Technical and Biological Replicates

The Assay Guidance Manual defines technical replicates in relation to measurements of the same sample and distinguishes within-run from between-run repetitions. Changing the day can provide information about temporal variation without automatically creating a new biological sample. Technical document.

In a hypothetical example, rereading the same extract examines instrumental consistency. Preparing another extract from the same material adds another stage of variation, but still does not necessarily mean incorporating an independent organism or donor.

NC3Rs defines the experimental unit by its ability to receive an intervention independently. In animal research, it can be an individual, a group or part of an organism, depending on the design. An animal always equals one unit is therefore not a universal rule either. Guidance on units.

The practical question is which elements could receive different conditions without a shared application determining their exposure. That level must be identified before the available observations are counted.

Lazic and colleagues distinguished these three levels and examined publications involving parental interventions and observations in offspring. Their investigation showed that measuring several individuals did not, by itself, establish where the relevant replication occurred. Methodological study.

The entity of interest may be an organism; the intervention may be applied to a group; and observations may come from several parts of each individual. Naming those levels provides more information than labeling all of them biological replicates.

Consider a hypothetical example with wells originating from the same cell preparation. Some wells might receive independent interventions but still share an origin. Inference about those interventions and inference about variation between donors would not be the same question.

It is therefore insufficient to count containers or insist that every well is technical. The report must explain preparation, allocation and the population about which it aims to conclude. It should also preserve relationships between observations when several share the same origin.

A useful description states how many biological origins there were, how many units received each condition and how many readings were obtained per unit. It then explains what each figure point represents and how repetitions were combined.

This breakdown allows readers to assess which variation was measured and which was outside the study. A total number of readings can describe analytical work, but it should not replace the number of units supporting the scientific comparison.