Interference of Luteinizing Hormone b-Core Fragment in Urinary

Iles et al. (1) speculated on the value of development of a specific assay to measure human luteinizing hormone b-core fragment (hLHbcf) without cross-reactivity with human chori-onic gonadotropin b-core fragment (hCGbcf). We wish to draw readers’ attention to the fact that we devel-oped and reported such a specific assay for hLHbcf in 1995 (2) and reviewed the applications of this as-say in 1996 (3). We wrote (3) that the assay “may have useful applications in tumor marker assays, pregnancy tests, and menopause”. The hLHbcf assay (B505-B503*) exhibits 1 % cross-reactivity with hLH and 0.1 % cross-reactivity with hCGbcf. We found that the assay detects the urinary form of hLHbcf in the urine of nor-mally ovulating women (2). We ap-plied this assay to the urine of post-menopausal women and found significant quantities of hLHbcf but not hCGbcf. The mean concentration of hLHbcf for 107 samples from post-menopausal women was 236 pmol/g creatinine (4). We also measured hCGbcf in the same samples and found that its concentration was one-tenth that of hLHbcf. For hCGbcf, we used our laboratory assay B210-B108 * (5), which has 2 % cross-reac-tivity with hLHbcf. These data sug-gest that to use hCGbcf as a cancer marker, an assay of very high speci-ficity for this molecule is required because of possible cross-reaction with hLHbcf. We observed in our work that hLHbcf cross-reacted with polyclonal antisera to hLH, suggesting that uri-nary ovulation test kits that measure intact hLH have the potential for sim-ilar hLHbcf cross-reactions if they are based on polyclonal antibodies or monoclonal anti-hLH antibodies that cross-react with hLHbcf. If such should be the case, then the day of ovulation as predicted by the kit could be in error. The results presented by Iles et al. (1) supported our data published in 1995 (2), 1996 (3), and 1998 (4). It is important to emphasize the potential risk of hLHbcf cross-reactivity in urine when related gonadotropins (e.g., hLH, hLHb, hCG, hCGb, and hCGbcf) are measured