What is the frequency of false positive and false negative results, and how are they dealt with?
All tests produce false positive and false negative results and these need to be assessed for clinical significance. Reference ranges have been developed in collaboration with The Mayo Clinic and include individuals up to 90 years of age. Some of these individuals have minor degrees of renal impairment. This increases the concentrations of the FLCs, and the κ/λ ratios, and is apparent on a κ/λ log plot. The difference between the normal and abnormalsamples is then selected using standard deviations from the mean. If all of the 282 normal samples in the Mayo Clinic study are used, this represents four standard deviations from the mean and is greater than normally chosen cut off levels. Therefore, test samples outside this range will most likely indicate patients with monoclonal gammopathies. Negative sFLC results occur in a few patients with NSMM, AL amyloidosis and LCDD. Also, rare patients have monoclonal proteins in the urine detected only by IFE. The molecular form of these FLC mole
