Laboratory practice
Choosing Positive and Negative Controls
Positive and negative controls: Which alternative explanation does each control address?
Source editorial review:
Before interpreting the result
Which alternative explanation does each control address?
- Connect negative, positive and vehicle controls to specific uncertainties.
- Record the expected response, scatter and acceptance criterion.
- Consider controls detecting interference with the readout method.
Positive and negative controls
Controls make signals interpretable by examining alternative explanations and system operation. A positive control checks an expected response under relevant conditions; a negative control helps delimit background or effects unrelated to the intervention. Their value depends on the question tested, not merely including two labels in the design.
A reading case: what to check
If the positive control fails, a candidate's absent response may be difficult to interpret. If the negative control produces signal, investigate its source before assigning specific activity. Record which alternative each control addresses and which remain open. Rather than demanding a generic control, check its relevance to the hypothesis and system.
What to preserve in the record
A responding positive control does not make the entire assay specific. The interpretation should show which possibilities were examined and which remain open.
Questions and answers
Which alternative explanation does each control address?
Controls make signals interpretable by examining alternative explanations and system operation. A positive control checks an expected response under relevant conditions; a negative control helps delimit background or effects unrelated to the intervention. Their value depends on the question tested, not merely including two labels in the design.
What should the review record preserve?
A responding positive control does not make the entire assay specific. The interpretation should show which possibilities were examined and which remain open.