Does urinary tract infection cause proteinuria or microalbuminuria? A systematic review

Extract

Introduction

Proteinuria, the presence of increased quantities of protein in the urine [ 1 , 2 ] can be detected by a variety of methods [ 3 ] including reagent-strip tests (e.g. Albustix™), which can be used in a point-of-care testing environment, and chemical tests available in the laboratory. Highly specific immunoassays for specific proteins including albumin are also used. Screening for proteinuria has diagnostic value in the initial detection and confirmation of proteinuric renal disease. Proteinuria is also an important predictor of progressive kidney damage [ 4 ] and a potent independent cardiovascular risk marker and predictor [ 5 ]. Among patients with suspected or proven chronic kidney disease (CKD), including diabetic nephropathy, reflux nephropathy and early glomerulonephritis, urinalysis for proteinuria is accepted as a useful way of identifying patients at risk of progressive kidney disease. Urinalysis for proteinuria is recommended as part of the initial assessment of patients with hypertension [ 6–8 ]. In people with diabetes mellitus the identification of increased urinary albumin excretion allows the diagnosis of diabetic nephropathy. Microalbuminuria also serves as a risk marker for progressive kidney disease and increased cardiovascular risk [ 9 ], even among non-diabetic individuals [ 10–13 ]. Urinary tract infections (UTIs) are commonly said to be associated with positive results in reagent-strip urinalysis for proteinuria, with some reviews suggesting between 63 and 83% of cases of culture-confirmed UTI having reagent-strip positive tests for protein [ 14 ]. Symptomatic UTIs account for 2–3% of all consultations in general practice and around 6% in the case of women. Asymptomatic UTI is found in approximately 4–7% of pregnant women, 10% of elderly men and 20% of elderly women. Uropathogenic strains of Escherichia coli account for the majority of UTIs that occur in the community [ 15 , 16 ].