TABLE 3.

Laboratory scores and classification for each 16S rRNA gene PCR quality control series

Laboratory no.	Result for bacterial extract, expected responsea				Result for clinical specimen, expected response				Scoreb	Classc
	E1, S. epidermidis	E2, P. acnes	E3, negative	E4, S. aureus	S1, primary arthroplasty, negative	S2, hip prosthesis, S. agalactiae	S3, ankle osteitis, P. aeruginosa	S4, knee prosthesis, S. dysgalactiae
QC 1d
L1	+	+	−	+	−	+	+	+	8/8	Optimal
L2	+	+	−	+	−	+	FN	+	7/8	Acceptable
L3	+	+	FP	+	−	+	+	+	7/8	To be improved
L4	+	+	−	+	−	+	+	+	8/8	Optimal
L5	+	+	Unint.	+	−	+	+	+	7/8	Acceptable
L6	+	+	−	+	−	FN	+	+	7/8	Acceptable
	E5, S. lugdunensis	E6, negative	E7, E. faecalis	E8, H. influenzae	S5, primary arthroplasty, negative	S6, knee prosthesis, E. cloacae	S7, spondylodiscitis, S. aureus	S8, hip prosthesis, P. mirabilis
QC 2
L1	+	FP	+	+	−	+	+	+	7/8	To be improved
L2	+	−	+	+	−	+	+	+	8/8	Optimal
L3	+	Unint.	+	+	−	+	+	+	7/8	Acceptable
L4	+	−	+	+	−	+	FN	+	7/8	Acceptable
L5	+	−	+	+	−	+	+	+	8/8	Optimal
L6	+	−	+	+	−	+	+	+	8/8	Optimal
L7	+	−	+	+	−	+	+	+	8/8	Optimal
	E 9, C. striatum	E10, S. haemolyticus	E11, negative	E12, M. morganii	S9, tibia osteitis, S. epidermidis	S10, knee prosthesis, S. agalactiae	S11, spondylodiscitis, S. oralis	S12, primary arthroplasty, negative
QC 3
L1	+	+	−	+	+	+	+	−	8/8	Optimal
L2	+	+	−	+	FN	+	+	−	7/8	Acceptable
L3	+	+	−	+	+	+	+	−	8/8	Optimal
L4	+	+	−	+	+	+	+	Unint.	7/8	Acceptable
L5	+	+	−	+	+	+	+	−	8/8	Optimal
L6	+	+	−	+	+	+	+	−	8/8	Optimal
L7	+	+	Unint.	+	+	+	+	−	7/8	Acceptable

^a+, true positive, −, true negative; FN, false negative; FP, false positive; Unint., uninterpretable result.

^b(Number of true positives + number of true negatives)/number of samples.

^cOptimal, all results were correct; acceptable, 1 FN; to be improved, ≥2 FN or 1 FP.

^dLaboratory 7 did not participate in the first QC.