Background: Lupus nephritis (LN) is a form of glomerulonephritis and constitutes one of the most
severe organ manifestations of SLE. LN is histologically classified into six distinct classes that 
represent different manifestations and severities of renal involvement in SLE. Most patients with SLE 
who develop LN do so within 5 years of an SLE diagnosis, although it is not uncommon for LN to 
develop at later times. In many cases, LN is the presenting manifestation that results in the diagnosis 
of SLE. Urinary protein excretion in a 12-h or 24-h urine collection provides the best estimate of 
proteinuria. For practical reasons, urinary protein-to creatinine ratio in early morning or random 
daytime urine samples has replaced urinary protein excretion in 24-h urine collections in many 
centres, although this approach has not been carefully validated. Objectives: This work aims to 
evaluate the role of proteinuria in Diagnosis of Lupus Nephritis. Methods: The study was conducted 
on 60 cases of Systemic Lupus Erythmatosis, The age of patients ranged from 27.5 to 43 patients were 
subjected to routine and special investigations which included C.B.C (complete blood count) using
celltac G, Nihon KHODEN CORPORATION, AUTOMATED HEMATOLOGY ANALYZER,
japan). And renal functions including blood urea and serum creatinine using auto-analyzer 
SELECTRA, ELITech Group, clinical chemistry automation systems, Finland). Results: Patients with 
persistent proteinuria, such as protein excretion of more than 0.7–0.8 g daily 1 year after treatment 
initiation or kidney function deterioration despite adequate treatment (‘refractory LN') should be 
assessed for other possible causes, including potential nephrotoxic side effects of medications.
Conclusion: 24h urinary protein is considered corner stone in the Diagnosis of Lupus Nephritis Activity.