Free light chain and intact immunoglobulin abnormalities in heart transplant recipients: Two year follow-up timelines and clinical correlations

•The dynamics of the serum free light chain (sFLC) concentration reflects the immunosuppressant regimen.•Intact immunoglobulin and sFLC pathologies after heart transplantation are frequent and mostly transient.•The SPE and sFLC methods provide different diagnostic information.•The etiology behind the sFLC pathologies is multifactorial.•Renal impairment can cause the misinterpretation of the sFLC kappa/lambda ratio.

ObjectivesTo assess the timelines of serum free light chain (sFLC) concentrations and the kappa/lambda light chain (K/L) ratio in heart transplant (HTX) recipients. To analyze the performance of serum protein electrophoresis (SPE), serum immunofixation (sIFE) and sFLC measurements for gammopathy detection following a HTX.MethodsA total of 96 patients who underwent a HTX were analyzed during a two-year follow-up period. The relevant clinical data were obtained from patient medical records. SPE, sIFE and sFLC methods were used for the detection of free light chain and intact immunoglobulin gammopathies at 4 time points after HTX.ResultsA statistically significant decrease in sFLC K and L (a decrease of 39.1% and 27.6%, respectively, when compared to pretransplant values) was found 9 months after the HTX (p < 0.001, Friedman test). We detected SPE or sIFE abnormalities in 23 (8.4%) samples, and sFLC K/L ratio abnormalities in 34 (12.4%) samples. All of the K/L ratio abnormalities had normal SPE/sIFE values, and 19% of the findings were persistent.ConclusionsA significant and consistent dynamics in the sFLC concentration was found in the HTX patients during a 2-year follow-up period, which reflected changes in the immunosuppressant dosage. A remarkable number of monoclonal and polyclonal gammopathies was identified with some persistent abnormalities, using the SPE/sIFE and sFLC methods. Some of the detected abnormalities, which might possess a higher risk for PTLD if interpreted according to common practice in nonTX patients can only be detected by sFLC methods.