Patient Classification Systems

ABSTRACT

INTRODUCTION: The development of patient classification systems (PCS) in fields other than acute medicine raises the
question if the principle of using existing data (i.e. diagnoses; procedures where available) is sufficent to describe the
products of hospital care.

METHODS/MATERIAL: The essence of a PCS (type "iso-cost") is to estimate costs of treatment needed in a defined
setting by means of a description of the patient status (conditions) and the treatment goals. Two hypotheses guided our
research into PCS development: (1) The description of patient status and treatment goals has to include multiple aspects
which ideally are coded by using scales to show changes during the course of time. (2) In a multiprofessional team,
costs of treatment of each professional sector can depend on different aspects of the patient status. Therefore, in a first
step treatment costs could be described multidimensionally: for each profession sector separately. - In a test study, 1795
treatment weeks of 274 patients of 4 medical rehabilitation institutions were described by a variety of patient status
indicators.

RESULT: The test study showed that the sum of nursing times per week and patient were best grouped by a
two-dimensional grid constructed by using the motor scale and the cognitive scale of the Functional Independence
Measure (FIM). These scales are used as indicators of the patient status. The six final groups lead to a variance
reduction of approx. 65%. But the time spent by several therapeutic professionals could not be explained by the same
indicators.

CONCLUSIONS: The test study encourages further research about the introduction of multidimensional and scaled
measures in order to explain the multidimensional cost vectors of a multiprofessional health treatment. In the acute
setting a first model could be to use DRGs to estimate costs related to or dependent on physicians\' activities and a
measure of functional status to estimate (independent) nursing costs. A proposed research field is the treatment of
patients with chronic diseases.

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INTRODUCTION

The development of patient classification systems (PCS is normally restricted by the obligation to use existing data. The results are interesting.
But if we look at them with the eyes of a statistician we must say they are not very convincing. As indicator for the goodness of the grouping
result, the reduction of variance of costs or length of stay is often used. The most detailed one-dimensional PCS for acute stays is probably the
APR-DRG system. 3M - the owner of APR-DRG - has published an overall reduction of variance of 53% on american data for untrimmed
charges (see table below). This is a higher value than other systems can present; but from the statistical viewpoint this value is still clearly
below the limit of 75% for good values.

Table 1: Variance reduction (R2) of several DRG systems [1]

 
Untrimmed length of stays
Untrimmed charges (bill amounts)
All
Medical
Surgical
All
Medical
Surgical
HCFA-DRG
31%
29%
33%
41%
25%
41%
SR-DRG
34%
30%
38%
44%
27%
45%
RDRG
37%
35%
38%
46%
35%
46%
AP-DRG
37%
36%
37%
47%
37%
45%
APR-DRG
42%
38%
45%
53%
42%
52%



 
Still today we have lower values for medical groups compared to surgical groups, particularly if we look at the results for charges. That shows
that diagnoses are a weaker grouping criterion than procedures. Knowing that PCS should derive groups which are classified relating to the
ressources needed, an ideal PCS would use patient status (conditions) and preferably also treatment goals as grouping criteria, but not
treatment characteristics. Diagnoses meet this demand; procedures - which produce better results - do not.

These observations and the development of PCSs in fields other than acute medicine, where fewer data is available, raise the questions:

Besides the diagnoses and procedures of physicians, should other criteria be used to define patient groups? From which professional
sectors would we have to use additional data?
 
Do we have to change the idea that we can define the products of hospitals or of other treatment institutions by using a
one-dimensional product list?

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METHODS

Hypotheses

The essence of a PCS (type "iso-cost") is to estimate costs of needed treatment in a defined setting by a description of the patient status
(condition) and the treatment goals. Two hypotheses guided our research into PCS development: (1) The description of patient status and
treatment goals