ratio | p-value | |
| PAOD stage − Fontaine IIb (ref) − Fontaine III − Fontaine IVu − Fontaine IVg |
1.00 8.29 [7.54; 9.11] 14.39 [13.22; 15.65] 34.36 [31.69; 37.26] |
< 0.001 < 0.001 < 0.001 |
1.00 6.80 [6.19; 7.48] 9.52 [8.74; 10.38] 22.42 [20.64; 24.35] |
< 0.001 < 0.001 < 0.001 |
| Age (continuous) | 1.07 [1.07; 1.08] | < 0.001 | 1.04 [1.04; 1.05] | < 0.001 |
| Sex − male (ref) − female |
1.00 1.28 [1.23; 1.32] |
< 0.001 |
1.00 0.98 [0.94; 1.01] |
0.176 |
| Hypertension | 0.57 [0.55; 0.59] | < 0.001 | 0.64 [0.62; 0.66] | < 0.001 |
| Type 2 diabetes mellitus | 1.31 [1.26; 1.35] | < 0.001 | 1.02 [0.98; 1.05] | 0.325 |
| Dyslipidemia | 0.44 [0.42; 0.46] | < 0.001 | 0.67 [0.65; 0.70] | < 0.001 |
| Care level − Maximum care (≥ 800) (ref) − Central care (500–799) − Standard care (300–499) − Basic care (100–299) − Minimum care (< 100) |
1.00 1.01 [0.97; 1.06] 0.95 [0.91; 1.00] 0.86 [0.82; 0.91] 0.49 [0.39; 0.60] |
0.596 0.049 < 0.001 < 0.001 |
1.00 1.00 [0.95; 1.05] 0.96 [0.91; 1.01] 0.81 [0.77; 0.86] 0.49 [0.39; 0.60] |
0.895 0.092 < 0.001 < 0.001 |
| Certification status − Not certified (ref) − Certified |
1.00 0.94 [0.91; 0.97] |
< 0.001 |
1.00 0.99 [0.96; 1.03] |
0.791 |
The odds ratios are given with their 95% confidence intervals. In the multivariate analysis they were adjusted for all variables (PAOD stage, age, sex, hypertension, type 2 diabetes mellitus, dyslipidemia, care level, and certification status).
IVg, Stage IV with gangrene; IVu, stage IV with ulceration; ref, reference; PAOD, peripheral arterial occlusive disease
eTable. Quarterly multivariate analyses for in-hospital mortality and amputations among inpatients treated for PAOD.
| Quarter | 2016-2 | 2016-3 | 2017-2 | 2017-3 | 2018-2 | 2018-3 | ||||||
| Inpatient cases (n) | 48 445 | 47 311 | 47 023 | 47 046 | 47 852 | 45 955 | ||||||
| Odds ratio | p-value | Odds ratio | p-value | Odds ratio | p-value | Odds ratio | p-value | Odds ratio | p-value | Odds ratio | p-value | |
| In-hospital mortality | ||||||||||||
| PAOD stage III | 6.18 [4.47; 8.54] | < 2e, 16 | 8.04 [5.80; 11.16] | < 2e, 16 | 6.84 [4.75; 9.84] | < 2e, 16 | 8.42 [6.00; 11.81] | < 2e, 16 | 6.51 [4.66; 9.09] | < 2e, 16 | 7.96 [5.64; 11.23] | < 2e, 16 |
| pPAOD stage IVg | 20.06 [15.17; 26.53] |
< 2e, 16 | 25.69 [19.24; 34.30] |
< 2e, 16 | 25.26 [18.45; 34.57] |
< 2e, 16 | 26.66 [19.75. 35.98] |
< 2e, 16 | 20.30 [15.24; 27.04] |
< 2e, 16 | 24.46 [18.08; 33.08] |
< 2e, 16 |
| PAOD stage IVu | 9.44 [7.07; 12.60] | < 2e, 16 | 10.25 [7.60; 13.84] | < 2e, 16 | 10.80 [7.80; 14.95] | < 2e, 16 | 10.95 [8.03; 14.95] | < 2e, 16 | 9.36 [6.94; 12.60] | < 2e, 16 | 9.84 [7.18; 13.47] | < 2e, 16 |
| Age in years | 1.04 [1.03; 1.05] | < 2e, 16 | 1.04 [1.03; 1.05] | < 2e, 16 | 1.05 [1.04; 1.06] | < 2e, 16 | 1.05 [1.04; 1.05] | < 2e, 16 | 1.04 [1.03; 1.05] | < 2e, 16 | 1.04 [1.03; 1.05] | < 2e, 16 |
| Sex, female | 1.04 [0.92; 1.18] | 0.4892 | 0.98 [0.87; 1.11] | 0.7824 | 0.88 [0.78; 1.00] | 0.0493 | 0.96 [0.84; 1.09] | 0.5110 | 1.06 [0.93; 1.20] | 0.3892 | 0.92 [0.80; 1.05] | 0.2066 |
| Basic care | 0.87 [0.72; 1.06] | 0.1718 | 0.75 [0.62; 0.92] | 0.0052 | 0.86 [0.71; 1.04] | 0.1202 | 0.88 [0.72; 1.08] | 0.2101 | 0.67 [0.55; 0.81] | 0.0000 | 0.77 [0.62; 0.95] | 0.0155 |
| Minimum care | 0.43 [0.19; 0.98] | 0.0447 | 0.57 [0.28; 1.17] | 0.1245 | 0.55 [0.28; 1.10] | 0.0914 | 0.81 [0.43; 1.52] | 0.5163 | 0.56 [0.28; 1.10] | 0.0918 | 0.23 [0.07; 0.71] | 0.0114 |
| Standard care | 1.00 [0.84; 1.18] | 0.9908 | 1.10 [0.93; 1.30] | 0.2632 | 0.95 [0.80; 1.12] | 0.5175 | 0.96 [0.81; 1.15] | 0.6891 | 0.85 [0.72; 1.00] | 0.0569 | 1.03 [0.86; 1.24] | 0.7431 |
| Central care | 1.03 [0.87; 1.21] | 0.7674 | 0.95 [0.80; 1.13] | 0.5838 | 1.02 [0.86; 1.21] | 0.7956 | 1.13 [0.95; 1.35] | 0.1558 | 0.87 [0.73; 1.03] | 0.1022 | 1.04 [0.86; 1.25] | 0.7004 |
| Certified | 0.98 [0.86; 1.13] | 0.8076 | 1.00 [0.87; 1.14] | 0.9472 | 0.93 [0.81; 1.06] | 0.2856 | 1.16 [1.01; 1.33] | 0.0324 | 0.87 [0.76; 1.00] | 0.0567 | 0.93 [0.81; 1.08] | 0.3650 |
| Hypertension | 0.55 [0.49; 0.62] | < 2e, 16 | 0.66 [0.58; 0.74] | 0.0000 | 0.72 [0.64; 0.81] | 0.0000 | 0.64 [0.57; 0.73] | 0.0000 | 0.65 [0.58; 0.74] | 0.0000 | 0.74 [0.64; 0.84] | 0.0000 |
| Type 2 diabetes mellitus | 1.06 [0.94; 1.20] | 0.3134 | 0.98 [0.87; 1.11] | 0.7871 | 1.18 [1.04; 1.33] | 0.0078 | 0.97 [0.85; 1.10] | 0.5905 | 0.99 [0.87; 1.12] | 0.8616 | 1.00 [0.88; 1.15] | 0.9713 |
| Dyslipidemia | 0.66 [0.57; 0.76] | 0.0000 | 0.69 [0.60; 0.79] | 0.0000 | 0.78 [0.68; 0.90] | 0.0004 | 0.69 [0.60; 0.80] | 0.0000 | 0.66 [0.57; 0.76] | 0.0000 | 0.62 [0.53; 0.72] | 0.0000 |
| Nagelkerke’s pseudo-R² | 0.17067153 | 0.1796869 | 0.17626055 | 0.1887138 | 0.1648561 | 0.17367796 | ||||||
| Major amputations | ||||||||||||
| PAOD stage III | 28.80 [14.89; 55.71] |
< 2e, 16 | 62.28 [27.26; 142.29] |
< 2e, 16 | 40.97 [19.82; 84.68] |
< 2e, 16 | 30.02 [15.49; 58.19] |
< 2e, 16 | 38.58 [18.61; 80.01] |
< 2e, 16 | 72.57 [26.45; 199.14] |
< 2e, 16 |
| pPAOD stage IVg | 372.41 [199.49; 695.22] |
< 2e, 16 | 746.30 [334.30; 1666.09] | < 2e, 16 | 442.74 [220.55; 888.79] | < 2e, 16 | 432.01 [231.40; 806.54] | < 2e, 16 | 460.26 [229.27; 923.97] | < 2e, 16 | 1002.32 [374.98; 2679.18] | < 2e, 16 |
| PAOD stage IVu | 62.36 [33.10; 117.48] |
< 2e, 16 | 116.48 [51.82; 261.82] | < 2e, 16 | 69.93 [34.49; 141.76] | < 2e, 16 | 65.23 [34.59; 123.00] | < 2e, 16 | 74.72 [36.87; 151.41] | < 2e, 16 | 165.64 [61.58; 445.49] | < 2e, 16 |
| Age in years | 1.00 [0.99; 1.00] | 0.2148 | 0.99 [0.99; 1.00] | 0.0314 | 1.00 [0.99; 1.00] | 0.0469 | 1.00 [0.99; 1.00] | 0.1972 | 1.00 [0.99; 1.00] | 0.0576 | 0.99 [0.99; 1.00] | 0.0344 |
| Sex, female | 0.97 [0.87; 1.08] | 0.5727 | 1.03 [0.93; 1.15] | 0.5858 | 0.92 [0.83; 1.03] | 0.1547 | 0.98 [0.88; 1.09] | 0.6960 | 0.89 [0.80; 0.99] | 0.0398 | 0.95 [0.84; 1.07] | 0.3904 |
| Basic care | 1.16 [0.98; 1.36] | 0.0773 | 0.96 [0.82; 1.13] | 0.6116 | 1.19 [1.01; 1.40] | 0.0407 | 1.06 [0.90; 1.25] | 0.4826 | 0.97 [0.82; 1.15] | 0.7329 | 1.09 [0.91; 1.29] | 0.3408 |
| Minimum care | 0.75 [0.41; 1.38] | 0.3552 | 0.80 [0.47; 1.37] | 0.4171 | 0.83 [0.49; 1.41] | 0.4937 | 1.00 [0.61; 1.66] | 0.9848 | 0.85 [0.49; 1.50] | 0.5858 | 0.67 [0.36; 1.26] | 0.2112 |
| Standard care | 1.10 [0.95; 1.28] | 0.1948 | 0.92 [0.80; 1.06] | 0.2683 | 1.12 [0.97; 1.30] | 0.1255 | 1.06 [0.91; 1.23] | 0.4601 | 1.05 [0.91; 1.21] | 0.5207 | 1.11 [0.95; 1.30] | 0.1870 |
| Central care | 1.00 [0.86; 1.16] | 0.9876 | 0.98 [0.85; 1.13] | 0.8002 | 1.15 [0.99; 1.34] | 0.0679 | 1.02 [0.88; 1.19] | 0.7992 | 1.14 [0.99; 1.32] | 0.0770 | 1.15 [0.98; 1.34] | 0.0809 |
| Certified | 0.97 [0.86; 1.09] | 0.5887 | 0.96 [0.85; 1.08] | 0.4909 | 0.94 [0.83; 1.05] | 0.2788 | 0.89 [0.79; 1.00] | 0.0516 | 0.97 [0.86; 1.09] | 0.5859 | 0.99 [0.90; 1.10] | 0.7796 |
| Hypertension | 0.81 [0.73; 0.89] | 0.0000 | 0.96 [0.86; 1.06] | 0.4171 | 0.85 [0.76; 0.94] | 0.0021 | 0.87 [0.79; 0.97] | 0.0145 | 1.00 [0.90; 1.11] | 0.9705 | 0.96 [0.85; 1.07] | 0.4438 |
| Type 2 diabetes mellitus | 0.96 [0.86; 1.06] | 0.3869 | 0.95 [0.86; 1.05] | 0.3148 | 0.94 [0.85; 1.05] | 0.2644 | 0.95 [0.86; 1.06] | 0.3477 | 0.91 [0.82; 1.01] | 0.0886 | 0.90 [0.81; 1.01] | 0.0667 |
| Dyslipidemia | 0.86 [0.77; 0.97] | 0.0118 | 0.89 [0.79; 0.99] | 0.0359 | 0.95 [0.85; 1.06] | 0.3476 | 0.85 [0.76; 0.96] | 0.0068 | 0.89 [0.80; 1.00] | 0.0482 | 0.81 [0.72; 0.91] | 0.0004 |
| Nagelkerke’s pseudo-R² | 0.27059174 | 0.28977066 | 0.26567701 | 0.29268269 | 0.26752094 | 0.28769807 | ||||||
| Minor amputations | ||||||||||||
| PAOD stage III | 10.35 [4.05; 26.44] | 0.0000 | 9.82 [4.49; 21.44] | 0.0000 | 8.34 [3.77; 18.46] | 0.0000 | 10.07 [4.81; 21.08] | 0.0000 | 6.62 [2.74; 15.98] | 0.0000 | 4.04 [1.78; 9.16] | 0.0008 |
| pPAOD stage IVg | 1763.30 [791.05; 3930.52] |
< 2e, 16 | 1312.51 [681.16; 2529.03] |
< 2e, 16 | 1140.29 [591.96; 2196.57] |
< 2e, 16 | 1098.17 [589.32; 2046.37] |
< 2e, 16 | 1360.36 [678.92; 2725.75] |
< 2e, 16 | 929.41 [526.20; 1641.58] |
< 2e, 16 |
| PAOD stage IVu | 312.11 [139.70; 697.32] |
< 2e, 16 | 241.18 [124.87; 465.85] |
< 2e, 16 | 205.09 [106.15; 396.23] |
< 2e, 16 | 197.33 [105.58; 368.82] |
< 2e, 16 | 241.75 [120.33; 485.69] |
< 2e, 16 | 167.96 [94.79; 297.61] |
< 2e, 16 |
| Age in years | 1.00 [0.99; 1.00] | 0.1559 | 1.00 [0.99; 1.00] | 0.0781 | 1.00 [1.00; 1.00] | 0.6729 | 1.00 [0.99; 1.00] | 0.4985 | 1.00 [1.00; 1.00] | 0.4372 | 1.00 [0.99; 1.00] | 0.5178 |
| Sex, female | 0.60 [0.56; 0.66] | < 2e, 16 | 0.55 [0.51; 0.60] | < 2e, 16 | 0.57 [0.52; 0.62] | < 2e, 16 | 0.60 [0.55; 0.65] | < 2e, 16 | 0.59 [0.54; 0.64] | < 2e, 16 | 0.59 [0.54; 0.65] | < 2e, 16 |
| Basic care | 0.98 [0.87; 1.11] | 0.7561 | 1.05 [0.93; 1.19] | 0.4062 | 1.04 [0.93; 1.18] | 0.4746 | 0.89 [0.78; 1.01] | 0.0686 | 0.95 [0.85; 1.07] | 0.3867 | 0.96 [0.85; 1.09] | 0.5680 |
| Minimum care | 0.74 [0.48; 1.15] | 0.1810 | 0.60 [0.38; 0.95] | 0.0276 | 0.66 [0.45; 0.98] | 0.0408 | 0.52 [0.33; 0.82] | 0.0051 | 0.59 [0.38; 0.90] | 0.0154 | 0.63 [0.41; 0.97] | 0.0376 |
| Standard care | 1.10 [0.99; 1.22] | 0.0861 | 1.18 [1.06; 1.32] | 0.0026 | 1.10 [0.99; 1.22] | 0.0804 | 1.01 [0.90; 1.13] | 0.8585 | 1.02 [0.92; 1.13] | 0.7614 | 1.04 [0.93; 1.17] | 0.4849 |
| Central care | 1.10 [0.99; 1.23] | 0.0755 | 1.06 [0.95; 1.18] | 0.3125 | 1.11 [1.00; 1.24] | 0.0472 | 1.00 [0.89; 1.12] | 0.9937 | 0.99 [0.89; 1.10] | 0.8786 | 1.08 [0.96; 1.21] | 0.2012 |
| Certified | 1.07 [0.98; 1.16] | 0.1479 | 1.05 [0.96; 1.14] | 0.3006 | 1.04 [0.95; 1.13] | 0.3908 | 1.03 [0.94; 1.12] | 0.5556 | 1.05 [0.96; 1.14] | 0.2903 | 1.03 [0.94; 1.13] | 0.5022 |
| Hypertension | 1.03 [0.95; 1.11] | 0.4997 | 1.03 [0.95; 1.12] | 0.4075 | 1.05 [0.97; 1.14] | 0.2164 | 1.00 [0.92; 1.09] | 0.9792 | 1.09 [1.01; 1.18] | 0.0342 | 1.07 [0.99; 1.17] | 0.1025 |
| Type 2 diabetes mellitus | 1.37 [1.27; 1.47] | 0.0000 | 1.33 [1.23; 1.44] | 0.0000 | 1.22 [1.13; 1.31] | 0.0000 | 1.43 [1.32; 1.55] | < 2e, 16 | 1.33 [1.24; 1.43] | 0.0000 | 1.46 [1.35; 1.59] | < 2e, 16 |
| Dyslipidemia | 0.99 [0.91; 1.08] | 0.8381 | 1.04 [0.96; 1.13] | 0.3079 | 0.96 [0.88; 1.04] | 0.2926 | 0.97 [0.89; 1.06] | 0.4950 | 0.99 [0.92; 1.07] | 0.8060 | 1.04 [0.96; 1.13] | 0.3611 |
| Nagelkerke’s pseudo-R² | 0.4174419 | 0.4271354 | 0.4117935 | 0.4245308 | 0.4221647 | 0.4324692 | ||||||
The PAOD stages corrrespond to the Fontaine classification. The odds ratios are given with their 95% confidence intervals. They were adjusted for all variables (PAOD stage, age, sex, hypertension, type 2 diabetes mellitus, dyslipidemia, care level, and certification status).
IVg, Stage IV with gangrene; IVu, stage IV with ulceration; PAOD, peripheral arterial occlusive disease
Discussion
In this study we analyzed differences in the inpatient treatment outcomes of patients with PAOD with regard to hospital size and certification status in the years 2016–2018 in Germany. The most important findings are:
PAOD admissions to certified hospitals were associated with lower rates of major amputations and higher rates of minor amputations.
In multivariate analysis, we observed no differences in in-hospital mortality between hospitals with and without certification.
Larger hospitals received a larger proportion of the patients with advanced stages of PAOD, and admissions to smaller hospitals were associated with lower amputation rates and lower in-hospital mortality.
Although less than one sixth of the hospitals that admitted patients with PAOD were certified as vascular centers, these institutions cared for almost one third of the population.
As society is aging, the number of patients with PAOD and thus the number with more advanced stages in need of revascularization is rising (23– 25). Recently, several studies have analyzed the status and trends of inpatient care for patients with PAOD (16, 21, 23, 26– 28). Over the past decades the inpatient treatment of PAOD patients has gradually transitioned from open surgery to endovascular revascularization procedures, contributing to lower rates of amputation (e.g., reduction of major amputations from 5.5% to 3.5% in Germany between 2009 and 2018) and decreasing in-hospital mortality (down from 3.1% to 2.6% in Germany between 2009 and 2018) (21, 23, 26, 29, 30). This study also yields new insights into hospital-specific factors such as hospital size and certification status with regard to the characteristics and clinical outcome of patients with PAOD.
An increasing number of DSCC are available worldwide, covering both chronic illnesses (e.g., cancers and chronic cardiovascular disorders) and acute diseases (e.g., stroke and acute myocardial infarction), with the aim of assuring and indeed improving the quality of care (10– 13, 31– 33). To our knowledge there are no large-scale studies comparing the characteristics and clinical outcome of PAOD patients in hospitals with and without certified vascular centers. A Danish nationwide study analyzing a general cohort of over 270,000 inpatients reported lower 30-day mortality rates in accredited hospitals than in partially accredited hospitals (4.14% [4.00; 4.28] vs. 4.28% [4.20; 4.37]) (34). In our study, in contrast, we found no differences in in-hospital mortality between certified and non-certified hospitals. Although the univariable analyses pointed to such differences, this was not confirmed by multivariate analysis, which took account of other parameters such as PAOD stage, age and comorbidities. Furthermore, this discrepancy may be explained by the lack of differentiation between in-hospital mortality and 30-day mortality. The latter could not be established on the basis of the data available for analysis.
In a study comparing general treatment outcomes and readmission rates among 4.2 million patients in the USA with regard to the accreditation status of the treating hospitals, Lam et al. reported only slightly reduced readmission rates in accredited institutions while mortality did not differ significantly (9). Although we found differences in other characteristics such as age, sex, length of stay, and comorbidities, the certification status was not an independent predictor of in-hospital mortality. Strikingly, hospitals with certification for vascular diseases performed fewer major amputations and more minor amputations. These tendencies persisted in all quarterly analyses, although they did not always reach statistical significance due to smaller sample sizes. A reason for these differences in amputation rates may be more intensive therapy in certified hospitals with a focus on limb salvage, whereby minor amputations play a crucial role in preservation of limb function. It must be noted that a comprehensive evaluation of the quality of treatment in certified hospitals requires the evaluation of longitudinal data as quality cannot be judged solely on the basis of in-hospital mortality and amputation rates.
Reports on hospital size and hospital-specific treatment outcomes are scarce and divergent. A meta-analysis on mortality in the general clinical context revealed lower mortality rates in larger hospitals (OR 0.89 [0.85; 0.92]) (7). Agarwal et al. reported a positive correlation between hospital size and major amputation rate (OR 1.33 [1.23; 1.44]) for PAOD patients with chronic limb ischemia in the US (16). Looking at absolute rates, there are more major and minor amputations as well as increased in-hospital mortality in larger hospitals (≥ 500 beds). Besides the broader availability of surgical treatment options, this may also be attributable to transfers of patients in need of amputation from smaller to larger hospitals.
Strengths and limitations
The greatest limitation of this study is the lack of longitudinal data, meaning that it provides information on individual hospitalizations rather than individual patients. This introduces bias, because patients with multiple hospitalizations during the observation period were inevitably included more than once. To counter possible multiple inclusion of the same patients, we conducted quarterly analyses of our multivariable models to verify whether the trends observed over the entire study period could also be discerned for shorter periods with presumably lower readmission rates. A second limitation is that the status of hospital certification was determined after the analyzed period. If a hospital was certified during the observation period, all cases at this hospital over the entire observation period counted as treatments with certification. Because the certification process requires a certain experience and quality of the treatment procedures before the certificate is issued, however, it can be assumed that the level of care hardly changed during this period. Third, our study is limited by the fact that only mortality and amputations were investigated as primary treatment outcomes. The available data did not permit analysis of variables such as readmission rates, type of treatment, or patient satisfaction. Fourth, there remains the possibility that patients admitted to certified hospitals were not treated in the certified department, as PAOD is sometimes be treated by different specialties within a hospital, e.g., vascular surgery and cardiology, without cooperation being agreed. Finally, the dataset comprises administrative data collected to receive financial compensation for treatment procedures. Therefore, bias due to economic factors and motivations cannot be excluded.
Conclusion
This study suggests that the outcome of the inpatient treatment of patients with PAOD differs according to the certification status and size of the treating hospital. Treatment in certified hospitals is associated with a lower rate of major amputations and an increased rate of minor amputations. This may be attributable to intensification of therapy with the aim of preserving the function of the affected limb. Larger hospitals care for a higher proportion of patients with more advanced stages of PAOD, which are associated with more amputations and higher mortality.
Table 4. Univariate and multivariate analyses of major amputations among inpatients treated for PAOD (2016–2018).
| Major amputations | Univariate analysis |
Multivariate analysis
(Nagelkerke’s pseudo-R²: 0.270) |
||
| Odds ratio | p-value | Odds ratio | p-value | |
| PAOD stage − Fontaine IIb (ref) − Fontaine III − Fontaine IVu − Fontaine IVg |
1.00 44.82 [35.81; 56.09] 81.63 [65.62; 101.54] 518.97 [418.25; 643.94] |
< 0.001 < 0.001 < 0.001 |
1.00 45.09 [36.03; 56.44] 84.24 [67.70; 104.82] 526.09 [423.81; 653.06] |
< 0.001 < 0.001 < 0.001 |
| Age (continuous) | 1.03 [1.03; 1.03] | < 0.001 | 1.00 [0.99; 1.00] | < 0.001 |
| Sex − male (ref) − female |
1.00 0.94 [0.92; 0.97] |
< 0.001 |
1.00 0.96 [0.93; 0.99] |
0.012 |
| Hypertension | 0.73 [0.71; 0.76] | < 0.001 | 0.89 [0.87; 0.92] | < 0.001 |
| Type 2 diabetes mellitus | 1.48 [1.44; 1.53] | < 0.001 | 0.96 [0.93; 0.99] | 0.008 |
| Dyslipidemia | 0.58 [0.56; 0.60] | < 0.001 | 0.86 [0.83; 0.89] | < 0.001 |
| Care level − Maximum care (≥ 800) (ref) − Central care (500–799) − Standard care (300–499) − Basic care (100–299) − Minimum care (< 100) |
1.00 1.00 [0.96; 1.04] 0.98 [0.94; 1.02] 0.98 [0.94; 1.02] 0.68 [0.58; 0.80] |
0.979 0.348 0.360 < 0.001 |
1.00 1.02 [0.98; 1.06] 1.03 [0.99; 1.08] 1.00 [0.96; 1.05] 0.75 [0.64; 0.88] |
0.380 0.161 0.865 < 0.001 |
| Certification status − Not certified (ref) − Certified |
1.00 0.88 [0.86; 0.91] |
< 0.001 |
1.00 0.95 [0.92; 0.98] |
0.003 |
The odds ratios are given with their 95% confidence intervals. In the multivariate analysis they were adjusted for all variables (PAOD stage, age, sex, hypertension, type 2 diabetes mellitus, dyslipidemia, care level, and certification status).
IVg, Stage IV with gangrene; IVu, stage IV with ulceration; ref, reference; PAOD, peripheral arterial occlusive disease
Table 5. Univariate and multivariate analyses of minor amputations among inpatients treated for PAOD (2016–2018).
| Minor amputation | Univariate analysis |
Multivariate analysis
(Nagelkerke’s pseudo-R²: 0.414) |
||
| Odds ratio | p-value | Odds ratio | p-value | |
| PAOD stage − Fontaine IIb (ref) − Fontaine III − Fontaine IVu − Fontaine IVg |
1.00 7.79 [6.19; 9.81] 200.24 [165.61; 242.11] 1153.42 [954.75; 393.43] |
< 0.001 < 0.001 < 0.001 |
1.00 8.07 [6.41; 10.16] 206.44 [170.70; 249.67] 1149.46 [951.22; 1389.00] |
< 0.001 < 0.001 < 0.001 |
| Age (continuous) | 1.03 [1.03; 1.03] | < 0.001 | 1.00 [1.00; 1.00] | < 0.001 |
| Sex − male (ref) − female |
1.00 0.65 [0.63; 0.66] |
< 0.001 |
1.00 0.60 [0.59; 0.62] |
< 0.001 |
| Hypertension | 0.86 [0.85; 0.88] | < 0.001 | 1.05 [1.03; 1.08] | < 0.001 |
| Type 2 diabetes mellitus | 2.11 [2.07; 2.15] | < 0.001 | 1.34 [1.31; 1.37] | < 0.001 |
| Dyslipidemia | 0.68 [0.67; 0.69] | < 0.001 | 0.99 [0.96; 1.01] | 0.268 |
| Care level − Maximum care (≥ 800) (ref) − Central care (500–799) − Standard care (300–499) − Basic care (100–299) − Minimum care (< 100) |
1.00 1.01 [0.98; 1.04] 1.00 [0.97; 1.02] 0.93 [0.90; 0.96] 0.62 [0.56; 0.69] |
0.605 0.770 < 0.001 < 0.001 |
1.00 1.07 [1.04; 1.11] 1.08 [1.05; 1.11] 0.99 [0.96; 1.02] 0.69 [0.61; 0.77] |
< 0.001 < 0.001 0.560 < 0.001 |
| Certification status − Not certified (ref) − Certified |
1.00 0.96 [0.94; 0.98] |
< 0.001 |
1.00 1.04 [1.01; 1.06] |
0.004 |
The odds ratios are given with their 95% confidence intervals. In the multivariate analysis they were adjusted for all variables (PAOD stage, age, sex, hypertension, type 2 diabetes mellitus, dyslipidemia, care level, and certification status).
IVg, Stage IV with gangrene; IVu, stage IV with ulceration; ref, reference; PAOD, peripheral arterial occlusive disease
Acknowledgments
Acknowledgment
We thank Mr. Stefan Schiele, MSc of the Chair of Computer-Oriented Statistics and Data Analysis, University of Augsburg, for his advice on statistics during the compilation of the manuscript.
Footnotes
Conflict of interest statement
Prof. Kröncke has received lecture fees from Abbott Vascular.
The remaining authors declare that no conflict of interest exists.
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