Soluble interleukin-2 receptor (sIL-2R) levels in renal transplantation: Comparison between clinical and laboratory analysis

Soluble interleukin-2 receptor levels (sIL-2R) were retrospectively evaluated in 43 consecutive kidney transplant recipients (22 males, 21 females), from day 0 up to 90 days after transplantation. 11 pts were on CsA only, 13 on CsA+MP and 19 on CsA+MP+Aza. All graft-worsening episodes were then retrospectively analyzed, either according to clinical criteria only, or taking into account sIL-2R levels. On clinical grounds, 50 rejections were observed: 'a posteriori' 5 turned out to be either infections or non-immunological worsenings of graft function (prevalence of misdiagnosis in the rejection set: 5/50, 10%). Of the 8 infections, 2 were actually treated as rejections (margin of error: 2/8, 25%). CsA toxicity was correctly diagnosed in 2/4 episodes. The analysis based on sIL-2R levels increase confirmed the clinical diagnosis in 52/79 cases (66%). The prevalence of misdiagnosis was: 21.2% in rejection, 2/3 in CsA toxicity, while infections were overestimated in 60% of cases. Isolated sIL-2R level increase was not associated with rejection in 87.5% of cases, while an associated increase of IL-2R and plasma creatinine had a 5% chance of being wrong. SIL-2R levels increased before any rise in plasma creatinine in late rejections (28±21 days after transplantation), while they increased after the rise of plasma creatinine in early rejections (10±5 days) (p=0.014). In the rejection set, sIL-2R had a sensitivity of 83.4%, a specificity of 80%, a positive predictive value of 50.2% and a negative predictive value of 95.2%. SIL-2R determination does not provide superior results to those obtained with clinical tools (p=0.15). Nevertheless, sIL-2R may help in predicting rejections occurring later than the 15th post-transplant day, or in disclosing subclinical episodes of smouldering infection and immunological activation.