[Practical evaluation of rapid diagnostic tests for mycobacteriosis and virus infection]

Because cultures of mycobacteria and viruses take a great number of days, the results are delayed in these clinical laboratory tests. For this reason, rapid diagnostic tests without these cultures are required. Among the laboratory tests of mycobacteria, acid-fast stain as a rapid diagnostic test is the first to give significant information to laboratory staffs and physicians. There are mainly two procedures, directly smearing clinical specimens and smearing concentrated specimens treated with NALC-NaOH on slide glass. The former is performed for specimens from emergency patients. When a patient is suspected of tuberculosis, a DNA-amplification test such as COBAS AMPLICOR TEST (PCR test) is performed for directly detecting Mycobacterium tuberculosis in clinical specimens, regardless of whether the specimens show positive or negative by acid-fast stain. Sixty-one of 1,023 specimens tested in Showa University Fujigaoka Hospital in February 2000-May 2002 were found positive by both PCR and culture tests. Fourteen were found negative by PCR test and positive by culture test. Five were found positive by PCR test and negative by culture test. Alternatively, MTB-64 (Capilia TB) is a kit for rapidly identifying M. tuberculosis using colonies. The time necessary for completion of the test was approximately 15 minutes per sample. In our study, the identification test showed weak-positive for 2 strains of M. marinum (ATCC927 and one clinical isolate), compared with positive for 28 clinical isolates and strain H37Ra of M. tuberculosis. Recently, rapid diagnostic kits for detecting various pathogenic viruses have been developed. The kits for detecting influenza virus are in especially great demand with the spread of newly-developed antiviral agents. There was an epidemic of the type A virus in the winters 2001-2002. 101 (32%) of 316 clinical specimens tested in the hospital were found positive with InfluA. B-Quick [SEIKEN] (Denka) or Directigen Flu A (Becton Dickinson). These kits showed high utility. Also, Abbot TESTPACK RSV (Dainabot) for detecting RS virus and ROTALEX DRY (Orion Diagnostica) for detecting rotavirus showed high utility. However, these rapid diagnostic kits have weak points: high costs, false positives and false negatives. Thus, more improvements are required.