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Acta Neurologica Belgica ISSN 0300-9009Volume 112Number 1 Acta Neurol Belg (2012) 112:19-25DOI 10.1007/s13760-012-0026-0

Prediction of hospitalization duration foracute stroke in Belgium

Veerle Beckers, Ann De Smedt, Robbert-Jan Van Hooff, Sylvie De Raedt, RitaVan Dyck, Koen Putman, Jacques DeKeyser & Raf Brouns

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ORIGINAL ARTICLE

Prediction of hospitalization duration for acute stroke in Belgium

Veerle Beckers • Ann De Smedt • Robbert-Jan Van Hooff •

Sylvie De Raedt • Rita Van Dyck • Koen Putman •

Jacques De Keyser • Raf Brouns

Received: 6 January 2012 / Accepted: 6 January 2012 / Published online: 10 February 2012

� Belgian Neurological Society 2012

Abstract We aim to predict the duration of hospitaliza-

tion for acute stroke in Belgium by evaluating the external

validity of the prolonged length of stay (PLOS) score and

by formulating a new prediction score that may be better

suited for the Belgian healthcare system. This single-center

retrospective study is based on data collected prospectively

from the departmental stroke registry. To validate the

PLOS score, receiver operating characteristic curves were

constructed and Hosmer–Lemeshow tests were imple-

mented. Odds ratios were calculated by models of logistic

regression, based on predictors of length of stay (LOS)

with significance in univariate analyses, and were trans-

lated into a new risk score. C-statistics for prediction of

LOS C7 days, LOS C14 days, and LOS C30 days using

the PLOS score were in the range of 0.6–0.7. Thrombolytic

therapy, mortality, and need for institutionalization had a

notable negative influence on the discrimination of the

PLOS score. Overall, the PLOS score performed better for

prediction of LOS C14 days than for LOS C7 days and

C30 days. The Belgian length of stay for stroke (BLOSS)

score is proposed as a simplified prediction model based

only on the NIHSS score and age. The PLOS score showed

moderate value for prediction of hospitalization duration

for acute stroke in this Belgian cohort. A prediction model

based only on age and stroke severity may be a worthy

alternative.

Keywords Stroke � Length of stay � Predictive score �Prognostic model � Validation � Epidemiology

Introduction

The duration of hospitalization for stroke is one of the

major cost-determining factors [1]. Reliable prediction of

the length of stay (LOS) is meaningful for the patient and

his family, and for professional caregivers as it would

facilitate planning of rehabilitation, daily management of

stroke units, and prediction of costs for hospitalization.

Previous reports agree on the predictive value of stroke

severity with regard to the duration of hospitalization, but

other determining factors differ greatly from study to study

[2–4]. This may be explained by relevant differences in

healthcare systems and local customs, and by heterogeneity

in the study populations (for instance exclusion of hem-

orrhagic stroke or thrombolytic therapy). Koton et al. [5]

derived the prolonged length of stay (PLOS) score from

NASIS, a prospective hospital-based national study in

Israel, for risk assessment of prolonged LOS (C7 days) for

acute hospitalization in stroke patients (Table 1). Temporal

validation was established by analyzing patient data of the

NASIS 2007 [5] and external validation of the PLOS score

V. Beckers

Department of Internal Medicine, Vrije Universiteit Brussel

(VUB), Universitair Ziekenhuis Brussel, Brussels, Belgium

A. De Smedt � R.-J. Van Hooff � S. De Raedt � R. Van Dyck �J. De Keyser � R. Brouns (&)

Department of Neurology, Center for Neurosciences (C4N),

Vrije Universiteit Brussel (VUB), Universitair Ziekenhuis

Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium

e-mail: Raf.Brouns@uzbrussel.be

K. Putman

Department of Medical Sociology and Health Sciences, Faculteit

Geneeskunde en Farmacie, Vrije Universiteit (VUB),

Brussels, Belgium

J. De Keyser

Department of Neurology, University Medical Center

Groningen, Groningen, The Netherlands

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DOI 10.1007/s13760-012-0026-0

Author's personal copy

was attempted on the 350 patients included in the first five

years (2002–2007) of the Oxford Vascular Study [6].

The aim of this study is to evaluate the predictive value

of the PLOS score for acute stroke hospitalization in the

Belgian healthcare system, which differs from the health-

care systems from which it was previously derived and

validated. In addition, this study aspires to formulate a

prediction score that may be better suited for the Belgian

healthcare system.

Methods

Patients and study design

This study has a single-center retrospective design and is

based on the analysis of data from the stroke registry from the

department of Neurology of the Universitair Ziekenhuis

Brussel. Digital data collection of the stroke registry is pro-

spectively obtained from consecutive stroke patients who are

admitted at the Stroke Unit. Only patients admitted between

January 2009 and December 2010, who were diagnosed with

acute ischemic stroke or intracerebral hemorrhage, were

included in the study. The diagnosis was confirmed by

cerebral imaging and senior neurologists with expertise in

stroke care. Patients with stroke mimics or transient ischemic

attacks (TIA, defined as a clinical presentation believed to be

secondary to focal cerebral ischemia but with symptoms

lasting less than 1 h and without proof of acute infarction on

structural neuroimaging [7]) were excluded from analysis, as

were those in whom onset of symptoms within 2 days prior to

admission could not be stated. Patients who were transferred

from another hospital or ward were not included unless

the onset of symptoms was less than 1 day. Execution of

this study was appraised by the Ethics Committee of the

Universitair Ziekenhuis Brussel.

Data collection

Both the stroke registry of the department and the medical

charts of the included patients were used for data collec-

tion. Patients were only included if the five variables to

calculate the PLOS score and data on the exact LOS were

available. Other data on the included patients were also

assembled: age, gender, blood pressure on admission,

medical history, prior medication use, Glasgow Coma

Score (GCS) [8], National Institutes of Health Stroke Scale

(NIHSS) score [9], premorbid modified Rankin Scale

(mRS) score [10], acute stroke treatment (i.e., thrombolytic

therapy), cerebrovascular risk factors (i.e., hypertension,

smoking, diabetes mellitus, personal or family history of

stroke or acute coronary syndrome, dyslipidemia, obesity,

peripheral artery disease), stroke etiology (TOAST classi-

fication) [11], residence before the stroke, mortality, and

need for institutionalization at discharge.

The LOS was calculated from admission at the emer-

gency room or from symptom onset if the patient was

already hospitalized at another hospital ward until dis-

charge from the department of Neurology. Hospitalization

days on another ward for stroke-related complications also

contributed to the calculation of LOS.

Statistical analyses

As the PLOS scores and LOS were not normally distributed

(Kolmogorov–Smirnov test), results are presented as

median (interquartile range, IQR), and non-parametric tests

(Mann–Whitney test and the Spearman’s rank correlation

coefficient) were applied. The validity in discrimination of

the PLOS score for prediction of LOS C7 days, LOS

C14 days, and LOS C30 days was assessed by construct-

ing receiver operating characteristic (ROC) curves and

c-statistics (95% confidence intervals, CI). Calibration of

the PLOS score, to observe a possible significant difference

between the observed and predicted rates by the PLOS

score, was evaluated by the Hosmer–Lemeshow goodness-

of-fit test.

In order to derive a modified prediction score better

suited for Belgian stroke patients (Belgian length of stay

for stroke, BLOSS), we performed univariate testing to

identify associations between LOS and variables that in

general are available shortly after admission (age, gender,

Table 1 The five predictors of the PLOS score [5, 6]

Predictors Points

Type of stroke

Ischemic stroke 0

Hemorrhagic 1

Decreased level of consciousness at admission

Absence 0

Presence 1

History of congestive heart failure

Absence 0

Presence 1

History of atrial fibrillation

Absence 0

Presence 1

NIHSS at admission

0–5 0

5–10 2

11–20 3

[20 1

NIHSS National Institutes of Health Stroke Scale

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premorbid mRS, admission NIHSS, admission systolic

blood pressure, admission diastolic blood pressure,

decreased consciousness, stroke subtype, stroke etiology,

and cerebrovascular risk factors (hypertension, diabetes

mellitus, dyslipidemia, smoking, obesity, atrial fibrillation,

coronary artery disease, heart failure, peripheral artery

disease, previous stroke or TIA, family history of stroke or

TIA)), followed by logistic regression analysis using a

backward stepwise method (entry criteria: 0.05 and

removal criteria: 0.10) on variables proven significant after

univariate analysis. The resulting beta coefficients were

converted into odds ratios (OR). For conforming to the

method of derivation of the PLOS score [5], we translated

the increase in OR of the different categories of the vari-

ables into specific risk scores.

The van Elteren Cochran–Mantel–Hanszel (CMH) test

assessed differences in the distribution of the PLOS and

BLOSS scores of patients with longer and shorter duration

of hospitalization [12].

Statistical computations were performed with the SPSS

software package version 17.0 (SPSS Inc, Chicago, Ill),

except for evaluation of the CMH test which was carried

out in SAS version 9 using the PROC FREQ function.

Statistical significance was defined as a P-value \0.05.

Results

Study population

A total number of 367 stroke patients hospitalized for acute

ischemic stroke (88.3%) or intracerebral hemorrhage

(11.7%) was included in the study (Fig. 1). 46.9% of

patients were male and the mean (standard deviation, SD)

age was 73.9 (13.2) years. The prevalence of arterial

hypertension, diabetes mellitus, dyslipidemia, previous

stroke or TIA and smoking was 69.8, 21.3, 42.0, 22.6, and

14.5%, respectively. The median (IQR) NIHSS score at

admission was 5 (2–14). Thrombolytic therapy was applied

in 18.2% of patients with ischemic stroke. Thirty-seven

patients (10.1%) died during initial hospitalization and 121

patients (33%) had a need for institutionalization upon

discharge. The median LOS was 9 days (IQR 5–14 days).

PLOS score

Table 2 summarizes the number of patients and median LOS

in function of the PLOS score. ROC curves were constructed

for prediction of LOS C7 days, LOS C14 days and LOS

C30 days (Fig. 2). The c-statistic for LOS C 14 days fea-

tured the highest area under the curve (0.66, 95% CI

0.60–0.72). The Hosmer–Lemeshow goodness-of-fit test

showed no significant difference between observed and

predicted rates. Shift analysis by the CMH test objectified a

significant shift towards higher PLOS scores in patients with

LOS C7 days (P \ 0.001), C14 days (P \ 0.001), and

C 30 days (P = 0.039) in comparison with patients with

no prolonged hospitalization (LOS\7 days,\14 days, and

\30 days, respectively) (Fig. 3a).

BLOSS score

Univariate analysis identified significant associations

between the LOS and age (P \ 0.001), admission NIHSS

Stroke patients enrolled in the registry of the stroke unit

TIA's and stroke mimics excluded

N = 429

Acute stroke

Symptoms onset < 1 day

Subacute stroke

Symptoms onset > 1 day

No transfer other hospital

with symptoms onset > 1 day

Transfer other hospital

with symptoms onset > 1 day

Data collected sufficient Data collected not sufficient

Total analyzed population Excluded patients

Fig. 1 Flow diagram of the study population

Table 2 Number of patients and length of stay in function of the

PLOS score

PLOS score n (%) Median LOS (IQR)

0 134 (36.5) 7 (5–10)

1 39 (10.6) 7 (5–11)

2 58 (15.8) 10 (6–15)

3 71 (19.4) 11 (7–15)

4 35 (9.5) 11 (5–17)

5 28 (7.6) 12 (6–21)

6 2 (0.5) 16 (15–16)

IQR interquartile range, LOS length of stay, PLOS prolonged length

of stay

Acta Neurol Belg (2012) 112:19–25 21

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score (P \ 0.001), female gender (P = 0.011), and

decreased consciousness (P = 0.036). Multivariate regres-

sion analysis retained only age (P = 0.005) and NIHSS score

(P \ 0.001) at admission as independent predictors of

LOS C 14 days. Table 3 summarizes the OR, converted

from the beta coefficients of the logistic regression analysis.

Calculations showed a significantly increased risk estimation

for LOS C 14 with increasing age towards 85 years and

NIHSS score up to 20. Patients older than 85 and NIHSS score

higher than 20 showed a reduced risk estimation for pro-

longed hospitalization. For conforming to the derivation

method of the PLOS score [5], the OR of the different cate-

gories was translated into specific risk scores. This resulted in

the novel clinical prediction model for prolonged LOS

C14 days (BLOSS score, Table 3).

Figure 4 shows the proportional increase of patients

with prolonged LOS C14 days by increasing BLOSS and

PLOS. The c-statistic of the BLOSS score for prediction of

LOS C14 days is higher (0.70, CI 0.64–0.76) than for the

PLOS score, and the BLOSS score is well calibrated in

our population (Hosmer–Lemeshow goodness-of-fit test;

P = 0.371). The CMH test demonstrates a significant shift

in the spectra of the BLOSS score towards higher BLOSS

scores in the cohort of patients with prolonged hospital-

ization (LOS C14 days; P = 0.001) (Fig. 3b).

Subpopulations

Additional analyses were performed in patients surviving

the initial hospitalization (n = 330; 89.4%), in patients

receiving thrombolytic therapy, and in patients requiring

institutionalization (discharged to rehabilitation center or

nursing facility, n = 121; 33.0%). C-statistics for predic-

tion of LOS for hospital survivors were moderately better

than in the total study population (PLOS and BLOSS for

LOS C14 days; 0.68 and 0.71, respectively). Prediction of

LOS C14 days in patients treated with thrombolytics

appeared to be unreliable for PLOS but not for BLOSS

(c-statistics 0.49 and 0.73, respectively). Length of stay

could not be adequately predicted by PLOS or LOS in

those requiring institutionalization (c-statistics 0.52 and

0.56, respectively).

Discussion

To be clinically useful, predictors of LOS should be

available shortly after admission. Several studies have

looked into the potential predictive value of demographical

and clinical parameters for LOS, both in acute hospital-

ization (stroke unit) and total hospitalization (stroke unit

and rehabilitation). In the Copenhagen Stroke Study [13], a

relation between stroke severity and increased LOS for

total duration of hospitalization was identified. A similar

relation was identified for single marital status, but age,

gender, comorbidity, smoking and stroke type (hemorrhage

or ischemic stroke) were not retained as independent pre-

dictors. Stroke severity was also found to be the strongest

predictor for LOS for acute hospitalization in 330 Tai-

wanese patients with first-ever ischemic stroke [3]. Simi-

larly, Appelros et al. [4] found stroke severity assessed by

the NIHSS to be a strong predictor of LOS, both for acute

hospitalization and total stay in a single-center cohort of

first-ever stroke patients in Sweden. Other independent

factors that determined a prolonged acute LOS in this study

were smoking, pre-stroke dementia and non-lacunar stroke.

Our study cohort is a representative sample of the Bel-

gian acute stroke population with analogous demographic

and stroke characteristics [14]. In general, daily stroke care

in Belgium is organized concordant to international stan-

dards and the consensus document prepared by the Belgian

Stroke Council [15]. However, relevant differences

between the Belgian health care system and other health-

care systems exist. For instance, stroke rehabilitation is

usually organized in specialized wards or institutions rather

than at the neurology ward or the stroke unit. This implies

waiting lists due to interdepartmental patient transfers, a

known hitch in the Belgian healthcare system. This is the

major reason for the rather long LOS for acute stroke

hospitalization in our population. Prediction of LOS

C14 days therefore may be more clinically relevant for

Belgian stroke patients than LOS C7 days (the Israeli

alternative) [5] or LOS C30 days (the UK alternative) [6].

Fig. 2 Receiver operating characteristic curves of the PLOS score for

prediction LOS C7 days, LOS C14 days and LOS C30 days

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In accordance with previous studies on the predictive

value of the PLOS score [5, 6], we found moderate pre-

dictive value in our cohort of Belgian stroke patients, with

c-statistics in the range of 0.60–0.70. Prediction of LOS

C14 days scored better than prediction of LOS C7 days

and LOS C30 days. The limited predictive value of the

PLOS and the BLOSS models in patients requiring insti-

tutionalization can be explained by the waiting lists for

rehabilitation or nursing facilities. Similarly, the models

may have little clinical use in patients treated with

thrombolytics or in those not surviving the acute phase of

stroke. The confounding role of mortality during the hos-

pitalization was already established OXVASC population

[6] and can be attributed to the fact that mortality shortens

the LOS in patients who otherwise would have been hos-

pitalized longer. The low discrimination in those receiving

Fig. 3 Shift analysis LOS

\14 days versus LOS C14 days

of the PLOS score (a) and the

BLOSS score (b)

Table 3 Odds ratios of predictors for prolonged LOS [14 days and

derivation of the points attributed in the BLOSS score

Predictor Categories OR (95% CI) Points attributed

for BLOSS score

Age (years) B65 1 (Ref.) 0

66–75 1.70 (0.72–4.00) 1

76–85 3.25 (1.52–6.93) 3

C85 2.06 (0.88–4.81) 2

NIHSS score B5 1 (Ref.) 0

6–10 2.04 (1.00–4.17) 1

11–20 4.64 (2.44–8.81) 3

[20 3.34 (1.61–6.95) 2

BLOSS Belgian length of stay for stroke, CI confidence interval,

NIHSS National Institutes of Health Stroke Scale, OR, odds ratio, Ref.reference

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thrombolytic therapy can logically be accounted to the

interventional nature of thrombolytic therapy. The value of

the BLOSS score in this subpopulation warrants further

study in a larger study population.

Although a moderate statistic validity was observed for

the PLOS score in our population, with results bordering on

the same range as those of the NASIS and OXVASC

studies [5, 6], the clinical validity of this predictive model

may still be questioned as an area under the curve above

0.70 is desired for use in clinical circumstances.

A first evaluation of the BLOSS score in the original

derivation population showed slightly better c-statistics

than the PLOS score, good calibration and a significant

shift in the BLOSS spectra towards higher scores in pro-

longed LOS, which suggest the BLOSS score as a simple

yet worthy alternative for prediction of LOS C14 days in

Belgian acute stroke patients. In clinical practice, reliable

prediction of prolonged hospitalization is meaningful, not

only for the patient and his family but also for the medical

staff and the social services. It facilitates planning of

rehabilitation, daily management of stroke units and pre-

diction of costs for hospitalization.

Some limitations of the present study should be taken

into account. First, the retrospective, single-center design

limits extrapolation to other stroke centers. Second, the

study cohort counted 367 acute stroke patients, which is

considerately less than the derivation cohort of the PLOS

score [5] but similar to recent studies on hospitalization

duration in stroke [3, 4, 6]. Moreover, the number of events

per variable was 92, indicating an adequate sample size for

logistic regression analysis [16]. Although the Hosmer–

Lemeshow goodness-of-fit test indicated a good calibration

of the scores in every aforementioned subpopulation, it

cannot be excluded that sample sizes were too small causing

too weak power of the test to exclude lack-of-fit [17].

Our study is of interest because we confirm the validity

of the PLOS score in Belgian stroke patients. Using the

score for prediction of LOS C14 days is preferable in the

Belgian healthcare system. However, the confounding

effect of mortality, thrombolytic therapy and institutional-

ization limits its practical use. We propose a new predic-

tion model, the BLOSS score, as a simple alternative.

Clinical and statistical validation of the BLOSS score will

be sought by prospective multi-center study.

Conflicts of interest None.

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Fig. 4 Percentage of patients

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the PLOS and the BLOSS score

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