Highly sensitive proximity mediated immunoassay reveals HER2 status conversion in the circulating tumor cells of metastatic breast cancer patients

Table 3 Characteristics of CEER vs. Other Commonly Used Immunoassays

	CEER	Reverse Phase Protein Array	PhosphoFlow	ELISA
Sample Protein Requirement	Native proteins	Denatured proteins	Fixed proteins	Native or Fixed proteins
Minimum Cell Requirement (Assay Sensitivity)	1 cell	2500~15000 cells	1 × 10⁴~1 × 10⁶ cells	150 to 300 cells
Multiplex Format	One sample, multiple analytes	Multiple samples, one analyte	One sample, multiple analytes (limited)	Multiple samples, one analyte
Assay Specificity	• High	• Low	• Low	• Medium
Advantages of Assay	• Simultaneous analysis of multiple analytes (e.g. selected analytes of a signaling pathway) on a single sample. • Suitable for clinical samples of rare cells as well as limited solid tissue samples.	• Simultaneous analysis of multiple samples for a single analyte. • Suitable for samples of cells or solid tissue.	• Detection of target molecules within a cell population in one sample. • Suitable for blood sample analysis.	• High throughput.
Disadvantages of Assay	• Screening compatible antibody sets for each target.	• Need to print each sample; not suitable for applications in clinical samples from individual patients. • Cross reaction of detector antibody.	• Not suitable for rare cell analysis or solid tissue samples. • Requires a large number of cells. • Requires samples in single cell suspension, limiting its use.	• Low sensitivity requires large numbers of cells. • Not suitable for rare cell analysis.

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