TABLE 3.

Within- and between-run precision (CV) and accuracy (bias)^a

Antibiotic and nominal concn (mg/liter)	Within run (n = 12)			Between run (n = 24)
	Mean measured concn ± SD (mg/liter)	CV (%)	Bias (%)	Mean measured concn ± SD (mg/liter)	CV (%)	Bias (%)
AMX
2b	2.03 ± 0.07	3.2	1.5	2.09 ± 0.30	14.2	4.7
6	5.69 ± 0.14	2.5	−5.2	6.15 ± 0.52	8.4	2.5
30	29.46 ± 1.10	3.7	−1.8	29.87 ± 2.21	7.4	−0.4
70	70.40 ± 4.98	7.1	0.6	69.75 ± 6.56	9.4	−0.4
PIP
2b	2.11 ± 0.04	2.1	5.3	2.07 ± 0.23	11.3	3.5
6	5.97 ± 0.15	2.4	−0.4	6.20 ± 0.43	6.9	3.4
30	30.06 ± 1.05	3.5	0.2	30.59 ± 1.95	6.4	2.0
70	71.54 ± 4.84	6.8	2.2	72.28 ± 5.43	7.5	3.3
OXA
2b	2.12 ± 0.04	1.8	5.9	2.07 ± 0.25	12.1	3.3
6	5.96 ± 0.13	2.1	−0.6	6.29 ± 0.45	7.2	4.8
30	29.28 ± 1.03	3.5	−2.4	30.94 ± 1.78	5.8	3.1
70	67.75 ± 4.63	6.8	−3.2	69.98 ± 5.64	8.1	0.0
CLX
2b	2.12 ± 0.06	2.6	6.0	2.06 ± 0.25	12.2	2.9
6	5.90 ± 0.13	2.2	−1.6	6.37 ± 0.37	5.8	6.2
30	29.15 ± 1.01	3.5	−2.8	31.22 ± 1.58	5.1	4.1
70	68.72 ± 4.62	6.7	−1.8	70.84 ± 5.38	7.6	1.2
FEP
2b	2.12 ± 0.04	2.0	5.9	2.09 ± 0.25	12.2	4.4
6	6.10 ± 0.12	2.0	1.6	6.13 ± 0.51	8.2	2.2
30	30.27 ± 1.02	3.4	0.9	30.33 ± 2.38	7.9	1.1
70	70.93 ± 4.72	6.6	1.3	73.27 ± 4.67	6.4	4.7
CAZ
2b	2.11 ± 0.04	2.1	5.5	2.03 ± 0.26	12.9	1.5
6	5.94 ± 0.13	2.2	−1.1	6.14 ± 0.43	7.1	2.3
30	32.86 ± 1.45	4.4	9.5	31.07 ± 2.29	7.4	3.6
70	70.02 ± 5.01	7.2	0.0	71.44 ± 4.44	6.2	2.1
CTX
2b	2.12 ± 0.04	2.1	6.2	1.99 ± 0.26	13.2	−0.4
6	6.11 ± 0.13	2.1	1.8	6.22 ± 0.43	7.0	3.7
30	30.01 ± 1.03	3.4	0.0	30.98 ± 1.84	5.9	3.3
70	70.53 ± 4.80	6.8	0.8	70.79 ± 6.31	8.9	1.1
CFZ
2b	2.23 ± 0.05	2.2	11.4	2.09 ± 0.25	12.1	4.7
6	6.19 ± 0.12	2.0	3.1	6.42 ± 0.47	7.4	7.0
30	30.04 ± 1.01	3.3	0.1	31.05 ± 1.70	5.5	3.5
70	70.89 ± 4.79	6.8	1.3	70.68 ± 6.30	8.9	1.0

^aCV, coefficient of variation; AMX, amoxicillin; PIP, piperacillin; OXA, oxacillin; CLX, cloxacillin; FEP, cefepime; CAZ, ceftazidime; CTX, cefotaxime; CFZ, cefazolin.

^bConcentration corresponding to the LLOQ.