TABLE 3.

Repeatability of the original ELISA method using mean of the negative pool (in OD) plus SD and the modified ELISA method

Plate B category	No. of plate A specimensa in indicated category by:
	Original method				Modified method
	Mean + 3 SD	Mean + 3-9.9 SD	Mean + >10 SD	Total	<20 CU	20-60.9 CU	≥61 CU	Total
Original method
Mean + 3 SD	35	4	11	50
Mean + 3-9.9 SD	8	29	8	45
Mean + >10 SD	5	6	74	85
Total	48	39	93	180
Modified method
<20 CU					114	2	0	116
20-60.9 CU					1	3	0	4
≥61 CU					0	0	60	60
Total					115	5	60	180

^aValues in boldface are numbers of patients with results that concur on both plates.