Assessment of Reproducibility of Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry for Bacterial and Yeast Identification

DOI: 10.1128/JCM.00187-15

Article Figures & Data

TABLE 1

Reproducibility of organism identification at all sites after initial read of samples

Sample no.	Organism	No. identified/total no. (%) on day:					No. identified/total no. (%)	95% confidence interval (%)
Sample no.	Organism	1	2	3	4	5	No. identified/total no. (%)	95% confidence interval (%)
R1	E. aerogenes	12/12	12/12	12/12	12/12	12/12	60/60 (100)	94.0–100
R2	E. coli	12/12	12/12	12/12	12/12	12/12	60/60 (100)	94.0–100
R3	K. pneumoniae	12/12	12/12	12/12	12/12	12/12	60/60 (100)	94.0–100
R4	P. mirabilis	12/12	12/12	12/12	12/12	12/12	60/60 (100)	94.0–100
R5	P. aeruginosa	12/12	12/12	12/12	12/12	12/12	60/60 (100)	94.0–100
R6	S. aureus	12/12	12/12	12/12	12/12	12/12	60/60 (100)	94.0–100
R7	S. agalactiae	12/12	12/12	12/12	12/12	12/12	60/60 (100)	94.0–100
R8	K. oxytoca	12/12	12/12	12/12	12/12	12/12	60/60 (100)	94.0–100
R9	C. albicans	12/12	12/12	11/12	12/12	12/12	59/60 (98.3)	91.1–99.9
R10	C. glabrata	12/12	12/12	11/12	12/12	12/12	59/60 (98.3)	91.1–99.9
Total		120/120 (100)	120/120 (100)	118/120 (98.3)	120/120 (100)	120/120 (100)	598/600 (99.7)	98.8–99.9

TABLE 2

Reproducibility of organism identification at all sites after reread of samples

Sample no.	Organism	No. identified/total no. (%) on day:					No. identified/total no. (%)	95% confidence interval (%)
Sample no.	Organism	1	2	3	4	5	No. identified/total no. (%)	95% confidence interval (%)
R1	E. aerogenes	12/12	12/12	12/12	12/12	12/12	60/60 (100)	94.0–100
R2	E. coli	12/12	12/12	12/12	12/12	12/12	60/60 (100)	94.0–100
R3	K. pneumoniae	12/12	12/12	11/11^a	12/12	12/12	59/59 (100)	93.9–100
R4	P. mirabilis	12/12	12/12	12/12	11/12	12/12	59/60 (98.3)	91.1–99.9
R5	P. aeruginosa	11/12	12/12	12/12	11/12	12/12	58/60 (96.7)	88.5–99.6
R6	S. aureus	12/12	12/12	12/12	12/12	12/12	60/60 (100)	94.0–100
R7	S. agalactiae	12/12	12/12	12/12	12/12	12/12	60/60 (100)	94.0–100
R8	K. oxytoca	12/12	12/12	11/11^a	12/12	12/12	59/59 (100)	93.9–100
R9	C. albicans	12/12	12/12	12/12	12/12	12/12	60/60 (100)	94.0–100
R10	C. glabrata	12/12	12/12	12/12	12/12	12/12	60/60 (100)	94.0–100
Total		119/120 (99.2)	120/120 (100)	118/118 (100)	118/120 (98.3)	120/120 (100)	595/598 (99.5)	98.5–99.9

↵a For one of these samples, the initial read recorded no identification due to acquisition of a bad spectrum. The sample was reapplied in the same position on a new target slide and analyzed. The repeat result was recorded as the initial and only identification.

TABLE 3

Reproducibility of quality control testing at all sites after initial read and reread of samples

Organism	Initial reads		Rereads
Organism	No. identified/total no. (%)	95% confidence interval (%)	No. identified/total no. (%)	95% confidence interval (%)
S. aureus	31/31 (100)	88.8–100	31/31 (100)	88.8–100
K. oxytoca	30/30 (100)	88.4–100	29/30 (96.7)	82.8–99.9
P. aeruginosa	30/30 (100)	88.4–100	28/30 (93.3)	77.9–99.2
E. aerogenes	30/30 (100)	88.4–100	30/30 (100)	88.4–100
C. glabrata	31/31 (100)	88.8–100	31/31 (100)	88.8–100
Negative control (matrix only)	30/31 (96.8)^a	83.3–99.9	30/30 (100)	88.4–100

↵a For one of these samples, a result of mixed genera (C. pseudodiphtheriticum, T. ptyseos, B. megaterium, and S. salivarius subsp. thermophilus), which is considered unidentified, was obtained.