Table 2.

Interassay precision

	SRR%
Serum	Mean	s.d.	Range	CV%
High TSI	446	51	331–596	11·5
Medium TSI	263	34	221–371	12·8
Low TSI	158	23	117–193	14·5
Negative	52	8	40–74	15·7

Thyroid-stimulating immunoglobulin (TSI)-containing sera of Graves' disease patients were diluted with negative control serum (negative) to yield percentage of specimen-to-reference ratio (SRR%) values near the cut-off (low), slightly higher that the cut-off (medium) and near the upper level of the TSI-Mc4 bioassay detection (high). Each sample was tested repeatedly 120 times by a single user over a period of 20 days. CV, coefficient of variation; s.d., standard deviation.