Traditional testing methods for monoclonal protein in Plasma Cell Dyscrasias correctly identify a majority of patients. However, limitations in these methods can cause patients to be missed at diagnosis. Furthermore, difficulties in traditional methods of measuring monoclonal proteins have restricted the ability to measure M-proteins at low levels thereby limiting the laboratory and the clinician, particularly in identifying patients who have minimal residual disease.
In the past decade, assays which can measure immunoglobulin free light chains has improved detection of patients with Multiple Myeloma and related diseases, as well as providing a more sensitive tool for measuring a patients response to therapy. However, that assay is limited in that not all patients with monoclonal gammopathy show abnormal free light chain measurements. Within the last year, a novel assay which can identify and quantitate individual immunoglobulin heavy chain/light chain pairs has received FDA approval. Like Immunofixation, this assay has the ability to identify m-protein heavy chain and light chain isotypes. However, unlike Immunofixation, the heavy chain/light chain combination assay is quantitative and provides information which is independent of complicating factors such as changes in hematocrit. This heavy chain/light chain combination assay shares with the free light chain assay the ability to measure the analyte in normal individuals, providing exquisite sensitivity when measuring patients in relapse or with minimal residual disease.
The heavy chain/light chain combination assay is not intended to replace the free light chain assay but rather provides complementary information which enhances the laboratorys ability to provide quantitative information on M-protein production. Utilizing both assays,will enhance the ability of the laboratory and the clinician to evaluate patient tumor load at diagnosis and in response to therapy.