UNDETECTABLE LUTEINIZING-HORMONE LEVELS USING A MONOCLONAL IMMUNOMETRIC ASSAY

Previous studies have shown wide discrepancies among the results obtai ned with different immunometric assays. We present five cases (out of 4000 women) whose plasma luteinizing hormone was not detected using a LH immunometric assay (LH Stratus Baxter) but was recognized by other kits. These cases concerned one 28-year-old woman presenting with infe rtility and four postmenopausal women. The LH Amerlite kit gave detect able but low results. The results obtained with the other kits were >7 IU/l. FSH levels were >7 IU/l. In one case, sera were taken before an d after the menopause, differences between the LH results increased. D iscrepancies among LH assays kits have been attributed to variation bo th in standard curve calibration and in epitope specificity of the kit monoclonal antibodies. The Baxter kit might misrecognize some isoform s present in postmenopausal women. The present data illustrate the pot ential false results with such immunoassays in routine clinical labora tory testing. When undetectable LH results are not clinically explaine d or when disparities between LH and FSH are observed, we suggest usin g a second methodology or a bioassay if necessary. Improvement in LH a ssays and standardization might resolve the problem of discrepancies b etween the bH results.