Preinjection skin testing is necessary for the use of cross-linked bovine collagen as 3 % of patients will have a hypersensitivity reaction. However, a negative result does not completely eliminate the risk of an allergic reaction. Leonard et al describe a small subset of patients who developed antibovine collagen antibodies who had negative preinjection skin testing. While those patients became seropositive the clinical relevance is unclear. In only one of those patients a local reaction occurred which may have been immunogenic. 2
2. Leonard MP , Decter A , Hills K , Mix LW . Endoscopic subureteral collagen injection: are immunological concerns justified? J Urol 1998 ; 160 : 1012 – 16 .