Clinical Biochemistry Definitions
Key formulas and definitions used in clinical biochemistry and laboratory quality control.
Inaccuracy (Bias)
Inaccuracy = Bias = (Laboratory Value - True Value)
Inaccuracy % = Bias % = [(Laboratory Value - True Value) × 100] / True Value
Note: True Value may be "EQAS Mean of Comparison".
Imprecision
Imprecision = CV% = (IQC-SD × 100 / IQC-Mean)
Total Error
Total Error % (TE %) = (Bias % + 2CV%)
Total Error (TE) = (Bias + 2SD)
Standard Deviation Index
Standard Deviation Index = SDI = (IQC Value - IQC Mean) / IQC-SD
Z Score
Z Score = (EQAS Value - EQAS Mean of Comparison) / EQAS-SDPA
Factor of The Analyte
Factor of The Analyte = Concentration of Calibrator / (O.D. of Calibrator - O.D. of Blank)
Concentration of Substrate / Analyte
Concentration of Substrate / Analyte = (O.D. of Substrate - O.D. of Blank) × Concentration of Calibrator / (O.D. of Calibrator - O.D. of Blank)
Concentration of Substrate / Analyte = (O.D. of Substrate - O.D. of Blank) × Factor
Delta OD
Delta OD = (OD at 60 second) - (OD at 0 Second) = Difference of OD in 60 Second (1 minute) interval
Note: In case of kinetic or End-Point kinetic method, Delta OD will be used instead of OD