Are the World Health Organisation case definitions for severe acute respiratory distress syndrome sufficient at initial assessment?

Abstract

Introduction: On March 13, 2003, Singapore doctors were alerted about an outbreak of atypical pneumonia that became known as severe acute respiratory syndrome (SARS). We now describe a series of patients that did not fit World Health Organisation (WHO) case definitions for SARS at initial assessment.

Methods: The Ministry of Health, Singapore centralised SARS cases in the study hospital and its emergency department (ED) became the national screening centre. A screening questionnaire and a set of admission criteria based on WHO case definitions were applied. Patients discharged from ED were tracked via telephone surveillance and recalled if necessary. A retrospective review was done of patients who did not fit WHO definitions initially, were discharged and had re-attended.

Results: During the outbreak, 11,461 people were screened for SARS. Among 10,075 (87.9 percent) discharged from the ED, there were 28 re-attendees diagnosed to have SARS later, giving an undertriage rate of 0.3 percent. Among the 28, six (21.4 percent) did not complain of fever and 22 (78.6 percent) had temperatures less than 38.0 degrees Celsius during their first ED visit. One patient was screened to have all three criteria but during consultation, the contact history was found to be unrelated to the known "hot spots". The initial mean temperature was 37.6 degrees Celsius (standard deviation [SD] 0.8), which increased significantly (p-value equals 0.04) to 38.0 degrees Celsius (SD 0.8) during their subsequent visit. Chest radiographs with infective changes increased significantly (p-value equals 0.009) from 16 percent to 52.4 percent over the two ED visits.

Conclusion: The WHO case definitions were helpful in evaluating majority of SARS patients initially. However under-triage at ED is inevitable, with a 0.3 percent under-triage in our study population. In this group and asymptomatic individuals who came for screening, a tracking and recall system helped to ensure their timely return to the ED.