TABLE 3.

Evaluation of different MALDI-TOF MS Hib/non-Hib classification methods

Results by no. of spectra for:	Hib (n = 33)	Non-Hib (n = 77)	Sensitivity (%)a	Specificity (%)a	AU-ROCb	Reproducibility (%)c
ClinProTools
6 spectra			100	98.7	0.994	97.6
Hib	33	1
Uncertain	0	0
Non-Hib	0	76
2 spectra			100	97.4	0.987	100
Hib	33	2
Non-Hib	0	75
Biotyper MSPs:
Regular
6 spectra			100	98.7	0.994	90.5
Hib	33	0
Uncertain	0	1
Non-Hib	0	76
2 spectra			100	97.4	0.987	95.2
Hib	33	2
Non-Hib	0	75
Subtyping
6 spectra			97.0	100	0.985	92.9d
Hib	32	0
Uncertain	1	0
Non-Hib	0	77
2 spectra			100	100	1.000	100d
Hib	33	0
Non-Hib	0	77
Specially designed
6 spectra			81.8	100	0.909	76.2
Hib	27	0
Uncertain	3	0
Non-Hib	3	77
2 spectra			97.0	98.7	0.978	85.7
Hib	32	1
Non-Hib	1	76

^aSensitivity and specificity were calculated based on the results from the original laboratory (Malmö).

^bArea under the receiver operator characteristic curve calculated based on correct or false result from the measurements with the microflex instrument compared to those with PCR. All uncertain isolates were considered falsely identified. AU-ROC values were calculated using SPSS Statistics 22.0 (IBM, Armonk, NY).

^cReproducibility was calculated as the percentage of isolates MALDI-TOF MS measured on both the microflex and ultrafleXtreme instrument, which were identified to the same category (Hib, uncertain, or non-Hib) on both instruments.

^dReproducibility with adjusted cutoff.