High Coefficient of Variation at Lower Standard Curve

Symptom

Replicate measurements at the bottom of the standard curve (highest OD values, lowest analyte concentrations) show excessive variability with high coefficient of variation (CV) between replicates.

1. 1 Higher OD values inherently demonstrate greater variance in competitive ELISA format
2. 2 Sample concentrations falling in less precise region of standard curve
3. 3 Pipetting imprecision amplified at low analyte concentrations
4. 4 Insufficient replicates to adequately assess variance at curve extremes

1. 1 Increase the concentration range of standard curve to shift lower concentrations toward middle range
2. 2 Dilute samples less to position measured values in the middle of the standard curve
3. 3 Use calibrated precision pipettes and perform careful technique at low concentrations
4. 4 Increase number of replicates (≥3) for samples near curve endpoints to improve statistical reliability

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