Table 4.

Association between CMV IgM antibody level and low IgG avidity^a

IgM UA/ml	No. of sera (total = 324)	% low avidity
IgM negative or equivalent, <0.90	154	1.9
0.90–1.09	50	6.0
1.10–1.29	26	15.4
1.30–1.49	29	17.2
1.50–1.99	32	40.6
≥2.00–4.00	33	78.8

^aSera are listed by increasing levels of IgM antibody, showing the proportion that were low IgG avidity. Chi-square test for trend, P < 0.0001. The 0.7 avidity test cutoff was used to define low IgG avidity.