Figure 1 provides a graphic illustration of grouping algorithms and classification variables of PCS in 11 European countries. The figure includes classification variables of those DRGs that together account for more than 97% of appendectomy cases in each country. On the left hand side, the figure specifies for each country the version of the PCS and the percentage of all appendectomy cases shown in the graph. The arrows indicate the sequence in which different types of classification variables are considered in the grouping algorithm. In addition, indicators to assess the composition of DRGs and the relative resource intensity of cases within each DRG are shown. Finland and Sweden are shown together with only one grouping algorithm as both use the NordDRG system which is identical for the presented DRGs.
Patient classification of appendectomy cases in Europe
Overview: number of DRGs and number of classification variables
The figure demonstrates that there is great variation in DRG systems across Europe. The number of DRGs comprising more than 97% of cases differs considerably in different countries’ systems. In Ireland, appendectomy cases are classified into only two DRGs, while in Germany 11 DRGs exist to account among other things for different levels of complexity and different age groups.
In addition, the number of classification variables differs: the Austrian system differentiates only between different age groups, when classifying appendectomy patients; the French system differentiates (1) primary diagnoses, (2) level of complications or comorbidities (CC), (3) age groups, (4) with or without death during admission, and (5) length of stay.
Characteristics of classification variables
Different DRG systems classify appendectomy patients on the basis of different classification variables. There are three main groups of classification variables: (1) treatment characteristics, (2) patient characteristics, and (3) provider/setting characteristics. Only the first two are considered in most DRG systems.
In all systems, treatment characteristics, i.e., the procedure of appendectomy dominates the grouping algorithm and is always considered prior to the specific primary diagnosis except in the Dutch Diagnose Behandeling Combinaties (DBC) system. Only the All-Patient (AP)-DRG system in use in Spain and the Dutch DBC system differentiate between laparoscopic and open appendectomy. In the German (G)-DRG system and the AP-DRG system, a small number of patients is classified on the basis of other small intestinal/digestive system surgical procedures. The length of stay (LOS) is considered only in the French system.
A maximum of four patient characteristics are considered in the grouping process. In seven countries, the DRG systems differentiate between patients with a primary diagnosis for complicated appendicitis (i.e., appendicitis with generalized peritonitis or peritoneal abscess, each defined by specific ICD-10 codes), and those without. In most countries, the presence of relevant secondary diagnoses, i.e., complications and CC, also influences the classification of patients. However, while some countries’ systems only differentiate between with and without CC, others define several levels of CC (e.g., major CC in the AP-DRG system or level one to four CC in the French system), and again other systems calculate cumulative patient clinical complexity levels. Furthermore, age plays an important role in the classification process of several systems (i.e., Austria, England, France, and Germany). Interestingly, the French system differentiates between elderly (i.e., above 80 years) and others, whereas the German system differentiates between children (i.e., below 10 or below 15 years) and others. Death is considered a classification variable only in the French Groupes Homogènes de Malades (GHM) system.
Provider and setting characteristics are considered only in the Finnish and Swedish versions of NordDRGs and in the Dutch DBC system. In these systems, the grouping process differentiates between cases treated in inpatient and outpatient settings (not shown in the case of the Netherlands, where only very few cases are concerned). In addition, the Dutch DBC system considers provider characteristics by determining the department, where patients are treated (i.e., surgery).
Composition of DRGs and variation in relative resource intensity
In most countries, the vast majority of appendectomy EoC cases are grouped into the shadowed DRG (in Fig. 1) containing the index case (see Table 1), i.e., between 55% in Germany and 92% in Ireland. Finland is the only country, where 56% of patients are classified into a DRG containing appendectomy cases with generalized peritonitis or peritoneal abscess or patients with other complications and comorbidities. Within these index DRGs, almost all patients conform to our EoC definition (i.e., around 90% or above—shown in the second to last column). Only in Austria, the index DRG includes about 25% of patients that do not have a diagnosis of appendicitis. This might be explained by the fact that the diagnosis is not part of the Austrian grouping algorithm.
The cost index shows that the index DRG is the lowest-valued DRG in all countries except in Finland and Sweden, where separate “outpatient” DRG cost weights exist that are about 20% lower than the index DRG in Finland and 55% lower than the index DRG in Sweden. In general, in DRG systems with only two or three DRGs for appendectomy patients (i.e., in Austria, England, Finland, Sweden, Ireland, the Netherlands, and Poland), even the highest-valued DRG has a cost index below 2, implying that the systems do not adequately account for cases that are more than twice as complex as the index case. In Spain (Catalonia, AP-DRG V23), the most complex DRG containing more than 3% of patients and accounting for major complications such as chronic heart failure or pneumonia has a cost index of 4.75. In France, the most complex DRG (patients with complicated appendicitis, level 4 CC or level 3 CC and age greater than 80 years, and a LOS longer than 5 days) is valued more than five times as high as the index case.
In DRG systems where age is considered in the classification process, hospitals generally receive higher payments for elderly patients and for children. The differences can be quite large: For example, in Austria patients above age 69 have a cost index of more than 1.6. However, the difference between children and adults is relatively small in England and Germany. In the AP-DRG system and the Dutch DBC system, the only two systems that differentiate between open and laparoscopic appendectomy, hospitals receive higher payments for laparoscopic appendectomy than for open appendectomy. The difference between open and laparoscopic appendectomy is relatively small in Spain but amounts to 17% in the Netherlands.
In countries differentiating between complicated and uncomplicated appendicitis as primary diagnosis, the cost index is considerably higher for complicated appendicitis. In all countries except for Finland, the cost index is at least 1.4 for complicated appendicitis cases. Only in Finland, where almost all patients are classified as complicated appendicitis, the cost index is around 1.1.
DRGs and hospital quasi prices for case vignettes
Table 4 shows a comparison of DRGs and hospital quasi prices reflecting national average hospital payments for each case vignette under the assumption that hospital payment would be exclusively based on DRGs. For each case vignette, the first column specifies the DRG into which a case vignette patient would be classified and whether he would be considered an inlier or an outlier, i.e., whether the predefined length of stay is below or above the DRG system-specific lower or upper length of stay threshold. The second column specifies for each patient the corresponding quasi price. In the last column of the table, the index DRGs (see Fig. 1) and corresponding quasi prices are presented.
Apparently, large variation in hospital payments exists across countries. In general, costs appear to be lower in countries with a low GDP per capital , i.e., Estonia and Poland, and high in countries with a higher GDP (even though exceptions exist). Interestingly, however, countries that pay a higher price for one patient do not necessarily pay a higher price for all kinds of patients. For example, hospitals in France would receive much higher payments for appendectomy performed on a young patient, with peritoneal abscess, wound infection disruption of the operation wound and a long length of stay (patient 3) than hospitals in England. However, hospitals in England would receive higher payments for performing appendectomy on a young patient with no secondary diagnoses and a short length of stay (patient 4) than hospitals in France.