Assessing the disease specificity of urinary PF4 for active lupus nephritis

Abstract

Abstract Background The use of urinary biomarkers is particularly helpful in avoiding invasive procedures such as renal biopsy. We recently observed that urinary Platelet factor 4 (PF4) was elevated in patients with active lupus nephritis compared to patients with inactive lupus or healthy controls. Objective of this study is to assess the specificity of urinary PF4 for lupus nephritis (LN). PF4 is a small cytokine, also known as CXCL-4, known to play a role in inflammation. Methods Urinary PF4 level was measured using ELISA in urine samples obtained from 50 chronic kidney disease patient samples comprising of DN (Diabetic Nephropathy) (N = 23), HTN Nephropathy (Hypertensive nephropathy) (N = 6), combination of DN and HTN nephropathy (N = 4), IgA nephropathy (N = 4), FSGS (Focal segmental glomerular sclerosis) (N = 13). As a negative control, urine samples were included from healthy controls, while urine samples from patients with active lupus nephritis were included as a positive control. All results were normalized to urinary creatinine. The urinary PF4 levels in various CKD groups were compared to both negative and positive controls. Results Urinary PF4 was significantly elevated (P<0.05) in samples from DN (678±285 pg/mg), FSGS (423±208 pg/mg), and LN (1438±901 pg/mg), compared to healthy controls (11±10 pg/mg). Urine PF4 levels in IgA nephropathy (24±15 pg/mg), HTN nephropathy (38±33), and DN/HTN nephropathy (463±410 pg/mg) were not significantly elevated compared to healthy controls. Conclusion PF4, as a urinary biomarker, exhibited significant elevation in patients with DN, FSGS as well as LN when compared to other renal diseases like IgA nephropathy and HTN nephropathy. Hence PF4 may aid in the noninvasive monitoring of DN, FSGS, and LN.