Monoclonal gammopathies (MGs) represent a diverse group of plasma cell disorders that range from asymptomatic premalignant conditions to aggressive malignancies such as multiple myeloma (MM). Mass spectrometry (MS) based serum analysis offers a non-invasive, highly sensitive alternative to conventional techniques for identifying and quantifying M-proteins. It enables more precise assessment of treatment response and residual disease, particularly in patients with suspected complete response (CR), those not eligible for bone marrow procedures, or those treated with monoclonal antibodies that may interfere with standard assays. This guideline document, endorsed by the Spanish Society of Laboratory Medicine (SEMEDLAB) and the Spanish Society of Hematology (SEHH), provides comprehensive recommendations for the clinical and analytical application of MS in the detection and monitoring of M-proteins in patients with MGs. The document outlines optimal use of MS at diagnosis, during follow-up, and in reporting practices, with a focus on standardized implementation, interpretative criteria, and clinical decision-making support.

Background: Daratumumab-based regimens represent the gold-standard therapy for newly diagnosed AL amyloidosis patients. However, there are few studies about the efficacy of this treatment in real life. Methods: This study included 99 patients: 27 (27.3%) received daratumumab and proteasome inhibitor-based schemes, 46 (46.4%) were treated with proteasome inhibitors and/or immunomodulator-based regimens, and 26 (26.3%) were treated with chemotherapy. Results: Patients receiving daratumumab and proteasome inhibitor-based regimens achieved higher rates of partial haematological responses or better (100.0% vs. 78.3% vs. 58.3%; p = 0.009 and p < 0.001) and complete responses (74.1% vs. 37.0% vs. 12.5%; p = 0.003 and p < 0.001) than the proteasome inhibitors and/or immunomodulators and chemotherapy groups, respectively. Daratumumab and proteasome inhibitor-based schemes resulted in a shorter time to haematological response (1 month to partial response or better and 4 months to complete response). Moreover, in the group treated with daratumumab and proteasome inhibitor-based regimens, there was a trend of obtaining better and faster organ responses. The benefit of daratumumab and proteasome inhibitor-based regimens was that they resulted in an improvement in progression-free survival (not reached) compared to the proteasome inhibitor and chemotherapy groups (18 months; p = 0.022 and 6 months; p = 0.002). In addition, the clinical benefit was consistent in patients with Mayo Clinic stages III–IV. Conclusions: This study supports the efficacy and superiority of adding daratumumab to the frontline treatment over proteasome inhibitor-based regimens and chemotherapy in AL amyloidosis, including in advanced cardiac disease.