BACKGROUNDTo clarify the difference and significance of T-lymphocyte subsets in differential diagnosis between severe acute respiratory syndrome SARS) and common atypical pneumonia.

METHODSTotally 100 patients hospitalized in Beijing Ditan Hospital since March to June 2003 with clinical diagnosis of SARS were involved in this study. These patients courses of disease were over 3 weeks. These patients were divided into two groups, SARS group and common atypical pneumonia group (non-SARS group). The counts of CD3+, CD4+ and CD8+ T-lymphocyte of two groups were systematically recorded and analyzed.

RESULTSSixty-five of the patients were confirmed to have common type of SARS, including 26 males and 39 females, 50 cases received methylprednisolone treatment. Thirty-five cases had common atypical pneumonia (non-SARS), 21 were males while 14 were females, 20 cases received methylprednisolone treatment. All the cases of two groups were cured in the end. The SARS patients T-lymphocyte counts decreased first and then increased. Before 15 days of disease course, mean CD3+, CD4+, CD8+ T-lymphocyte counts of SARS patients were decreased apparently (694+/-568/microl, 441+/-356/microl, 309+/-462/microl). After 15th day of disease course, the counts gradually returned to normal CD3+, CD4+, CD8+ T-lymphocyte counts of non-SARS patients were normal. Compared with patients of the same group who were not treated with glucocorticoids, T-lymphocyte counts of non-SARS patients treated with glucocorticoids had no obvious difference. But glucocorticoids had some effect on SARS patients recovery of cellular immune function, i.e., it delayed the recovery by about 6 days.

CONCLUSIONWith or without treatment with glucocorticoids,the lowered CD3+, CD4+, CD8+ T-lymphocyte counts in the early stage are of very important significance in differential diagnosis between severe acute respiratory syndrome and common atypical pneumonia.