(19%) reported having recently traveled to SARS-endemic areas in the 2 weeks before admission; the most common areas visited were in the southern part of China. Our cohort consisted of patients (46.8%) from a local housing estate, the Amoy Gardens. Ten patients (4.6%) had one or more coexisting medical problems: diabetes mellitus (3 cases), a history of cerebrovascular disease (4 cases), ischemic heart disease (3 cases), chronic rheumatic heart disease (1 case), hypertrophic obstructive cardiomyopathy (1 case), sick sinus syndrome (1 case), cirrhosis of the liver secondary to chronic hepatitis B (1 case), bronchiectasis (1 case), end- stage renal disease (1 case), Sjögren syndrome (1 case), and nasopharyngeal carcinoma (1 case). The proportions of patients from Amoy Gardens that were RT-PCR positive (48%) and negative (45.7%) were not significantly differ- ent (p = 0.76). Likewise, the proportions of healthcare workers (p = 0.28) or patients with coexisting conditions (p = 0.83) did not differ significantly. RT-PCR Results NPA samples for RT-PCR were taken from all patients at admission; samples from 156 patients (71.6%) were positive. The mean time from disease onset to sample col- lection was 4.4 ± 2.3 days. No significant difference in the mean sampling time was found between RT-PCR–positive or –negative patients. The optimal time for sample collec- tion was day 8–10 when 13 of 14 patients (92.9%) were positive (Figure). Symptoms and Laboratory Findings The most common clinical features for both RT- PCR–positive and –negative cases included fever, chill, malaise, myalgia, cough, rigor, and headache (Table 1). Shortness of breath and dizziness were significantly high- er in RT-PCR–positive patients in bivariate analysis. Vital signs taken on admission (temperature, heart rate, and sys- tolic and diastolic blood pressure) were similar between the two groups. Common laboratory findings included anemia with hemoglobin level <12 g/dL (14.7%), lym- phopenia with leukocyte count <4 x 109/L (72%), throm- bocytopenia with platelet count <150 x 109/L (52.3%), hypokalemia with plasma potassium level <3.5 mmol/L (41.3%), hyponatremia with plasma sodium level <135 mmol/L (61.5%), and elevated levels of lactate dehydroge- nase >230 U/L (46.6), alanine transaminase > 40 U/L (30.8%), and C-reactive protein (77.8%). By bivariate analysis, lymphopenia and elevated lactate dehydrogenase level on admission were significantly different between RT-PCR–positive and –negative patients (Table 2). Serologic Test Results Eighty-seven NPA RT-PCR–positive patients and 33 RT-PCR–negative patients had serologic tests on their RESEARCH Figure. Percentage of reverse transcription polymerase chain reaction (RT-PCR) positivity at different times of sample collection after onset of symptoms. paired serum samples 10–14 days apart. Of the positive RT-PCR patients, 74 patients (85.1%) had total antibodies detected by IFA, while serologic tests for 25 patients (75.8%) in the RT-PCR–negative group were positive. Results for 13 patients in the RT-PCR–positive group and 8 patients in the RT-PCR–negative group were negative. Radiologic Findings Initial chest radiographs for 210 patients (96.3%) were abnormal. Sixty-five (41.7%) RT-PCR–positive patients and 13 (21%) RT-PCR–negative patients had bilateral chest involvement shown by radiograph. Multifocal radio- logic involvement was found in 74 (47.4%) RT-PCR–pos- itive patients and 15 (24.2%) RT-PCR–negative patients. By bivariate analysis, RT-PCR–negative patients were less likely to have abnormal bilateral (p = 0.01) and multifocal (p = 0.003) radiographs. Outcomes The overall 30-day mortality rate was 10.1% (22 patients). Fifty-two (23.9%) patients required intensive- care unit (ICU) admission, and 43 patients (19.7%) need- ed mechanical ventilation. In nine (4.1%) patients, acute renal failure further complicated SARS. When compared to the RT-PCR–negative patients, the RT-PCR–positive patients were more likely to need treatment in the ICU (p = 0.002), require mechanical ventilation (p = 0.008), and die (p = 0.044) (Table 3). Predictors of Mortality Admission parameters, including epidemiologic data, vital signs, and laboratory and chest radiographic findings, were analyzed separately. By bivariate analysis, factors associated with death were age >60 (p = 0.037), male sex (p = 0.007), major coexisting medical conditions (p = 0.001), shortness of breath (p = 0.005), total leukocyte count >4.0 x 109/L (p = 0.041), bilateral chest radiographic involvement (p = 0.046), RT-PCR positivity on NPA sam- ples (p = 0.034), and pulsing doses of steroid (p = 0.001). Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 9, No. 11, November 2003 1383