%0 Letter %T Navigating between perpendicular drop and tangent skimming methods for M-protein quantification: a call for clarification of guidelines. %A Cabo J %A Favresse J %J Clin Chem Lab Med %V 62 %N 3 %D 2024 Feb 26 %M 37773954 %F 8.49 %R 10.1515/cclm-2023-0730