From the Guidelines
Yes, the albumin-to-creatinine ratio (ACR) can be elevated in urinary tract infections (UTIs). According to the most recent guideline evidence from 2024 1, infection is listed as a factor that can cause an increase in albumin and protein in the urine, leading to a falsely elevated ACR or protein-to-creatinine ratio (PCR). This is due to the production of protein from the organism during a symptomatic urinary infection.
Key Points to Consider
- The elevation in ACR during a UTI is typically temporary and resolves once the infection is effectively treated with antibiotics, such as nitrofurantoin, trimethoprim-sulfamethoxazole, or ciprofloxacin, depending on bacterial sensitivity patterns.
- It is essential to repeat ACR testing after the UTI has resolved to determine if the elevated levels were solely due to the infection or if there might be underlying kidney disease.
- The mechanism behind this elevation involves inflammatory cytokines and oxidative stress during infection that temporarily alter kidney filtration properties.
- For accurate assessment of kidney function, ACR testing should be performed when there is no active urinary tract infection, as recommended by the 2024 KDIGO clinical practice guideline for the evaluation and management of chronic kidney disease 1.
Clinical Implications
- Clinicians should be aware of the factors that can affect the interpretation of ACR measurements, including UTIs, to promote appropriate interpretation of proteinuria data.
- Understanding these factors is crucial for making informed decisions about patient care and for avoiding misinterpretation of ACR results that could lead to unnecessary further testing or inappropriate management.
From the Research
Elevated ACR in UTI
- ACR (Acute Phase Reactant) can be elevated in Urinary Tract Infections (UTIs), particularly in upper UTIs such as acute pyelonephritis 2.
- The study found that CRP (C-reactive protein) levels were significantly higher in patients with upper UTI compared to those with lower UTI, with 34 patients having CRP levels >100 mg/L, all of whom had upper UTI 2.
- However, other studies focused on the diagnosis and management of UTIs, including acute uncomplicated UTIs in adults 3, 4, and the use of antimicrobials for UTI treatment 5, 4, but did not specifically address the elevation of ACR in UTI.
- A recent study on the treatment of pyelonephritis and complicated UTIs found that short-term antibiotic treatment was as effective as long-term treatment, but did not discuss ACR levels 6.
UTI Diagnosis and Management
- The diagnosis of UTI can be made based on symptoms, urine analysis, and culture, with antibiotic treatment guided by susceptibility testing 3, 4.
- First-line antibiotics for uncomplicated UTIs include nitrofurantoin, trimethoprim-sulfamethoxazole, and fosfomycin, with treatment durations varying from 3 to 7 days 3, 4.
- For complicated UTIs, such as pyelonephritis, treatment may involve longer courses of antibiotics, but a recent study found that short-term treatment may be as effective as long-term treatment 6.
Biomarkers for UTI
- CRP levels have been shown to be a useful biomarker for distinguishing between upper and lower UTIs, with higher levels indicating upper UTI 2.
- However, the use of ACR as a biomarker for UTI is not well established, and further research is needed to determine its utility in this context.