There is a possibility that renal dysfunction may potentially reduce the diagnostic power of the laboratory parameters Tn, NT-proBNP and sFLC levels, used in the current prognostic classification of AL amyloidosis and the diagnosis of heart involvement by amyloid. In this study, the impact of lowering the eGFR value on the usefulness of these parameters in the prognosis and diagnosis of the presence of amyloid in the myocardium was assessed in a group of 71 patients with newly diagnosed primary amyloidosis. The assessment of diagnostic power of laboratory parameters was performed on the entire study group, and in the ranges of eGFR ≥ 60 and < 60 mL/min/1.73 m2. It has been proven that, with a decrease in the eGFR value, the concentrations of NT-proBNP and the κ uninvolved light chains increase significantly (p < 0.001). To assess the diagnostic power of laboratory parameters used in the diagnosis of myocardial involvement in patients with AL amyloidosis, an ROC analysis was performed. The highest values of AUC were obtained for the NT-proBNP concentration (AUC = 0.906). The lowest values of the AUC and Youden's index were obtained for the dFLC values (AUC = 0.723), and involved κ FLC concentration (AUC = 0.613). For all compared parameters, the smallest values of the AUC were obtained for eGFR (<60 mL/min/1.73 m2). It seems that the most suitable cardiac parameter used in the prognostic classification of AL amyloidosis, independent of renal function, is TnI. It should be noted that a concentration of involved λ chains hada higher diagnostic power to assess the heart involvement, compared to the routinely used "cardiac parameters", TnI and NT-proBNP. It can therefore be an additional parameter used to assess the presence of amyloid in the myocardium. A decrease in eGFR value influenced the change in the diagnostic cut-off points of the most analyzed laboratory parameters. Finally, it is concluded that lowering the eGFR value reduces the utility of laboratory parameters used in the prognostic classification of AL amyloidosis.
Keywords: Kumar’s classification; eGFR; immunoglobulin free light chains; primary AL amyloidosis.