Usefulness of urinary fibronectin and laminin as biomarkers of glomerular injury in diabetics in Port Harcourt, Nigeria

About one-third of diabetes mellitus (DM) patients are complicated by diabetic nephropathy. It is even more challenging in type 2 DM in which this complication may occur before presentation. Microalbuminuria which is the traditional marker of early diabetic nephropathy is limited in its usefulness because it is detected when significant renal damage has already occurred. The aim of this study was to evaluate and compare urinary fibronectin and laminin with microalbuminuria as markers of glomerular injury in type 2 DM patients. A cross-sectional study with 120 consenting non-hypertensive type 2 DM, consisting of 57 (47.5%) males and 63 (52.5%) females; and 120 non-diabetic/non-hypertensive controls, consisting of 51 (42.5%) males and 69 (57.5%) females. Urinary albumin, fibronectin and laminin as well as plasma glucose were measured. The mean albumin –creatinine ratio was significantly higher (p<0.001) among type 2 DM (1.990.78 mg/mmol) compared to the control (0.120.01 mg/mmol). Also, urinary fibronectin (1.290.35 µg/mL) and laminin (1251.34+234.61 pg/mL) were significantly higher (p<0.001) in type 2 DM patients than in controls (0.290.07 µg/mL and 127.8114.07 pg/mL respectively). The sensitivity test for urinary fibronectin and laminin was 93.9% each while their specificities were 8.0 and 13.8% respectively. The negative predictive values (NPV) for urinary fibronectin and laminin were 77.8 and 85.7% respectively while the positive predictive values (PPV) were 27.9 and 29.2% respectively. This study suggests that assay for urinary fibronectin and laminin, which showed high sensitivities and high negative predictive values are useful as markers of early diabetic kidney disease and can substitute microalbuminuria in the routine evaluation of type 2 DM patients. The slightly higher PPV and NPV for urinary laminin suggest that it is a better marker than urinary fibronectin. Key words: Diabetes mellitus, microalbuminuria, urinary fibronectin, urinary laminin.