Application of the Sherlock Mycobacteria Identification System using high-performance liquid chromatography in a clinical laboratory.

There is a growing need for a more accurate, rapid, and cost-effective alternative to conventional tests for identification of clinical isolates of Mycobacterium species. Therefore, the ability of the Sherlock Mycobacteria Identification System (SMIS; MIDI, Inc.) using computerized software and a Hewlett-Packard series 1100 high-performance liquid chromatograph to identify mycobacteria was compared to identification using phenotypic characteristics, biochemical tests, probes (Gen-Probe, Inc.), gas-liquid chromatography, and, when necessary, PCR-restriction enzyme analysis of the 65-kDa heat shock protein gene and 16S rRNA gene sequencing. Culture, harvesting, saponification, extraction, derivatization, and chromatography were performed following MIDI's instructions. Of 370 isolates and stock cultures tested, 327 (88%) were given species names by the SMIS. SMIS software correctly identified 279 of the isolates (75% of the total number of isolates and 85% of the named isolates). The overall predictive value of accuracy (correct calls divided by total calls of a species) for SMIS species identification was 85%, ranging from only 27% (3 of 11) for M. asiaticum to 100% for species or groups including M. malmoense (8 of 8), M. nonchromogenicum (11 of 11), and the M. chelonae-abscessus complex (21 of 21). By determining relative peak height ratios (RPHRs) and relative retention times (RRTs) of selected mycolic acid peaks, as well as phenotypic properties, all 48 SMIS-misidentified isolates and 39 (91%) of the 43 unidentified isolates could be correctly identified. Material and labor costs per isolate were $10.94 for SMIS, $26.58 for probes, and $42.31 for biochemical identification. The SMIS, combined with knowledge of RPHRs, RRTs, and phenotypic characteristics, offers a rapid, reasonably accurate, cost-effective alternative to more traditional methods of mycobacterial species identification.

Comparison of the MEASLESTAT M test kit with the sucrose density gradient centrifugation-hemagglutination inhibition method for detection of measles virus-specific immunoglobulin M.

A new commercial kit, MEASLESTAT M (Whittaker Bioproducts, Inc.), was compared with the sucrose density gradient centrifugation-hemagglutination inhibition method for the detection of measles virus-specific immunoglobulin M. Overall agreement between the two procedures was 97.1% for 104 single and paired serum samples tested. The sensitivity and specificity of MEASLESTAT M were 98.4 and 95.2%, respectively.

Evaluation of NCS rapid plasma reagin card test, a new screening kit for syphilis.

Agreements in qualitative and quantitative test results between the recently marketed NCS rapid plasma reagin card test (NCS Diagnostics Corp.) and the Macro-Vue rapid plasma reagin 18-mm circle card test (Hynson, Westcott and Dunning) were 99.2 and 99.1%, respectively, indicating the NCS RPR card test to be an acceptable alternative procedure for the serodiagnosis of syphilis.

Comparison of MYCOPLASMELISA with complement fixation test for measurement of antibodies to Mycoplasma pneumoniae.

The MYCOPLASMELISA test kit was compared with the complement fixation test for detection of Mycoplasma pneumoniae antibody in single sera and evaluation of acute- and convalescent-phase serum pairs for significant rises in antibody titers. Agreement between the two assays was 96.6% (85 of 88) for antibody detection and 93.9% (92 of 98) for evaluation of paired sera. Sensitivity and specificity of MYCOPLASMELISA, relative to complement fixation, for the serodiagnosis of recent M. pneumoniae infection was 92.2% (59 of 64) and 95% (19 of 20), respectively.