Comparison between visual assessment and digital image analysis in evaluating renal interstitial fibrosis in lupus nephritis

Abstract

<h3>Background</h3> Prediction of the renal outcomes is crucial for patients with lupus nephritis due to high morbidity and mortality. Renal interstitial fibrosis is correlated with progression to renal failure. However evaluation of interstitial fibrosis by subjective visual assessment comparing with digital image analysis has not been well studied. <h3>Method</h3> All kidney core biopsies diagnosed with lupus nephritis at Chiang Mai University hospital during July 1 2011 to December 31 2012 were retrieved from the database. Interstitial fibrosis in percentage was assessed on scanned Picrosirius red-stained histological images (Aperio) using software analysis. Visual assessment was performed under a light microscope by two pathologists (SS, SL). Clinical, laboratory data and renal outcomes [dialysis, doubling of serum creatinine (DSC), end-stage renal disease (ESRD) and complete remission (CR)] were collected retrospectively from the time of biopsy to the last follow-up. <h3>Result</h3> Interstitial fibrosis evaluating by digital image analysis (IF-IA) showed better intraobserver (Pearson correlation coefficient: r=0.98, <i>p</i><0.001) and interobserver reliability (r=0.79, <i>p</i><0.001) compared with interstitial fibrosis evaluating by visual assessment (IF-VA) (intraobserver reliability: r=0.85, <i>p</i><0.001 and interobserver reliability: r=0.61, <i>p</i>=0.001) while IF-VA was more negatively correlated with baseline estimated glomer-ular filtration rate (r=-0.50, <i>p</i>=< 0.001) compared with IF-IA (r=-0.235, <i>p</i>=0.034). A significantly greater degree of interstitial fibrosis evaluated by visual assessment was observed in patients with subsequent dialysis, DSC and ESRD; and a significantly lesser degree of interstitial fibrosis was observed in patients with CR compared with patients without these outcomes. There is no difference in IF-IA between patients with and without such renal outcomes. IF-VA but not IF-IA was positively correlated with incidence of dialysis, DSC and ESRD [Spearman correlation coefficient (rs)=0.309, 0.366, 0.459 and p=0.005, 0.001, <0.001, respectively] and was negatively correlated with CR (rs=-0.306, <i>p</i>=0.005). For Kaplan-Meier survival analysis, IF-VA greater than percentile 75th (P75, interstitial fibrosis=20%) had significantly higher incidence of dialysis, DSC and ESRD and significantly lower incidence of CR compared with IF-VA lesser than P75. However IF-IA had no difference. <h3>Conclusion</h3> Renal interstitial fibrosis evaluating by digital image analysis is more reliable and precise, however assessing by visual assessment is more predictive of renal outcomes in lupus nephritis patients.