Background: Delayed graft function (DGF) is associated with worse short and long-term outcomes after kidney transplantation. There is a lack of biomarkers to predict outcomes in patients with DGF. Serum β2 microglobulin is a low-molecular-weight protein that correlated with creatinine but it has the advantage of measuring residual renal function in dialysis patients. In kidney transplant patients, β2 microglobulin at the time of discharge is associated with graft failure and overall mortality.  The role of the β2 microglobulin trend in patients with DGF has not been explored.

Methods: This is a retrospective study of deceased kidney transplant patients from 2013 to 2019. β2 microglobulin trend was defined as the difference between β2 on postoperative day four and β2 on postoperative day one. We used univariate and multivariate logistic regression models with level of significance of α=0.05.

Results: A total of 236 kidney recipients were reviewed, 105 (44.5%) had delayed graft function (median 9 days, 1 - 53); 50% of the patients with DGF received dialysis for one week only. The demographic and clinical characteristics of the patients with and without DGF is shown in table 1. β2 microglobulin significantly correlated with the presence of DGF (p<0.001) and significantly correlated with eGFR at 1, 3 and 6 months in all patients (p<0.001). In DGF group, β2 microglobulin trend correlated with the duration of DGF with p<0.05. This was independent of donors after circulatory death and type of kidney storage. In our cohort, β2 microglobulin was not associated with mortality or rejection.

Conclusions: The β2 microglobulin trend is a marker of kidney function useful particularly in patients with DGF, because measures the residual kidney function in the setting of dialysis. Following the trend of β2 microglobulin in patients with DGF is informative about the duration of the DGF and may help to make clinical decisions.

                                   With DGF                    Without DGF

                                   N=131                          N=105     

Age                               52.8                              51.5

African American          70.5%                          66.4%

BMI                               28.5                              27.8

Cold ischemia (hrs)      15.4                              14.3

Pump                            40.9%                          30.5%

DCD                             49.5%                          34.3%

KDPI                             62 (12-100)                 50 (2-96)

Rejection                      15.2%                          16.8%

Death                            14.3%                          14.5%