4th Congress of the Spanish Society of TransplantationKidney transplantationUrinary Clara Cell Protein in Kidney Transplant Patients: A Preliminary Study

- Proximal tubular dysfunction is highly prevalent in KT patients.
- Urinary excretion of CC16, a new tubular marker of proximal tubular dysfunction, is elevated in the renal transplant population.
- Urinary excretion of CC16 is directly associated with urinary levels of other markers of tubular injury, such as β2m and NAG.

ObjectiveThe aim of this exploratory study was to analyze the urinary excretion of Clara cell protein (CC16), a new marker of proximal tubular dysfunction (PTD), in kidney transplantation (KT).Materials and MethodsUrinary concentrations of CC16, β2-microglobulin (β2m), and N-acetyl-glucosaminidase (NAG) were measured in 50 KT patients (72% men; mean age 50.4 ± 12.4 years; diabetes in 24%; duration of KT 4.3 ± 3.1 years) and 10 healthy controls (6 men; mean age 33.6 ± 13.4 years).ResultsUrinary levels of β2m, NAG, and CC16 were significantly higher in KT patients than in controls: β2m: 0.77 (interquartile range [IQ] 0.22 to 4.62) g/g vs 0.069 (IQ 0.05 to 0.10) g/g; NAG: 3.16 (IQ 2.09 to 5.33) U/g vs 1.73 (IQ 1.25 to 2.07) U/g; CC16: 26.01 (IQ 8.62 to 123.3) g/g vs 2.51 (IQ 0.83 to 7.18) g/g (P < .001). Elevated levels of β2m, NAG, and CC16 were found in 81%, 28%, and 71% of KT patients, respectively. Urinary levels of β2m, NAG, and CC16 significantly increase as glomerular filtration rate (GFR) decreases. Interestingly, in patients with GFR >60 mL/min, we still found high levels of β2m, NAG, and CC16 in 77%, 13%, and 52%, respectively. Diabetic subjects had significant higher levels of the 3 markers compared with nondiabetic subjects, without differences in albumin excretion or GFR. CC16 showed a positive correlation with urinary albumin (r = 0.42, P < .001), NAG (r = 0.352, P < .05), and β2m (r = 0.75, P < .001).ConclusionPTD is highly prevalent in KT patients. This is the first study that analyzes CC16 in KT patients, showing that the urinary excretion of this protein is significantly increased in this population. Further studies are needed to examine the clinical value of CC16 in KT patients.