Impact of Ultrasound-guided Percutaneous Core Needle Biopsy on Biomarkers of Human Kidney Allograft Status.

BACKGROUND

Deciphering the impact of invasive percutaneous core needle biopsy of the kidney allograft on diagnostic biomarkers may help guide their clinical usage.

METHODS

We prospectively enrolled 39 adult kidney allograft recipients (patients) who underwent 41 clinically indicated, ultrasound-guided, percutaneous core needle biopsies. Pre- and post-biopsy urines were analyzed for urinary cell 3-gene signature score (UroMap), and the bloods for peripheral blood gene expression score (AlloMap Kidney) and plasma donor-derived cell-free DNA percentage (dd-cfDNA). We performed statistical analyses to compare pre- and post-biopsy values.

RESULTS

Median A260/A280 ratios of RNA from pre- and post-biopsy urines were 1.99 and 2.01, respectively; RNA yield, 0.78 versus 0.76 micrograms; and transcript copies of 18S rRNA, TGFβ1, CD3ε, CXCL10, and UroMap score were similar (all P > 0.05, Wilcoxon matched-pairs signed-rank test). The pre- and post-scores were very strongly correlated (Spearman's correlation coefficient [r s ]: 0.83, P < 0.0001). AlloMap Kidney scores in pre- and post-biopsy peripheral blood were similar ( P > 0.05) and strongly correlated (r s = 0.70, P < 0.0001). dd-cfDNA in post-biopsy plasma was higher than in pre-biopsy plasma (0.61% versus 0.26%, P = 0.004). The higher post-biopsy percentage was replicated in an independent cohort of 119 post-biopsy plasma collected from 105 patients with no rejection biopsies. To normalize the biopsy-associated increase, a correction factor of -0.36% was derived by subtracting the pre-biopsy dd-cfDNA percent from the post-biopsy percent.

CONCLUSIONS

UroMap and AlloMap Kidney scores are not affected by the biopsy procedure. However, dd-cfDNA increases following the biopsy procedure and could be normalized using the correction factor identified in this study.