What are the cons of membrane permeability assays?

Cons of membrane permeability assays:

• Membrane permeability assays only provide information about the integrity of the cell membrane, without directly assessing other aspects of cellular health, such as metabolic activity or functional status.
• Temporary membrane disruption or transient changes in permeability resulting from certain experimental conditions may give false positive results. 
• Calcein is sensitive to buffers containing esterases
• Calcein staining and propidium iodide staining cannot be combined with fixation protocols
• Apoptotic cells retain their membrane integrity and are resistant to exclusion dyes.
• Light sensitive