What is the primary concern when evaluating instrument carryover in flow cytometry?

When evaluating instrument carryover in flow cytometry, the primary concern focuses on the reliability of high-sensitivity assays. Carryover refers to the unintended transfer of cells, particles, or reagents from one sample to the next, which can lead to inaccurate results, particularly in assays that require high sensitivity. In high-sensitivity applications, even minimal carryover can produce significant false positives or skew quantitative values because the detection limits are very close to the background signal. Therefore, ensuring that the instrument is free from carryover is crucial for obtaining trustworthy data, especially when assessing low-abundance populations or rare events in complex biological samples.

The other options, while relevant to the overall integrity and performance of flow cytometry, do not directly address the critical aspect of how carryover impacts the sensitivity and specificity of assays. While contamination, reference values, and reagent freshness are all important factors in maintaining assay quality, the core concern specific to carryover revolves around the precision and accuracy necessary for high-sensitivity measurements.