TABLE III. Precision and accuracy data of back calculated concentrations of calibration samples for isoniazid (INH) in plasmaa .

Analyte	Nominal concentration (ng/mL)	Observed concentration (ng/mL - mean ± SD)	Precision (RSD) (%)	Accuracy (%)
INH	100	97.28 ± 3.32	3.41	97.28
	200	208.10 ± 15.31	7.36	104.05
	500	503.12 ± 43.11	8.57	100.62
	1,000	1.071.81 ± 10.44	0.97	107.18
	2,000	1.967.41 ± 18.50	0.94	98.37
	5,000	4.994.55 ± 179.65	3.60	99.89
	7,500	6.934.19 ± 488.77	7.05	92.46

a: two replicates per batch; RSD: relative standard deviation; SD: standard deviation.