BACKGROUND: Posttransplant lymphoproliferative disorder (PTLD) is a severe complication of solid organ transplantation (SOT). However, there is no consensus on PTLD screening methods. Gammopathies (GP), which occur in 10-25% of SOT recipients, have been linked to subsequent development of PTLD. Therefore, GP detection methods, such as serum protein electrophoresis (SPE), serum protein immunofixation (SIFE), urine protein immunofixation (UIFE) and the quantitative measurement of serum free light chains (SFLC) are candidate methods for PTLD screening. OBJECTIVE: We aimed to assess the frequency of PTLD and GP, association of GP with subsequent PTLD, allograft loss or death and the diagnostic performance of SPE/SIFE in PTLD screening. The main objective was to explore, whether GP detection methods can be used to enhance the efficiency of PTLD screening and to formulate a concise algorithm for posttransplantation (post-Tx) follow-up. METHODS: We performed a cohort study on 1677 SOT recipients with SPE/SIFE data who underwent kidney, liver, heart, pancreas, Langerhans islets or multiple organ transplantation at the Institute of Clinical and Experimental Medicine between 1966 and 2015. The median (IQR) of follow-up time was 8.0 (4.0-12.0) years. RESULTS: The frequencies of PTLD and GP in SOT recipients were 2.8% and 6.4%, respectively. The frequencies of transient GP, GP of undetermined significance and malignant GP were 33%, 63% and 4% respectively. The median time between SOT and GP detection was 2.0 (interquartile range 1.0-7.0) years. GP was associated with a significantly higher risk of PTLD, allograft loss and death, with hazard ratios (95% confidence intervals) of a 6.06 (2.51-14.64), 2.61 (1.49-4.6) and 1.99 (1.2-3.3), respectively. Additionally, GP was associated with 2.98-fold increased risk of allograft loss in kidney transplant patients. SPE diagnostic sensitivity and specificity for PTLD were 14.8% and 93.9%, respectively. PTLD was diagnosed more often and earlier if SPE/SIFE was included in the post-Tx follow-up. CONCLUSIONS: GP after SOT is associated with a high risk of PTLD, allograft loss and poor survival. The combination of SPE, SIFE, SFLC and UIFE is optimal for GP detection. These methods aid in identifying patients who are at risk for PTLD or allograft damage and should be included in regular post-Tx follow-up.

3rd Faculty of Medicine Charles University Ruská 2411 87 Prague Czech Republic

3rd Faculty of Medicine Charles University Ruská 2411 87 Prague Czech Republic; Department of Laboratory Methods Institute for Clinical and Experimental Medicine Vídeňská 1958 9 Prague Czech Republic

Department of Laboratory Methods Institute for Clinical and Experimental Medicine Vídeňská 1958 9 Prague Czech Republic

Department of Neurobiology Care Sciences and Society Division of Clinical Geriatrics Karolinska Institutet Neo Blickagången 16 Sweden

Department of Organ Harvesting and Transplantation Databases Institute for Clinical and Experimental Medicine Vídeňská 1958 9 Prague Czech Republic

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