The Association of Recurrent Urinary Tract Infections and Matrix Metalloproteinase 7 Levels as Predictors of Lupus Nephritis Flares in Systemic Lupus Erythematosus

Background: Systemic lupus erythematosus (SLE) is an autoimmune multisystemic disorder characterized by chronic inflammatory response. SLE frequently manifests as urinary tract disease. The most characteristic is renal involvement and consequently secondary lupus nephritis.
Objectives: To assess the possible impact of urinary matrix metalloproteinase 7 (MMP7) as an early predictor of lupus nephritis (LN) flares in SLE also to detect urinary tract infections (UTIs) and most common organisms in LN flares in SLE cases, and to associate between recurrent urinary tract infections and matrix metalloproteinase 7 levels in SLE cases.
Subjects and methods: This case-control study was subjected to 180 participants, Group I (SLE group): included 60 cases with SLE without nephritis. Group II (LN group): included 60 patients with LN. Group III (control group): included 60 normal participants. All cases were subjected to clinical examination and laboratory tests including CBC, urine analysis, Kidney function tests, 24-hour proteinuria, C3, C4, ANA, and Anti-DNA antibodies. Urinary MMP7 level were detected by ELISA. Microbiological detection of bacterial urinary tract infections was done by conventional methods and VITEK system.
Results: Regarding the isolated microorganisms, there was remarkable variation between the strains and both urinary and serum MMP7 (p<0.001). At cut-off point (1.628 ng/ml) the capability of serum MMP7 to differentiate between SLE cases with LN and without LN was with 65% of sensitivity and 35% of specificity. At cut-off point (3.135 ng/ml) the ability of urinary MMP7 to differentiate between SLE cases with nephritis and without LN had (75%) sensitivity and (45%) specificity.
Conclusion: Both urinary and serum MMP7 have potential ability to predict lupus nephritis with distinction of urinary MMP7. Bacterial infection is a prevalent infection in SLE cases, and its diagnosis is critical for proper treatment of those individuals.