Appropriate control samples are critical to the development of any flow cytometry assay, but access to appropriate control samples can be especially challenging for clinical specimens. What kind of samples can be used for evaluating immuno-oncology or vaccine trials? Consider these factors when selecting an appropriate control.

1. What is your sample? Are you looking a peripheral blood or tissue? It is generally easy to gain access to peripheral blood from healthy controls, but if you are developing an assay that looks at cells from tissues or organs, control samples can be more difficult to obtain, so surrogate tissues or blood may need to be used.
   
   
2. What is the disease or abnormal state? For most clinical studies, you will not have healthy samples from participants as they will be diagnosed with a disease or disorder at the time of enrollment. But, if you are developing an assay to evaluate a novel immunotherapy to treat a specific hematological malignancy or autoimmune disorder, you will likely be dependent on using peripheral blood from healthy controls. In contrast, if you are doing a vaccine study, blood samples taken from healthy participants prior to vaccination are suitable control.
   
   
3. What are the cells you are studying? Are you studying a relatively abundant cell type like T cells or are you looking at a rare subset of dendritic cells? Developing assays with healthy control samples for abundant cell types may be easier than rare cell types, because you must typically have a greater pool of cells to work with when studying rare cell types. Rare cell types can be hard to track in experimental samples as well and can make or break the success of your assay.

Controls are at the core of any reliable flow cytometry assay. Be sure to consider what characteristics your control sample must satisfy and how accessible control samples are in order to select an appropriate control.