Editor—We report a similar experience at the National University Hospital, Singapore, to that of Rainer et al in Hong Kong's New Territories.1
We screened patients for severe acute respiratory syndrome (SARS) by using criteria from the World Health Organization and transferred suspect and probable cases to Tan Tock Seng Hospital, the country's designated SARS hospital, for further management. Patients with undifferentiated fever or respiratory symptoms who did not meet WHO criteria (and would not be accepted at Tan Tock Seng Hospital due to the limited resources available) were monitored in isolation rooms with daily blood counts, chest radiography, and temperature monitoring every four hours without antipyretic drugs until an alternative diagnosis was established.
From 17 March to 16 May 2003 we isolated 909 patients and transferred 47 patients directly to Tan Tock Seng Hospital for evaluation (table). Thirteen of the 18 patients with SARS treated at our hospital did not initially meet the WHO criteria. WHO criteria when applied at presentation had a sensitivity of 27.8% (95% confidence interval 9.7% to 53.5%) and a specificity of 95.5% (94.0% to 96.8%). We found a much lower positive predictive value (10.6%) than Rainer et al, as expected given the lower prevalence at a general hospital rather than a specialised SARS screening centre. Our data reaffirm that even during an epidemic, many patients may have atypical presentations2 and require a period of careful observation under isolation until the clinical course is manifest or WHO criteria are met. They also highlight the urgent need for a rapid diagnostic test that can be applied early in the course of the infection especially if SARS reappears next winter.
Table 1.
Accuracy of WHO criteria for SARS in a general teaching hospital. Values are numbers of patients
| SARS (n=18) | Non-SARS (n=938) | Total (n=956) | |
|---|---|---|---|
| Initial WHO criteria met | 5 | 42 | 47 |
| Initial WHO criteria not met | 13 | 896 | 909 |
Sensitivity 27.8% (95% confidence interval 9.7% to 53.5%), specificity 95.5% (94.0% to 96.8%), positive predictive value 10.6% (3.6% to 23.1%), negative predictive value 98.6% (97.6% to 99.2%).
Kee-Seng Chia, associate professor of community medicine, National Univerity of Singapore, and Yean-Teng Lim, chairman of the medical board, National University Hospital, are also authors of this letter.
Competing interests: None declared.
References
- 1.Rainer TH, Cameron PA, DeVilliers S, Ong KL, Ng AWH, Chan DPN, et al. Evaluation of WHO criteria for identifying patients with severe acute respiratory syndrome out of hospital. BMJ 2003;326: 1354-8. (21 June.) [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Fisher DA, Lim TK, Lim YT, Singh KS, Tambyah PA. Atypical presentations of SARS. Lancet 2003;361: 1740. [DOI] [PubMed] [Google Scholar]