Table 1.

A comparison of TBII and biological assays.

	TBII assays	Biological assays
Advantages	Freely available commercially	Differentiate between stimulating and blocking activities of TRAb
	Relatively cheap
	Easy to perform
	Sensitive 2nd-3rd generation assays available
Disadvantages	Do not differentiate between stimulating and blocking activities of TRAb	Most are technically complex and time consuming
	Lack absolute correlation with clinical phenotype	Relatively expensive
	No correlation with severity of illness
	Lack predictive value for GD outcome

TBII are easy to perform, cheap and are highly sensitive. They remain the preferred assay method of choice in clinical practice. Bioassays have the ability to differentiate between stimulating and blocking TRAb, but the utility of this property in day-to-day clinical practice is unclear. Furthermore, they require greater technical expertise to perform and currently are more expensive.