Evaluation of non-contrast MRI biomarkers in lupus nephritis.

Objectives: To investigate the association of novel non-contrast MRI biomarkers with standard measurements of renal function and renal disease activity in lupus.

Methods: A pilot study of lupus nephritis (LN) and lupus non-nephritis (LNN) patients, and healthy volunteers (HV), was undertaken. Multi-modal renal MRI was performed including sequences for arterial spin labelling (ASL) measuring blood flow, diffusion tensor imaging (DTI), measuring microstructural disruption, and effective transverse relaxation time (T2*) which is a biomarker of micro-haemorrhage. MRI measurements were compared with urinary protein creatinine ratio (uPCR) and estimated glomerular filtration rate (eGFR) measurements in the whole study population, then differences in imaging measurements between the groups were explored.

Results: 21 patients (6 LN, 8 LNN and 7 HV) completed the study, although ASL data were not available in 4 subjects. In the whole cohort, eGFR correlated significantly with the apparent diffusion coefficient measurement from DTI in the medulla (r=0.47, p=0.03). uPCR correlated strongly with the fractional anisotropy (FA) DTI measurement in the cortex and moderately with T2* measurements (rho=-0.71, p<0.001 and rho=-0.53, p=0.013, respectively). Delayed blood flow to the medulla was found in LN subjects and there was a trend towards lower FA values in the cortex, suggesting micro-structural disruption (p=0.04 and p=0.07, respectively).

Conclusions: This preliminary study demonstrates that non-contrast renal MRI biomarkers are associated with standard measures of disease activity in lupus. The potential utility of these non-invasive biomarkers warrants further investigation, as there is an unmet need for reliable biomarkers of disease activity in lupus nephritis.