TABLE 4.

Concordance between MALDI-TOF MS and standard identification methods across major organism categories^a

Match category	Result (% concordance [95% confidence interval])
	Gram-positive cocci	Gram-positive rods	Gram-negative cocci	Gram-negative rods				Overall
				Enteric	Nonfermenting	Fastidious	Overall
Speciesb	123/126 (97.6% [93.2–99.5])	87/89 (97.8% [92.1–99.7])	20/20 (100% [83.2–100])	154/160 (96.3% [92.0–98.6])	70/72 (97.2% [90.3–99.7])	52/53 (98.1% [89.9–100])	292/302 (96.7% [94.0–98.4])	522/537 (97.2% [95.4–98.4])
Genusc	131/131 (100% [97.2–100])	93/93 (100% [96.1–100])	22/22 (100% [84.6–100])	159/160 (99.4% [96.6–100])	74/74 (100% [95.1–100])	53/53 (100% [93.3–100])	305/306 (99.7% [98.2–100])	551/552 (99.8% [99.0–100])
No reliable identificationd	1/1 (100% [25–100])	6/6 (100% [54.1–100])	1/1 (100% [25–100])	0/0	2/3 (66.7% [9.4–99.2])	3/4 (75% [19.4–99.4])	5/8 (62.5% [24.5–91.5])	13/16 (81.3% [54.4–96])
Total	132	99	23	160	77	57	314	568

^aThe distribution of identifications by match category was not significantly different across the major organism categories (P = 0.247, chi-square test).

^bNumber of isolates concordant to species level with standard method identification/total number of isolates scoring ≥1.9.

^cNumber of isolates concordant to genus level with standard method identification/total number of isolates scoring ≥1.7. Isolates scoring <1.7 were considered unreliable for identification by MALDI regardless of their concordance with standard method identification.

^dNumber of isolates concordant to genus level with standard method identification/total number of isolates scoring <1.7. Isolates scoring <1.7 were considered unreliable for identification by MALDI regardless of their concordance with standard method identification.