Background The standard test for the diagnosis of acute rejection in kidney transplants is the renal biopsy. Noninvasive tests would be preferable. Methods We prospectively collected 4300 urine specimens from 485 kidney-graft recipients from day 3 through month 12 after transplantation. Messenger RNA (mRNA) levels were measured in urinary cells and correlated with allograft-rejection status with the use of logistic regression. Results A three-gene signature of 18S ribosomal (rRNA)–normalized measures of CD3ε mRNA and interferon-inducible protein 10 (IP-10) mRNA, and 18S rRNA discriminated between biopsy specimens showing acute cellular rejection and those not showing rejection (area under the curve [AUC], 0.85; 95% confidence interval [CI], 0.78 to 0.91; P<0.001 by receiver-operating-characteristic curve analysis). The cross-validation estimate of the AUC was 0.83 by bootstrap resampling, and the Hosmer–Lemeshow test indicated good fit (P = 0.77). In an external-validation data set, the AUC was 0.74 (95% CI, 0.61 to 0.86; P<0.001) and did not differ significantly from the AUC in our primary data set (P = 0.13). The signature distinguished acute cellular rejection from acute antibody-mediated rejection and borderline rejection (AUC, 0.78; 95% CI, 0.68 to 0.89; P<0.001). It also distinguished patients who received anti–interleukin-2 receptor antibodies from those who received T-cell–depleting antibodies (P<0.001) and was diagnostic of acute cellular rejection in both groups. Urinary tract infection did not affect the signature (P = 0.69). The average trajectory of the signature in repeated urine samples remained below the diagnostic threshold for acute cellular rejection in the group of patients with no rejection, but in the group with rejection, there was a sharp rise during the weeks before the biopsy showing rejection (P<0.001). Conclusions A molecular signature of CD3ε mRNA, IP-10 mRNA, and 18S rRNA levels in urinary cells appears to be diagnostic and prognostic of acute cellular rejection in kidney allografts. (Funded by the National Institutes of Health and others.)

Noninvasive diagnosis and prognostication of acute cellular rejection in the kidney allograft may help realize the full benefits of kidney transplantation. To investigate whether urine metabolites predict kidney allograft status, we determined levels of 749 metabolites in 1516 urine samples from 241 kidney graft recipients enrolled in the prospective multicenter Clinical Trials in Organ Transplantation-04 study. A metabolite signature of the ratio of 3-sialyllactose to xanthosine in biopsy specimen-matched urine supernatants best discriminated acute cellular rejection biopsy specimens from specimens without rejection. For clinical application, we developed a highthroughput mass spectrometry-based assay that enabled absolute and rapid quantification of the 3-sialyllactose-to-xanthosine ratio in urine samples. A composite signature of ratios of 3-sialyllactose to xanthosine and quinolinate to X-16397 and our previously reported urinary cell mRNA signature of 18S ribosomal RNA, CD3« mRNA, and interferon-inducible protein-10 mRNA outperformed the metabolite signatures and the mRNA signature. The area under the receiver operating characteristics curve for the composite metabolitemRNA signature was 0.93, and the signature was diagnostic of acute cellular rejection with a specificity of 84% and a sensitivity of 90%. The composite signature, developed using solely biopsy specimen-matched urine samples, predicted future acute cellular rejection when applied to pristine samples taken days to weeks before biopsy. We conclude that metabolite profiling of urine offers a noninvasive means of diagnosing and prognosticating acute cellular rejection in the human kidney allograft, and that the combined metabolite and mRNA signature is diagnostic and prognostic of acute cellular rejection with very high accuracy.

Anelloviruses are DNA viruses ubiquitously present in human blood. Due to their elevated levels in immunosuppressed patients, anellovirus levels have been proposed as a marker of immune status. We hypothesized that low anellovirus levels, reflecting relative immunocompetence, would be associated with adverse outcomes in pediatric lung transplantation. We assayed blood samples from 57 patients in a multicenter study for alpha- and betatorquevirus, two anellovirus genera. The primary short-term outcome of interest was acute rejection, and longer-term outcomes were analyzed individually and as "composite" (death, chronic rejection, or retransplant within 2 years). Patients with low alphatorquevirus levels at 2 weeks post-transplantation were more likely to develop acute rejection within 3 months after transplant (P = .013). Low betatorquevirus levels at 6 weeks and 6 months after transplant were associated with death (P = .047) and the composite outcome (P = .017), respectively. There was an association between low anellovirus levels and adverse outcomes in pediatric lung transplantation. Alphatorquevirus levels were associated with short-term outcomes (ie, acute rejection), while betatorquevirus levels were associated with longer-term outcomes (ie, death, or composite outcome within 2 years). These observations suggest that anelloviruses may serve as useful biomarkers of immune status and predictors of adverse outcomes.

Comparisons of perceived barriers to adherence in pediatric and adolescent SOT have not been systematically conducted despite association between medication non-adherence and poor outcome. Fifteen centers in CTOT-C enrolled patients in a cross-sectional study. Subjects' guardians completed the PMBS and subjects over eight completed the Adolescent Scale (AMBS). Association of three identified PMBS factors and subject age was assessed. Secondary analyses assessed associations between PMBS, AMBS, and patient demographics. Three hundred sixty-eight subjects or their guardians completed PMBS or AMBS. A total of 107 subjects were 6-11 yr; 261 were ≥12. Unadjusted and propensity-adjusted analyses indicated higher perceived barriers in guardians of adolescents as compared to guardians of pre-adolescents medication scheduling and frustration domains regardless of organ (p < 0.05). PMBS and AMBS comparisons revealed that guardians reported fewer ingestion issues than patients (p = 0.018), and differences appeared more pronounced within younger responders for scheduling (p = 0.025) and frustration (p = 0.019). Screening revealed guardians of older patients report increased perceived barriers to adherence independent of socioeconomic status. Guardians of adolescents reported fewer perceived barriers to ingestion/side effects than patients themselves, particularly in pre-adolescents (8-11 yr). Brief screening measures to assess perceived barriers should be further studied in adherence improvement programs.

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