Cost methods
A number of methods have
been employed by researchers looking to measure costs in intensive care. The
choice of method is however, dependent on the purpose of the study [9]. As an example, the aim of a cost-effectiveness
analysis of two alternative therapies would be to measure actual cost
differences between patients, dependent on their choice of therapy. It would
thus be important to use a ‘bottom-up’ method to ascribe resources to the
individual patients.
Costing methods differ both
in their approach and in their inclusion of different cost components. Costs
can be defined both in economic and accountancy terms, and categorised into
‘direct’ and ‘indirect’ costs. Direct costs are those ascribed to patients and
would include drugs and fluids. Examples of indirect costs are management,
utilities and capital equipment and tend to be those not easily ascribed to
individual patients. It is often the case that indirect costs are excluded from
studies, as they have little influence on marginal costs (the cost of treating
an additional patient). A lack of consensus also exists as to how these
indirect costs should be calculated.
History of Costing: Studies before 1995
Before 1995 very few studies
of intensive care cost had been undertaken. A review of twenty studies (that
included a defined costing method) was undertaken in 1995 [9]. Of the twenty studies, fifteen used a ‘bottom-up’
costing approach and the remaining five, a ‘top-down’ approach.
Bottom-up or micro-costing
necessitates the accurate measurement of resources at a unit level, for example
the delivering an analgesic would be costed by measuring the numbers of
syringes used, the analgesic itself and the amount of nursing time required to
prepare and deliver the drug. Against these values, unit costs are then
assigned. The cost of nursing staff, for example, would be calculated using the
cost per minute of the nurse and the amount of time spent.
Top-down costing uses the
total annual costs of the ICU to determine an average cost per patient and per
patient day. It assumes that all patients consume similar amounts of resources
on a daily basis. Studies often employ a combination of bottom-up and top-down
costing calculations because it is quite difficult to measure nursing and
medical time spent with patients.
More than half of the
studies reviewed by Gyldmark (n=13) collected data retrospectively, whilst the
remaining nine collected prospective data. Perhaps the most surprising
observation was the variation in cost components measured in the studies
reviewed. Seven of the twenty studies measured the cost of medical and nursing
staff time. Given that staff costs account for approximately fifty three
percent of total costs [5] it is surprising that thirteen studies excluded
these. Eight of the twenty studies incorporated the cost of disposables and
nine studies took into consideration the cost of drugs and fluids. Hospital
charges were used instead of costs in thirteen of the studies. The cost per
patient reported in these studies ranged from $1,783 to $48,435. Although the
costs varied considerably, valid comparisons between the research findings were
hampered because of the different methods used in each of the studies. An
additional review of costing methodologies also identified the extent of
variation in the methods of cost apportionment [10]. Both reviewers recommended a standard method for the
measurement of intensive care costs.
A number of studies of
intensive care cost quote mean total costs per patient [11-14] [15]. The total costs determined in these studies range
between £2,310 - £6,142 and $1,156 - $30,136. Although the total cost per
patient varies considerably between these studies, the comparisons are limited
in that total cost is influenced by length of stay.
Methodological developments since 1995
Since 1995, a number of
studies measuring the costs of intensive care have emerged in the literature.
A method for comparative
costing of individual intensive care units has been developed in the UK [5]. This costing methodology uses a ‘top down’ approach
to determine average costs per patient, per patient day and per ICU bed to
perform inter-ICU cost comparisons. The cost data is collected from different
ICUs according to precise definitions. Using this method, it is possible to
measure costs for medical and nursing staff, consumables (drugs and fluids,
disposable equipment, nutritional products, blood and blood products) and
clinical support services (radiology, laboratory services, physiotherapy and
specialised bed therapy). A study of twenty-one UK ICUs using this method
determined a median (IQR) cost per patient day of £904 (£828 - £1,163) [16]. The study explored possible reasons for the
variation in costs observed between the individual ICUs by undertaking a
regression analysis. The results showed that ninety-three percent of the
variation in expenditure on disposable equipment was explained by the number of
ICU beds, the number of admissions, and the presence of a high dependency unit
(HDU).
The top-down approach is a
simple approach to costing that can be easily applied in any ICU, however it
does not determine individual patient costs. Costs are calculated from the
hospital perspective, rather than at the patient level and hence the method is
limited in the evaluation of alternative treatments and interventions.
An activity-based method was
used to accurately measure the costs of individual patients developed in 1995 [17]. Activity based costing is a form of bottom-up costing,
where the resource use for each individual patient is determined according to
the activities of care delivered to that patient. An activity of care is
defined as ‘any patient-related task requiring the use of ICU resources’ [1]. Over four hundred activities of care were configured
within this study and included all drugs, treatments, major monitoring
procedures used on the ICU and background nursing care. Total patient related
costs of care for each individual patient were derived by summating the cost of
each activity of care delivered to that patient. This method determined n mean
(SD) patient related cost for the first twenty-four hours of care in the ICU of
£753.50 (£328). When non-patient related
costs were incorporated, an average cost per patient day was estimated at
£1,152.
A study of the cost per ICU
day of medical and surgical patients compared to non-ICU days was undertaken in
1995, using a bottom-up costing method [18]. Costs were determined using a Patient Resource
Consumption Profile (PRCP), a database containing patient specific costs on a
daily basis. By manually tracing and recording the elements of care delivered
to each patient it was possible to assign PRCP costs to individual patients.
This study determined a median cost per ICU day (cost per non-ICU day) for
medical survivors of $1,357 ($232) and a median cost per ICU day for
non-survivors (cost per non-ICU day) of $1,502 ($250). The median cost per ICU
day (cost per non-ICU day) for surgical survivors was $1,501 ($281) and for
surgical non-survivors, $1,463 ($325). The study showed that a one-day
substitution of general ward care for ICU care would result in a cost reduction
of $1,200.
Although the bottom-up
approach facilitates economic evaluations of ICU resources, the process is
laborious and expensive [6]. The necessary data can be collected manually for
each patient, although this is only feasible for short periods of time. An
alternative option is to automate the collection of data, however, the
development and implementation of computerised systems capable of determining
individual patient costs, is extremely complex and costly.
Costing of disease processes
Bottom-up costing has also
been used to determine the costs associated with specific disease processes [19]. A study of the patient-related costs of care for
sepsis patients showed patients with severe sepsis or early septic shock to be
significantly more expensive to treat than non-sepsis ICU patients. Data was
analysed according to the day upon which sepsis was diagnosed. Patients septic
on admission (group one) to the ICU had a median (interquartile range) total
cost per patient of $3,802 ($1,865 - $11,676), patients who became septic on
day two in the ICU (group two) had a median (interquartile range) total cost of
$13,089 ($5,793 - $22,235) and for patients septic after their second day in
the ICU (group three), the median total cost per patient was $17,963 ($13,031 -
$28,547). The median total cost per patient of non-sepsis patients (group four)
was $1,667 ($980 - $2,772). When median total costs per patient for survivors
and non-survivors were compared, survivors were more expensive in groups one
and three and four although non-survivors were more expensive in group two. The
median length of stay of survivors was higher than non-survivors in each group
although the difference in length of stay between survivors and non-survivors
in group two was smaller than the other groups.
An investigation of the cost
of critically ill cancer patients was undertaken as part of a
cost-effectiveness analysis. Charges were used as a measure of cost for each
patient entering the study. The use of charges as a surrogate for cost have
been criticised in that they do not represent actual hospital costs, and
therefore it is uncertain what the charge actually represents [9, 10]. The study determined a cost per life year gained for
patients with solid tumours of $82,845, and the cost per life year gained for
patients with haematological cancers to be $189,339. The study suggested that
the cost per life year gained for patients with solid tumours and patients with
haematological cancers is greater than that for other medical scenarios.
Further thought should be directed towards the decision to withdraw treatment
in cases where the chance of survival is small.
The need for an accurate cost proxy
In order to make decisions
regarding the allocation of resources in the ICU, we must be capable of
assigning costs to individual patients. Although the bottom-up method allows
such costs to be determined, the implementation of such a method is not
feasible in every ICU, due to time and resource constraints. For this reason,
it is necessary to determine an accurate cost proxy. Examples of potential
proxies include the Acute Physiology and Chronic Health Evaluation (APACHE)
score [20], the Therapeutic Intervention Scoring System (TISS) [21], the (NEMS) and ICU length of stay.
A significant correlation
between APACHE II scores and cost on the first day of a patients’ stay
(P<0.0002) have been reported [22]. However, a different study, calculating APACHE II
scores daily found a poor relationship between APACHE II and daily cost [23].
There have been a number of
research studies investigating the relationship between TISS and cost [15, 24-26]. The original TISS study [21] calculated individual patient costs for ten ICU
patients over a twenty-four hour period using the bottom up approach, and
correlated TISS and cost to determine a cost per TISS point of $10. However,
when determining individual patient costs, salaried costs - the most
significant proportion of the ICU budget [5] were evenly distributed between the patients. This
perhaps explains why a good relationship was observed between TISS and cost in
this study. TISS, originally described as a method for quantifying therapeutic
interventions, has been adapted in individual ICUs to reflect local practice.
As a consequence of this, the results of existing studies of the relationship
between TISS and cost are not comparable. One study estimated the total annual
expenditure of an ICU and divided it by the total number of TISS points to
determine a cost per TISS point of $16 [24]. However this study
assumed that the cost of resources used for every TISS point are the same.
There have been studies in which a poor relationship between TISS and cost has
been observed [23, 26]. In both these studies, when individual daily patient
costs were correlated against TISS, a poor relationship was observed (r²=0.26, P<0.001) [26], (r²=0.26, P<0.001) [23].
Further investigation is
necessary into the relationship between cost and cost proxies in order to
devise a simple yet accurate method for the determination of individual patient
costs.
The future
It is apparent that there is
no standard method in place for the determination of individual patient costs
within the ICU. Without accurate cost data, the value of economic evaluations
is limited. If we are unable to make appropriate decisions regarding the
allocation of resources, due to a lack of reliable information, the likelihood
of resource waste is high. A standard method for measuring the cost of
individual intensive care patients would be beneficial for use alongside
clinical trials. In such circumstances, sufficient data would be obtained to
perform economic evaluations such as cost-effectiveness and cost-minimisation
studies. Detailed patient level costing also has the potential for the
development of Healthcare Resource Groups (HRGs) for ICU patients.
The linkage of costs to
outcome measures would enable further investigation into the costs associated
with patients who do not survive their ICU admission. This has the potential
for identifying areas in which resources can be saved. In order to do this, the
evaluation of scoring systems for the prediction of mortality is necessary.
Five years ago, it was
identified that no standard method for determining the cost of intensive care
was in place [9] [10]. Since 1995, a standard method for determining total ICU costs has been implemented in
the UK. We advocate the development of a method for costing at individual
patient level that is standard, simple and accurate
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