Table 3. Clinical progress and outcome on day 30 after admission Positive RT-PCR for coronavirus Negative RT-PCR for coronavirus Clinical progress/outcome n=156 (%) n=62 (%) Patients requiring ICU care 46 (29.5) 6 (9.7) Patients requiring mechanical ventilation 38 (24.4) 5 (8.1) Patients developing acute renal failure 8 (5.1) 1 (1.6) Death 20 (12.8) 2 (3.2) aFisher exact test was applied if number was <5; RT-PCR, reverse transcription polymerase chain reaction. RESEARCH p value 0.002 0.008a 0.451a 0.044a Discussion In general, the epidemiologic background, clinical presentation, laboratory findings, and radiologic findings of our patients were similar to those of other reports (3–5). The clinical features of our cohort were rather nonspecific, with fever, chills, malaise, and myalgia being the most common. Radiologic features of our patients were similar- ly nonspecific. Anemia, lymphopenia, and thrombocytope- nia were common on admission. These symptoms might reflect peripheral consumption or bone marrow suppres- sion by the infection. Elevation of alanine transaminase, C- reactive protein, and lactate dehydrogenase levels was fre- quently observed; this finding might indicate extensive tis- sue damage. Currently, the definition of SARS is mainly clinical, and diagnosis is made by exclusion of pneumonia from other known causal agents. However, patients with similar clinical scenarios may not be infected by the same agent, and placing them in the same location may spread infec- tion. Unfortunately isolating every patient is not possible, especially with a large cohort. An early, rapid, and reliable test is needed. After coronavirus was recognized as the putative agent for SARS, diagnostic tests have burgeoned rapidly over the past 2 months. However, serologic tests cannot offer an early diagnosis since, despite their remark- able specificity, they require approximately 3 weeks for the total antibodies to become detectable (2). Electron microscopy and viral culture are not sensitive and conven- ient enough for general use. Inevitably, clinical character- istics are used solely for the diagnosis of SARS, despite the condition’s nonspecific nature. RT-PCR for coronavirus on NPA samples appears to be the best supportive test for an early and firm diagnosis. However, the sensitivity of this test varies, and standardi- zation of the test has not been unified. The test we used was qualitative and had good sensitivity (71.6%). In our study, the mean time between onset of symptoms and sam- ple collection was 4.3 days. Peiris et al. reported that the sensitivity for RT-PCR was 32% at a mean 3.2 days after onset (3). In our study, the best time for sampling was on days 8 to 10 after onset of symptom. During that period, >90% of the samples were positive. However, since the condition of SARS patients deteriorated both clinically and radiologically during this time, waiting 8–10 days to make a firm diagnosis or to plan for appropriate therapy is not possible (3). The mean time of sample collection did not differ significantly between RT-PCR–positive or –neg- ative patients, suggesting that the difference in outcomes between these two groups could not be explained by the discrepancy in the duration of their symptoms before admission. Whether the difference in primers used in the RT-PCR testing or infection by a another agent, such as metapneumovirus or Chlamydia species (6), could also contribute to the discrepancy in sensitivity is not known. Peiris et al. reported that the sensitivity of stool samples for RT-PCR tests was 97% (mean of 14.2 days) (3). In our study, the overall positive rate was 30%. However, RT- PCR was performed on stool specimens only when diar- rhea developed in patients. Inconsistency in the timing of sample collection might also contribute to the low positive rate. In patients with negative RT-PCR results on NPA samples, none had a stool sample positive by RT-PCR. Hence, RT-PCR on stool specimen could not provide an early diagnosis of coronavirus infection in our cohort. Patients with a positive RT-PCR result on admission had adverse outcomes in term of survival, ICU care, and assisted ventilation, when compared to patients with nega- tive RT-PCR results. Therefore, the patients with over- whelming disease had more viral shedding, which may have been more readily detected. Despite the satisfactory sensitivity that we demonstrated, the test might not provide the information for quantitative analysis. Hence, a nega- tive result might not represent low viral load in patients and vice versa. A quantitative RT-PCR could give us some idea as to the correlation between the viral concentration and disease progression. Peiris et al. reported that the max- Table 4. Multivariate analysis on risk factors associated with 30-day mortalitya Risk factors Adjusted OR (95% CI) Significant coexisting conditions 13.4 (3.1 to 58.2) Shortness of breath on admission 3.9 (1.2 to 12.3) Total leukocyte count >4.0 x109/L at admission 6.94 (1.18 to 41.6) Positive RT-PCR on NPA 6.4 (1.1 to 38.0) Use of pulsing doses of steroid 26.0 (4.4 to 154.8) aOR, odds ratio; CI, confidence interval; RT-PCR, reverse transcription polymerase chain reaction; NPA, nasopharyngeal aspirates. p value 0.001 0.020 0.033 0.038 0.001 Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 9, No. 11, November 2003 1385