Evaluation of triage methods used to select patients with suspected pandemic influenza for hospital admission: cohort study.

BACKGROUND: Triage methods are necessary in emergency departments to provide clinicians with a reliable method for determining each patient's risk of adverse outcome. Prior to the 2009 H1N1 influenza pandemic the CURB-65 (a risk prediction score for pneumonia, based on confusion, urea level, respiratory rate, blood pressure and age over 65 years) pneumonia score and the Pandemic Modified Early Warning Score (PMEWS) were used to assess adults. In response to the emergence of the pandemic, national guidance produced a new swine flu hospital pathway for use adults and children. However, none of these methods had been widely validated or tested in the setting of pandemic influenza.

OBJECTIVES: To use the initial waves of the 2009 H1N1 pandemic to evaluate existing triage methods in patients presenting with suspected pandemic influenza, and to determine whether an improved triage method could be developed.

METHODS: A prospective cohort study was undertaken of patients with suspected swine flu presenting to four hospitals during the second wave of the 2009 H1N1 pandemic. Staff completed a standardised assessment form that included the CURB-65 score, PMEWS and the swine flu hospital pathway. Patients who died or required respiratory, cardiovascular or renal support during the 30-day follow-up were defined as having a poor outcome. Patients who survived to 30 days without requiring respiratory, cardiovascular or renal support were defined as having a good outcome.

RESULTS: Data were collected and analysed from 481 cases across three hospitals. Most of the cases were children, with 347 out of 481 (72%) aged 16 years or less. There were five poor outcomes: two deaths and three survivors who required respiratory support. The five patients with poor outcomes had CURB-65 scores of zero, one (three cases) and two, and PMEWS scores of one, five, six, seven and eight. The swine flu hospital pathway was positive in three out of five cases. The C-statistic for each method was CURB-65 0.78 [95% confidence interval (CI) 0.58 to 0.99], PMEWS 0.77 (95% CI 0.55 to 0.99) and the swine flu hospital pathway 0.70 (95% CI 0.45 to 0.96). Patients with a higher CURB-65 score were more likely to be admitted (p < 0.001): 25 out of 101 (25%) with a score of zero, 11 out of 24 (46%) with a score of one, 7 out of 8 (88%) with a score of two, and the patient with a score of three were admitted. Admitted patients had a higher mean PMEWS score (4.6 vs 2.0, p < 0.001). The C-statistics for CURB-65, PMEWS and the swine flu hospital pathway in adults in terms of discriminating between those admitted and discharged were 0.65 (95% CI 0.54 to 0.76), 0.76 (95% CI 0.66 to 0.86) and 0.62 (95% CI 0.51 to 0.72) respectively.

LIMITATIONS: The 2009 H1N1 pandemic was much smaller and less severe than predicted and resulted in a lack of sufficient data.

CONCLUSIONS: Potential concerns were raised about the use of existing triage methods for patients with suspected pandemic influenza, as these methods may fail to discriminate between patients who will have an adverse outcome and those with a benign course. Clinicians in the study did not generally appear to admit or discharge on the basis of these methods, despite their recommended use. Further research is required to evaluate existing triage methods and develop new triage tools for suspected pandemic influenza.