TABLE 3.

Concordance between conventional phenotypic biochemical identification and MALDI-TOF MS identification for the retrospective analysis and prospective analysisa

Analysis type and phenotypic biochemical identification parameterRetrospective MALDI-TOF analysis (no. of isolates) Prospective MALDI-TOF analysis (no. of isolates)
Species IDGenus IDNo IDMisidentificationTotalSpecies IDGenus IDMajor errorMinor errorNo IDNo uniform IDTotal
Retrospective
    Species identification26320105298
    Genus identification733013
    No ID10023
    Misidentification910313
    Total for group280241310327
Prospective
    Species ID783261202814
    Genus ID991701231132
    Major error75003015
    Minor error111020014
    No ID2100205
    Total for group9025011683980
  • a Isolates were tested in duplicate by MALDI-TOF MS and by conventional methods according to manufacturers descriptions (Vitek, API, and bioMerieux) both retrospectively and prospectively. For MALDI-TOF analysis, species identification (score of >2.0), genus identification (score of <2.0 but >1.7), major error (incorrect genus), minor error (correct genus with incorrect species), no identification (score of <1.7) and nonuniform identifications between duplicates were scored. Misidentification applies to either the genus or species level. ID, identification.