Identification and validation of urinary CXCL9 as a biomarker for diagnosis of acute interstitial nephritis
Journal of Clinical Investigation, 2023
Moledina D., Obeid W., Smith R., Rosales I., Sise M., Moeckel G., Kashgarian M., Kuperman M., Campbell K., Lefferts S., Meliambro K., Bitzer M., Perazella M., Luciano R., Pober J., Cantley L., Colvin R., Wilson F., Parikh C.
| Disease area | Application area | Sample type | Products |
|---|---|---|---|
Nephrology | Patient Stratification | Urine |  Olink Target 96 |
Abstract
Background. Acute tubulointerstitial nephritis (AIN) is one of the few causes of acute kidney injury with diagnosis-specific treatment options. However, due to the need to obtain a kidney biopsy for histological confirmation, AIN diagnosis can be delayed, missed, or incorrectly assumed. Here, we identify and validate urinary CXCL9, an IFN-γ-induced chemokine involved in lymphocyte chemotaxis, as a diagnostic biomarker for AIN.
Methods. In a prospectively enrolled cohort with pathologist-adjudicated histological diagnoses, termed the discovery cohort, we tested the association of 180 immune proteins measured by an aptamer-based assay with AIN and validated the top protein, CXCL9, using sandwich immunoassay. We externally validated these findings in 2 cohorts with biopsy-confirmed diagnoses, termed the validation cohorts, and examined mRNA expression differences in kidney tissue from patients with AIN and individuals in the control group.
Results. In aptamer-based assay, urinary CXCL9 was 7.6-fold higher in patients with AIN than in individuals in the control group (P = 1.23 × 10–5). Urinary CXCL9 measured by sandwich immunoassay was associated with AIN in the discovery cohort (n = 204; 15% AIN) independently of currently available clinical tests for AIN (adjusted odds ratio for highest versus lowest quartile: 6.0 [1.8–20]). Similar findings were noted in external validation cohorts, where CXCL9 had an AUC of 0.94 (0.86–1.00) for AIN diagnosis. CXCL9 mRNA expression was 3.9-fold higher in kidney tissue from patients with AIN (n = 19) compared with individuals in the control group (n = 52; P = 5.8 × 10–6).
Conclusion. We identified CXCL9 as a diagnostic biomarker for AIN using aptamer-based urine proteomics, confirmed this association using sandwich immunoassays in discovery and external validation cohorts, and observed higher expression of this protein in kidney biopsies from patients with AIN.