RESEARCH imal viral replication by quantitative RT-PCR occurred by approximately day 10, but the clinical worsening seemed to lag behind this peak (3). Although we could not quanti- fy the maximal viral shedding, the maximal RT-PCR posi- tivity did fall on approximately day 10. Peiris et al. also demonstrated that an initial positive RT-PCR result had no correlation to development of an acute respiratory distress syndrome. In our multivariate analysis model, however, initial RT-PCR positivity on NPA was an independent pre- dictor for a worse outcome, rather than a previously report- ed factor, such as a coexisting condition (3–5). Although quantitative RT-PCR was not performed on samples from our patients, since the test was not available at that time, a qualitative RT-PCR result might alert the clinician to watch out for possible clinical deterioration, especially when the former test was in its infancy for common use. The relationship between viral load on NPA and outcome should be further investigated. The clinical outcomes of RT-PCR–positive patients are worse in general when compared to RT-PCR–negative patients, and their chest radiographs show more bilateral and multifocal haziness. A higher level of lactate dehydro- genase was observed in the RT-PCR–positive patients, which might indicate more extensive lung tissue injury, as indicated in other SARS patients with poor outcome (4). Whether the lower lymphocyte count in RT-PCR–positive patients suggests more extensive viral infection remains to be clarified. Use of pulsing doses of methylprednisolone could result in clinical improvement and the resolution of radiologic infiltration in some of our patients. However, its immunosuppressive effect could also predispose a patient to secondary nosocomial infection and subsequent death. How to handle negative results in RT-PCR testing is a problem. In accordance with the World Health Organization’s (WHO) recommendations, a negative result has at least two possibilities (7). First, it may indicate a false-negative result caused by low viral load or inappro- priate timing of sample collection. Second, another infec- tious or a noninfectious agent may be the cause of SARS instead of coronavirus. Finally, a negative RT-PCR result on admission may indicate early elimination of the virus by an effective and harmonious immunologic response. Serologic tests are thus important in identifying SARS infections, although the diagnosis could not be made early enough to prompt an appropriate action. In our patients, RT-PCR and serologic results were in concordance. The sensitivity of RT-PCR test was 74.7% when an antibody test was used as a standard, which can be explained by the variation in the technique and timing of sampling. The optimal timing for the RT-PCR test is unknown. The prob- lem of finding an appropriate sampling time was taken in account for the RT-PCR–positive patients with negative serologic results, since they suggested that antibodies could be detected at 21 days (8) instead of 10–14 days, as in our cohort. In addition, the PCR test may be overly sen- sitive, which may be why WHO has advised clinicians to confirm a positive RT-PCR result by repeating the test with the original sample or testing the sample in a secondary laboratory so as to increase its specificity (8). Results of both RT-PCR and antibody tests were nega- tive in eight patients; all of these patients had signs and symptoms that were clinically, radiologically, or biochem- ically well-matched with SARS, and they were given treat- ment, including ribavirin and steroid. Pulsing doses of steroid was also used in two of these patients. In addition to the sample timing, these patients could represent a milder spectrum of the disease with little antibody stimu- lation or inconspicuous coronavirus RNA level, or simply infection other than coronavirus. Antibody production may have been suppressed because of steroid administration. Because RT-PCR testing has not been standardized, the test still varies in sensitivity and specificity, and we are still confronted with a clinical dilemma in terms of infection control and management. Furthermore, the controversy of medication in the management of SARS has never been settled. Current treatment guidelines proposed by the Hospital Authority of Hong Kong are still in use despite the adverse effects of the suggested treatment (The recom- mendations were found available at: URL: http://www.ha.org.hk/hk/hesd/nsapi/?Mlval=ha_view_con tent&c_id=122711&lang=E.)Without a reliable and rapid RT-PCR test for diagnosis, patients mislabeled as having SARS will be offered treatment that they do not need. Our results indicate that a positive nasopharyngeal RT- PCR result on admission, from the current standard, should raise the possibility of SARS in appropriate clinical set- tings and should alert the clinician of the possible clinical deterioration of the patient. Furthermore, clinicians should consider repeating the qualitative RT-PCR test or perform- ing quantitative RT-PCR test for a previously RT- PCR–negative patient. Drug treatment for this group of patients may be withheld or delayed, especially if effective and reliable treatment has not been found. Acknowledgments We thank the staff of the Department of Medicine and Geriatrics, Princess Margaret Hospital for their devotion in the management of patients with severe acute respiratory syndrome in Hong Kong; and Linda Lu and Esvin Chan for their secretari- al work. Dr. Tsang is a medical officer currently working in the Infectious Disease Unit of Princess Margaret Hospital. He is responsible for the management of SARS patients during the out- break of this disease in Hong Kong. 1386 Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 9, No. 11, November 2003