TABLE 2.

Comparison of titers 1/2 or 1 dilution greater in endpoint of frozen banked sera from undocumented and documented cases of syphilis, tested with CDC synthetic VDRL antigen and with CDC and BDMS reference VDRL antigens

Syphilis category	No. of specimens
	Total	With CDC synthetic VDRL antigen higher	With natural VDRLa antigen higher	With CDC synthetic and natural VDRL antigen endpoints equal
Undocumented	100	85	0	15
Documented
Untreated
Primary	9b	3	2	4
Secondary	20	20	0	0
Latent	6c	4	0	1
Treated
Primary	15d	10	0	2
Secondary	30	30	0	0
Latent	20e	17	1	0
Total	200	169	3	7

^aNatural VDRL antigen was either CDC reference VDRL (undocumented serum samples) or BDMS VDRL antigen (documented sera). 

^bOne sample was nonreactive with TP-PA but reactive with both VDRL antigens. 

^cOne sample was reactive with TP-PA but nonreactive with both VDRL antigens. 

^dOne sample was reactive with TP-PA but nonreactive with both VDRL antigens, and two samples were nonreactive with TP-PA and both VDRL antigens. 

^eOne sample was reactive with TP-PA but nonreactive with both VDRL antigens, and one sample was nonreactive with TP-PA and both VDRL antigens.