Poor performance of the modified early warning score for predicting mortality in critically ill patients presenting to an emergency department

doi:10.5847/wjem.j.issn.1920-8642.2013.04.005

Abstract

Abstract:

BACKGROUND: This study was undertaken to validate the use of the modified early warning score (MEWS) as a predictor of patient mortality and intensive care unit (ICU)/ high dependency (HD) admission in an Asian population.
METHODS: The MEWS was applied to a retrospective cohort of 1 024 critically ill patients presenting to a large Asian tertiary emergency department (ED) between November 2006 and December 2007. Individual MEWS was calculated based on vital signs parameters on arrival at ED. Outcomes of mortality and ICU/HD admission were obtained from hospital records. The ability of the composite MEWS and its individual components to predict mortality within 30 days from ED visit was assessed. Sensitivity, specificity, positive and negative predictive values were derived and compared with values from other cohorts. A MEWS of ≥4 was chosen as the cut-off value for poor prognosis based on previous studies.
RESULTS: A total of 311 (30.4%) critically ill patients were presented with a MEWS ≥4. Their mean age was 61.4 years (SD 18.1) with a male to female ratio of 1.10. Of the 311 patients, 53 (17%) died within 30 days, 64 (20.6%) were admitted to ICU and 86 (27.7%) were admitted to HD. The area under the receiver operating characteristic curve was 0.71 with a sensitivity of 53.0% and a specificity of 72.1% in addition to a positive predictive value (PPV) of 17.0% and a negative predictive value (NPV) of 93.4% (MEWS cut-off of ≥4) for predicting mortality.
CONCLUSION: The composite MEWS did not perform well in predicting poor patient outcomes for critically ill patients presenting to an ED.

Key words: Modified early warning score, Emergency department, Outcomes, Triage

Le Onn Ho, Huihua Li, Nur Shahidah, Zhi Xiong Koh, Papia Sultana, Marcus Eng Hock Ong. Poor performance of the modified early warning score for predicting mortality in critically ill patients presenting to an emergency department[J]. World Journal of Emergency Medicine, 2013, 4(4): 273-278.

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References 10

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Variables	MEWS <4 (n=713)	MEWS ≥4 (n=311)	Pvalue
Age, mean (SD)	62.3 (15.4)	61.4 (18.1)	0.44
Gender, ratio (M:F)	1.80	1.10	<0.001
Race (%)
Chinese	468 (65.6)	221 (71.1)	0.39
Malay	111 (15.6)	42 (13.5)
Indian	92 (12.9)	34 (10.9)
Others	42 (5.9)	14 (4.5)
Co-morbidities (%)
Nil	60 (8.4)	22 (7.1)	0.47
Hypertension	404 (56.7)	154 (49.5)	0.03
Diabetes	240 (33.7)	98 (31.5)	0.50
Heart disease	264 (37.0)	98 (31.5)	0.09
Cancer	48 (6.7)	31 (10.0)	0.07
Stroke	48 (6.7)	24 (7.7)	0.57
Respiratory disease	74 (10.4)	49 (15.8)	0.01
Renal disease	99 (13.9)	39 (12.5)	0.56

Variables	MEWS <4	MEWS≥4	Pvalue
Outcomes (%)
Died	47 (6.6)	53 (17.0)	<0.001
Admitted to ICU	137 (19.2)	64 (20.6)	0.61
Admitted to HD/ICA	267 (37.4)	86 (27.7)	0.00
Average LOS (SD)	6.97 (12.83)	7.75 (12.04)	0.36
LOS (median/Interquartile range)	4 (2, 7)	4 (1, 9)	0.99

Variables	MEWS <2 (n=11)	MEWS <3 (n=23)	MEWS <4 (n=47)	MEWS <5 (n=66)	MEWS <6 (n=81)
Sensitivity (%)	11.00	23.00	47.00	66.00	81.00
Specificity (%)	61.47	44.80	27.92	12.34	5.84
PPV (%)	3.00	4.31	6.66	7.53	8.52
NPV (%)	86.45	84.32	82.96	77.03	73.97
ROC area	0.52	0.62	0.68	0.66	0.68

Variables	MEWS <2 (n=174)	MEWS <3 (n=243)	MEWS <4 (n=333)	MEWS <5 (n=394)	MEWS <6 (n=420)
Sensitivity (%)	38.75	54.12	74.16	87.75	93.54
Specificity (%)	66.43	49.57	33.91	16.17	7.65
PPV (%)	47.41	45.59	46.7	44.98	44.16
NPV (%)	58.14	58.04	62.7	62.84	60.27
ROC area	0.47	0.46	0.49	0.47	0.46

Variables	Mortality (N=100)			ICU/HD/ICA Admission (N=449)
Variables	n	OR (95% CI)	P value	n	OR (95% CI)	P value
Systolic BP
Score=3	3	1.21 (0.36-4.11)	0.76	12	1.10 (0.50-2.40)	0.81
Score≥2	18	1.56 (0.90-2.69)	0.11	62	1.16 (0.80-1.67)	0.44
Score≥1	37	1.88 (1.22-2.90)	0.00	102	0.80 (0.60-1.06)	0.12
Heart rate
Score=3	15	1.42 (0.79-2.56)	0.24	35	0.51 (0.33-0.77)	0.00
Score≥2	43	2.10 (1.38-3.21)	0.00	108	0.70 (0.53-0.93)	0.01
Respiratory rate
Score=3	6	2.39 (0.95-6.00)	0.06	12	0.85 (0.40-1.78)	0.67
Score≥2	37	3.49 (2.24-5.45)	<0.001	66	0.78 (0.56-1.09)	0.15
Temperature
Score=2	5	0.80 (0.31-2.05)	0.64	22	0.69 (0.40-1.18)	0.17
Score=0	95	1.25 (0.49-3.19)	0.64	427	1.45 (0.85-2.48)	0.17
AVPU
Score=3	14	8.68 (4.14-18.22)	<0.001	21	2.77 (1.29-5.95)	0.01
Score≥2	28	8.37 (4.89-14.33)	<0.001	41	1.96 (1.19-3.23)	0.01
Score≥1	35	8.35 (5.10-13.65)	<0.001	52	1.80 (1.16-2.78)	0.01