Viral, mycoplasmal and chlamydial lower respiratory tract infections in Hong Kong: cost and diagnostic value of serology.

A hospital virology laboratory in Hong Kong tested 10,852 sera by complement fixation (CF) for antibodies against agents of respiratory disease between 1 July 1986 and 31 December 1991. Ten commercially supplied antigens were used: influenza virus types A and B, parainfluenza virus types 1, 2 and 3, adenovirus, respiratory syncytial virus (RSV), Mycoplasma pneumoniae, Chlamydia species and Coxiella burnetii. Single sera comprised 69% of the total, including sera from 7488 patients investigated for LRTI with paired acute and convalescent samples. A total of 167 pairs (21.6%) showed rising CF titres, 82 of them against M. pneumoniae. Of the 809 patients, 365 were children under 11 years of age: 115 (31.5%) showed rising titres, including 51 with antibodies against M. pneumoniae, 21 against RSV, 17 against adenovirus and 10 against parainfluenza type 3. Viral antigen detection by immunofluorescence and virus isolation were also used: these methods yielded more positive findings than did CF test serology for the corresponding agents. The cost of the tests performed is discussed in relation to their contribution to the aetiological diagnosis of LRTI, and changes in the service to be offered are outlined.