Abstract: The invention relates to the field of diagnosis of epithelial-to-mesenchymal transition (EMT), such as mesothelial-to-mesenchymal transition (MMT), in particular EMT of the peritoneum, which often occurs upon peritoneal dialysis. The invention provides a method and kit based on markers comprising at least one extracellular matrix protein, e.g., collagen 13, collagen 6, and/or keratin 34, at least one protein involved in building and/or restructuring of extracellular matrix, e.g., matrix metalloproteinase 1, at least one protein involved in cell-cell and/or cell-matrix contacts, e.g., cadherin 13 or thrombospondin 1, at least one growth factor, e.g., VEGF, and, optionally, at least one BMP antagonist, e.g., Gremlin 1.