Simple And Cost-Effective Classics Are Back- Revisiting The Role Of Urine Microscopic Analysis For Assessing Severity Of Renal Involvement In Lupus Nephritis

Abstract

Casestudy Urinalysis is important to assess disease activity in Lupus nephritis (LN). Hematuria, pyuria, cellular/granular casts and proteinuria are scored separately for assessing renal activity in SLEDAI. However, pyuria is not specific, and could indicate infection. We studied the correlation of microscopic urinalysis and degree of lymphocyturia with histological ISN/RPS 2018 class of LN. Methods Pre-biopsy urine was collected in 76 LN patients. The urine sediment was analyzed using light and phase- contrast microscope. Smear stained with supravital stain Sternheimer Malbin, was assessed semi-quantitatively for lymphocytes (per HPF). Renal biopsy was classified into proliferative (Class III/IV ± V)[N=64] and non-proliferative LN (Class I, II, V, VI) [N=12]. Results 48 patients had active urinary sediment. Cellular and/or granular casts were identified only in proliferativeLN (n=15/64; 23.4%). Hematuria (Range 0-65/HPF) was seen in 45 patients. Dysmorphic RBCs were identified in proliferative (n=17/41; mean 9.9 RBCs/HPF) and were absent in non-proliferative LN (mean 1.4 RBCs/HPF). 20 of the 34 patients with pyuria showed predominant lymphocytes. Lymphocyturia (Range 0-20/HPF) was significantly higher in proliferative LN (Mean 4.6/HPF) as compared to non-proliferative LN (Mean 1.5/HPF). Degree of pyuria or proteinuria had no correlation with biopsy class or activity. Lymphocyturia and hematuria showed correlation with biopsy activity index (r=0.30 and 0.39; p<0.05 and <0.001 respectively). A cut-off of average 6 RBCs/HPF or 5 lymphocytes/HPF could correctly identify proliferative LN with 100% specificity (p<0.001; AUC 0.72 and 0.74 respectively, combined AUC 0.81) and sensitivity of 0.42 and 0.36 respectively. Conclusion Although renal biopsy is the gold standard for assessment of renal lesions in LN, urine lymphocytes ≥5 and RBCs ≥6/HPF have a high specificity to differentiate proliferative and non-proliferative LN. This may be especially important in patients having comorbidities contraindicating a renal biopsy. Defining urine sediments using lymphocytes can increase the specificity of clinical activity indices.