MO371: Should We Systematically Look for Urine Alterations in all Patients With Monoclonal Gammopathy of Undetermined Significance?

Abstract BACKGROUND AND AIMS Monoclonal gammopathy of undetermined significance (MGUS) has a high prevalence in the elderly population, being as high as 9% in subjects over 85 years. Population aging leads to an increase in the number of patients with MGUS. In 2012, monoclonal gammopathy of renal significance (MGRS) was described to identify MGUS patients with renal alterations but without overt hematological disorders. Despite an increasing number of cases and case series being reported, the prevalence and natural history of MGRS are not known with precision, in part because a systematic search for kidney damage is not standardized in all patients in whom MGUS is diagnosed. Our objective was to analyze in how many MGUS patients urine has been systematically analyzed and in how many of them any alterations suggestive of MGRS were detected. METHOD A retrospective observational study was carried out in our center of all patients in whom a paraprotein had been detected in the blood during the first trimester of 2018 and who did not present a known underlying hematological disorder. Glomerular filtration rate (GFR) was estimated using the CKD-EPI equation. The percentage of patients with a urine test using dipstick and urine sediment was analyzed, as well as the presence or any alteration suggestive of MGRS in them. RESULTS Three hundred and sixty patients were recorded, 44% females and with a mean age of 74 ± 12 years. Mean GFR was 69 ± 22 mL/min/1.73 m2 being 32% below 60 mL/min/1.73 m2. Urine dipstick and urine sediment were performed in only 42% and 24% of patients, respectively. Urine dipstick was more frequently performed in patients with worse GFR (72 ± 20 versus 64 ± 24 mL/min/1.73 m2P = 0.001) and in older patients (73 ± 13 versus 76 ± 11, P = 0.027). Similarly, urine sediment was more frequently performed in patients with worse GFR (72 ± 20 versus 59 ± 25 mL/min/1.73 m2 P < 0.001). Significant hemoglobinuria was found in 38% and dipstick albuminuria in 29% of them. Among those patients with urine sediment analysis, significant hematuria was detected in 56% and leukocyturia in 52%. Patients with significant dipstick hemoglobinuria (70 ± 21 versus 55 ± 26 mL/min/1.73 m2 P < 0.001) and albuminuria (68 ± 21 versus 54 ± 28 mL/min/1.73 m2 P = 0.005) showed worse GFR (figure 1). CONCLUSION Despite the risk of suffering some pathologic renal conditions included in the term MGRS, in most of our patients with MGUS, a urine dipstick or sediment analysis is not performed. MGUS patients with urine alterations show worse renal function. We advocate that all MGUS patients should have a dipstick and sediment urinalysis to rule out any possible associated kidney damage.