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Luzardo ML. Effects of higher dietary acid load: a narrative review with special emphasis in children. Pediatr Nephrol 2024:10.1007/s00467-024-06466-7. [PMID: 39093454 DOI: 10.1007/s00467-024-06466-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/10/2024] [Revised: 07/05/2024] [Accepted: 07/08/2024] [Indexed: 08/04/2024]
Abstract
Metabolic effects of high diet acid load (DAL) have been studied for years in adults, although only recently in children. Contemporary diets, especially those of Western societies, owe their acidogenic effect to high animal-origin protein content and low contribution of base-forming elements, such as fruits and vegetables. This imbalance, where dietary acid precursors exceed the body's buffering capacity, results in an acid-retaining state known by terms such as "eubicarbonatemic metabolic acidosis," "low-grade metabolic acidosis," "subclinical acidosis," or "acid stress". Its consequences have been linked to chronic systemic inflammation, contributing to various noncommunicable diseases traditionally considered more common in adulthood, but now have been recognized to originate at much earlier ages. In children, effects of high DAL are not limited to growth impairment caused by alterations of bone and muscle metabolism, but also represent a risk factor for conditions such as obesity, insulin resistance, diabetes, hypertension, urolithiasis, and chronic kidney disease (CKD). The possibility that high DAL may be a cause of chronic acid-retaining states in children with growth impairment should alert pediatricians and pediatric nephrologists, since its causes have been attributed traditionally to inborn errors of metabolism and renal pathologies such as CKD and renal tubular acidosis. The interplay between DAL, overall diet quality, and its cascading effects on children's health necessitates comprehensive nutritional assessments and interventions. This narrative review explores the clinical relevance of diet-induced acid retention in children and highlights the potential for prevention through dietary modifications, particularly by increasing fruit and vegetable intake alongside appropriate protein consumption.
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Wieërs MLAJ, Beynon-Cobb B, Visser WJ, Attaye I. Dietary acid load in health and disease. Pflugers Arch 2024; 476:427-443. [PMID: 38282081 PMCID: PMC11006742 DOI: 10.1007/s00424-024-02910-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2023] [Revised: 01/07/2024] [Accepted: 01/09/2024] [Indexed: 01/30/2024]
Abstract
Maintaining an appropriate acid-base equilibrium is crucial for human health. A primary influencer of this equilibrium is diet, as foods are metabolized into non-volatile acids or bases. Dietary acid load (DAL) is a measure of the acid load derived from diet, taking into account both the potential renal acid load (PRAL) from food components like protein, potassium, phosphorus, calcium, and magnesium, and the organic acids from foods, which are metabolized to bicarbonate and thus have an alkalinizing effect. Current Western diets are characterized by a high DAL, due to large amounts of animal protein and processed foods. A chronic low-grade metabolic acidosis can occur following a Western diet and is associated with increased morbidity and mortality. Nutritional advice focusing on DAL, rather than macronutrients, is gaining rapid attention as it provides a more holistic approach to managing health. However, current evidence for the role of DAL is mainly associative, and underlying mechanisms are poorly understood. This review focusses on the role of DAL in multiple conditions such as obesity, cardiovascular health, impaired kidney function, and cancer.
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Affiliation(s)
- Michiel L A J Wieërs
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus MC, University Medical Center, Rotterdam, The Netherlands
| | - Beverley Beynon-Cobb
- Department of Nutrition & Dietetics, University Hospitals Coventry & Warwickshire NHS Trust, Coventry, UK
- Department of Twin Research and Genetic Epidemiology, King's College London, London, UK
| | - Wesley J Visser
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus MC, University Medical Center, Rotterdam, The Netherlands
- Department of Internal Medicine, Division of Dietetics, Erasmus MC, University Medical Center, Rotterdam, The Netherlands
| | - Ilias Attaye
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus MC, University Medical Center, Rotterdam, The Netherlands.
- Department of Twin Research and Genetic Epidemiology, King's College London, London, UK.
- Amsterdam Cardiovascular Sciences, Diabetes & Metabolism, Amsterdam, The Netherlands.
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Berman AR, Specht AJ, Castro RA, Cooke KL, Gilor S, Harris AN. Correlation between urine anion gap and urine ammonia-creatinine ratio in healthy cats and cats with kidney disease. J Vet Intern Med 2024; 38:1068-1073. [PMID: 38348890 PMCID: PMC10937481 DOI: 10.1111/jvim.17002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Accepted: 01/22/2024] [Indexed: 03/16/2024] Open
Abstract
BACKGROUND Ammonium excretion decreases as kidney function decreases in several species, including cats, and may have predictive or prognostic value in patients with chronic kidney disease (CKD). Urine ammonia measurement is not readily available in clinical practice, and urine anion gap (UAG) has been proposed as a surrogate test. OBJECTIVES Evaluate the correlation between urine ammonia-to-creatinine ratio (UACR) and UAG in healthy cats and those with CKD and determine if a significant difference exists between UAG of healthy cats and cats with CKD. ANIMALS Urine samples collected from healthy client-owned cats (n = 59) and those with stable CKD (n = 17). METHODS Urine electrolyte concentrations were measured using a commercial chemistry analyzer and UAG was calculated as ([sodium] + [potassium]) - [chloride]. Urine ammonia and creatinine concentrations had been measured previously using commercially available enzymatic assays and used to calculate UACR. Spearman's rank correlation coefficient between UAG and UACR was calculated for both groups. The UAG values of healthy cats and cats with CKD were assessed using the Mann-Whitney test (P < .05). RESULTS The UAG was inversely correlated with UACR in healthy cats (P < .002, r0 = -0.40) but not in cats with CKD (P = .55; r0 = -0.15). A significant difference was found between UAG in healthy cats and those with CKD (P < .001). CONCLUSIONS AND CLINICAL IMPORTANCE The UAG calculation cannot be used as a substitute for UACR in cats. The clinical relevance of UAG differences between healthy cats and those with CKD remains unknown.
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Affiliation(s)
- Alyssa R. Berman
- Department of Small Animal Clinical ScienceUniversity of Florida College of Veterinary MedicineGainesvilleFloridaUSA
| | - Andrew J. Specht
- Department of Small Animal Clinical ScienceUniversity of Florida College of Veterinary MedicineGainesvilleFloridaUSA
| | - Rebeca A. Castro
- Department of Small Animal Clinical ScienceUniversity of Florida College of Veterinary MedicineGainesvilleFloridaUSA
| | - Kirsten L. Cooke
- Department of Small Animal Clinical ScienceUniversity of Florida College of Veterinary MedicineGainesvilleFloridaUSA
| | - Shir Gilor
- Department of Comparative, Diagnostics and Population MedicineUniversity of Florida College of Veterinary MedicineGainesvilleFloridaUSA
| | - Autumn N. Harris
- Department of Small Animal Clinical ScienceUniversity of Florida College of Veterinary MedicineGainesvilleFloridaUSA
- Division of Nephrology, Hypertension and Renal TransplantationUniversity of Florida College of MedicineGainesvilleFloridaUSA
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Zaki SA, Shanbag P. Metabolic Acidosis in Children: A Literature Review. EUROPEAN MEDICAL JOURNAL 2023. [DOI: 10.33590/emj/10302459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/12/2023] Open
Abstract
Metabolic acidosis is characterised by a primary decrease in the serum bicarbonate concentration, a secondary decrease in the arterial partial pressure of CO2, and a reduction in blood pH. Metabolic acidosis, acute or chronic, may have deleterious effects on cellular function and cause increased morbidity and mortality. A systematic review of the available literature was performed to identify data on the prevalence, manifestations, cause, outcomes, and treatment of metabolic acidosis in children. Online databases (Ovid Medline, Embase, and PubMed), commercial search engines (including Google), and chapters on metabolic acidosis in the standard textbooks of paediatrics and medicine were reviewed.
Systematic approach to acute metabolic acidosis starts with proper history taking and examination. This is followed by assessment of acid-base parameters, including pH, partial pressure of CO2, and bicarbonate concentration in arterial blood. Blood gas is needed to differentiate primary metabolic acidosis from compensated respiratory alkalosis. Once the diagnosis of a metabolic acidosis has been confirmed, serum electrolyte values are used to determine the serum anion gap. The various causes of increased and normal anion gap metabolic acidosis have been discussed in the article. The main aim of treatment in metabolic acidosis is to reverse the primary pathophysiology. In acute metabolic acidosis, sodium bicarbonate therapy is not beneficial due to potential complications and is reserved for specific situations. Base therapy is used in chronic metabolic acidosis where it ameliorates many of its untoward effects. Other modalities of treatment of metabolic acidosis include peritoneal or haemodialysis and tris-hydroxymethyl aminomethane.
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Affiliation(s)
- Syed Ahmed Zaki
- Department of Pediatrics, All India Institute of Medical Sciences, Hyderabad, India
| | - Preeti Shanbag
- Sir Jamshedjee Jeejeebhoy Group of Hospital and Grant Medical College, Mumbai, India
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Rehman MZ, Melamed M, Harris A, Shankar M, Rosa RM, Batlle D. Urinary Ammonium in Clinical Medicine: Direct Measurement and the Urine Anion Gap as a Surrogate Marker During Metabolic Acidosis. ADVANCES IN KIDNEY DISEASE AND HEALTH 2023; 30:197-206. [PMID: 36868734 DOI: 10.1053/j.akdh.2022.12.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Accepted: 12/15/2022] [Indexed: 03/05/2023]
Abstract
Ammonium is the most important component of urinary acid excretion, normally accounting for about two-third of net acid excretion. In this article, we discuss urine ammonium not only in the evaluation of metabolic acidosis but also in other clinical conditions such as chronic kidney disease. Different methods to measure urine NH4+ that have been employed over the years are discussed. The enzymatic method used by clinical laboratories in the United States to measure plasma ammonia via the glutamate dehydrogenase can be used for urine ammonium. The urine anion gap calculation can be used as a rough marker of urine ammonium in the initial bedside evaluation of metabolic acidosis such as in distal renal tubular acidosis. Urine ammonium measurements, however, should be made more available in clinical medicine for a precise evaluation of this important component of urinary acid excretion.
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Affiliation(s)
- Mohammed Z Rehman
- Division of Nephrology and Hypertension, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - Michal Melamed
- Department of Medicine (Nephrology), Albert Einstein College of Medicine/Montefiore Medical Center, Bronx, NY
| | - Autumn Harris
- Department of Small Animal Clinical Sciences College of Veterinary Medicine, Gainesville, FL
| | - Mythri Shankar
- Department of Nephrology, Institute of Nephro-urology, Bengaluru, India
| | - Robert M Rosa
- Division of Nephrology and Hypertension, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - Daniel Batlle
- Division of Nephrology and Hypertension, Northwestern University Feinberg School of Medicine, Chicago, IL.
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Uribarri J, Goldfarb DS, Raphael KL, Rein JL, Asplin JR. Beyond the Urine Anion Gap: In Support of the Direct Measurement of Urinary Ammonium. Am J Kidney Dis 2022; 80:667-676. [PMID: 35810828 DOI: 10.1053/j.ajkd.2022.05.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Accepted: 05/10/2022] [Indexed: 02/02/2023]
Abstract
Ammonium is a major urinary buffer that is necessary for the normal excretion of the daily acid load. Its urinary rate of excretion (UNH4) may be increased several fold in the presence of extrarenal metabolic acidosis. Therefore, measurement of UNH4 can provide important clues about causes of metabolic acidosis. Because UNH4 is not commonly measured in clinical laboratories, the urinary anion gap (UAG) was proposed as its surrogate about 4 decades ago, and it is still frequently used for that purpose. Several published studies strongly suggest that UAG is not a good index of UNH4 and support the concept that direct measurement of UNH4 is an important parameter to define in clinical nephrology. Low UNH4 levels have recently been found to be associated with a higher risk of metabolic acidosis, loss of kidney function, and death in persons with chronic kidney disease, while surrogates like the UAG do not recapitulate this risk. In order to advance the field it is necessary for the medical community to become more familiar with UNH4 levels in a variety of clinical settings. Herein, we review the literature, searching for available data on UNH4 under normal and various pathological conditions, in an attempt to establish reference values to interpret UNH4 results if and when UNH4 measurements become available as a routine clinical test. In addition, we present original data in 2 large populations that provide further evidence that the UAG is not a good predictor of UNH4. Measurement of urine NH4 holds promise to aid clinicians in the care of patients, and we encourage further research to determine its best diagnostic usage.
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Affiliation(s)
- Jaime Uribarri
- Renal Division, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York.
| | | | - Kalani L Raphael
- Oregon Health & Science University and VA Portland Health Care System, Portland, Oregon
| | - Joshua L Rein
- Renal Division, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - John R Asplin
- Litholink Corporation, Laboratory Corporation of America Holdings, Chicago, Illinois
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Ravikumar NPG, Pao AC, Raphael KL. Acid-Mediated Kidney Injury Across the Spectrum of Metabolic Acidosis. Adv Chronic Kidney Dis 2022; 29:406-415. [PMID: 36175078 DOI: 10.1053/j.ackd.2022.04.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Revised: 04/15/2022] [Accepted: 04/25/2022] [Indexed: 01/25/2023]
Abstract
Metabolic acidosis affects about 15% of patients with chronic kidney disease. As kidney function declines, the kidneys progressively fail to eliminate acid, primarily reflected by a decrease in ammonium and titratable acid excretion. Several studies have shown that the net acid load remains unchanged in patients with reduced kidney function; the ensuing acid accumulation can precede overt metabolic acidosis, and thus, indicators of urinary acid or potential base excretion, such as ammonium and citrate, may serve as early signals of impending metabolic acidosis. Acid retention, with or without overt metabolic acidosis, initiates compensatory responses that can promote tubulointerstitial fibrosis via intrarenal complement activation and upregulation of endothelin-1, angiotensin II, and aldosterone pathways. The net effect is a cycle between acid accumulation and kidney injury. Results from small- to medium-sized interventional trials suggest that interrupting this cycle through base administration can prevent further kidney injury. While these findings inform current clinical practice guidelines, large-scale clinical trials are still necessary to prove that base therapy can limit chronic kidney disease progression or associated adverse events.
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Affiliation(s)
- Naveen P G Ravikumar
- Division of Nephrology & Hypertension, Department of Medicine, Oregon Health & Science University, Portland, OR; Veterans Affairs Portland Health Care System, Portland, OR
| | - Alan C Pao
- Division of Nephrology, Department of Medicine, Stanford University School of Medicine, Stanford, CA; Veterans Affairs Palo Alto Health Care System, Palo Alto, CA
| | - Kalani L Raphael
- Division of Nephrology & Hypertension, Department of Medicine, Oregon Health & Science University, Portland, OR; Veterans Affairs Portland Health Care System, Portland, OR.
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Nagami GT, Kraut JA. Regulation of Acid-Base Balance in Patients With Chronic Kidney Disease. Adv Chronic Kidney Dis 2022; 29:337-342. [PMID: 36175071 DOI: 10.1053/j.ackd.2022.05.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Revised: 05/16/2022] [Accepted: 05/31/2022] [Indexed: 01/25/2023]
Abstract
Normallly the kidneys handle the daily acid load arising from net endogenous acid production from the metabolism of ingested animal protein (acid) and vegetables (base). With chronic kidney disease, reduced acid excretion by the kidneys is primarily due to reduced ammonium excretion such that when acid excertion falls below acid porduction, acid accumulation occurs. With even mild reductions in glomerular filtration rate (60 to 90 ml/min), net acid excretion may fall below net acid production resulting in acid retention which may be initially sequestered in interstitial compartments in the kidneys, bones, and muscles resulting in no fall in measured systemic bicarbonate levels (eubicarbonatemic metabolic acidosis). With greater reductions in kidney function, the greater quantities of acid retained spillover systemically resulting in low pH (overt metabolic acidosis). The evaluation of acid-base balance in patients with CKD is complicated by the heterogeneity of clinical acid-base disorders and by the eubicarbonatemic nature of the early phase of acid retention. If supported by more extensive studies, blood gas analyses to confirm the acid-base disorder and newer ways for assessing the presence of acidosis such as urinary citrate measurements may become routine tools to evaluate and treat acid-base disorders in individuals with CKD.
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Affiliation(s)
- Glenn T Nagami
- Division of Nephrology, Department of Medicine, VA Greater Los Angeles Healthcare System, Los Angeles, CA; David Geffen School of Medicine, UCLA, Los Angeles, CA.
| | - Jeffrey A Kraut
- Division of Nephrology, VHAGLA Healthcare System, Los Angeles, CA; UCLA Membrane Biology Laboratory, David Geffen UCLA School of Medicine, Los Angeles, CA
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Agrawal N, Mahata R, Chakraborty PP, Basu K. Secondary distal renal tubular acidosis and sclerotic metabolic bone disease in seronegative spondyloarthropathy. BMJ Case Rep 2022; 15:e248712. [PMID: 35292549 PMCID: PMC8928265 DOI: 10.1136/bcr-2021-248712] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/25/2022] [Indexed: 11/03/2022] Open
Abstract
Adults with distal renal tubular acidosis (dRTA) commonly present with hypokalaemia (with/without paralysis), nephrolithiasis/nephrocalcinosis and vague musculoskeletal symptoms. All adults with dRTA should be thoroughly evaluated for systemic diseases, certain medications and toxins. The leading cause of acquired or secondary dRTA in adults is primary Sjögren syndrome (SS); however, other collagen vascular diseases (CVDs) including seronegative spondyloarthropathy (SSpA) may at times give rise to secondary dRTA. Metabolic bone disease is often encountered in adults with dRTA, and the list includes osteomalacia and secondary osteoporosis; sclerotic metabolic bone disease is an extremely rare manifestation of dRTA. Coexistence of dRTA and sclerotic bone disease is seen in primary dRTA due to mutation in CA2 gene and acquired dRTA secondary to systemic fluorosis. Primary SS and SSpA, rarely if ever, may also lead to both secondary dRTA and osteosclerosis. Circulating autoantibodies against carbonic anhydrase II and possibly calcium sensing receptor may explain both these features in patients with CVD.
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Affiliation(s)
- Neeti Agrawal
- Endocrinology & Metabolism, Medical College and Hospital Kolkata, Kolkata, West Bengal, India
| | - Rahin Mahata
- Endocrinology & Metabolism, Medical College and Hospital Kolkata, Kolkata, West Bengal, India
| | | | - Kaushik Basu
- General Medicine & Rheumatology, Medical College and Hospital Kolkata, Kolkata, West Bengal, India
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Abstract
PURPOSE OF REVIEW Evaluation of the kidney stone patient includes measurement of 24 h urine chemistries. This review summarizes the application of physiologic principles to the interpretation of urine chemistries, using sulfate and ammonium to estimate diet acid load, and the renal response. RECENT FINDINGS There has been increased recognition of the need to measure urine ammonium excretion in the clinical setting in order to understand renal acid excretion. Some 24 h urine kidney stone panels include ammonium measurements, providing an opportunity to apply this measurement to clinical practice. In order to better interpret ammonium excretion, one needs an estimate of dietary acid load to understand the driving forces for ammonium excretion. Sulfate is also included in some kidney stone panels and functions as an estimate of diet acid load. Combining these analytes with urine pH, the clinician can quickly estimate dietary stone risk as well as potential bowel disease, acidification disorders, and the presence of urease producing bacteria; all of which can affect stone risk. SUMMARY Measurement of ammonium and sulfate excretion along with urine pH provide important insights into the acid/alkali content of diet, presence and severity of bowel disease, presence of renal acidification disorders, and urinary infection.
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Affiliation(s)
- John R Asplin
- Litholink Corporation, Laboratory Corporation of America Holdings, Chicago, Illinois, USA
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Gruzdys V, Cahoon K, Pearson L, Raphael KL. Measurement of Urinary Ammonium Using a Commercially Available Plasma Ammonium Assay. KIDNEY360 2022; 3:926-932. [PMID: 36128493 PMCID: PMC9438425 DOI: 10.34067/kid.0000262022] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Accepted: 02/09/2022] [Indexed: 01/10/2023]
Abstract
Background Determination of urinary ammonium excretion is helpful in evaluating patients with acid-base disorders, chronic kidney disease, and nephrolithiasis. However, urinary ammonium levels are only measured by specialized laboratories in the United States, limiting widespread implementation. We evaluated the performance of a plasma ammonium assay to quantify urinary ammonium excretion and also determined ammonium stability under a variety of conditions. Methods An enzymatic plasma ammonium assay (Randox) was modified to measure urinary ammonium concentration. Urine samples were diluted 40-fold and then assayed on an Abbott Architect ci8200 analyzer. Assay precision, limit of quantitation, and linearity were determined. The method was compared against the formalin titration method, and stability studies were conducted at different temperatures and pH. Results After dilution, the assay had total precision of 18% at 2.54 mmol/L, 5% at 15.58 mmol/L, and 2% at 29.49 mmol/L, with a limit of quantitation of 2.92 mmol/L. Assay performance was linear in the range of 0.7-45 mmol/L. Method comparison against the formalin method showed a slope of 0.98 and intercept of -0.37 mmol/L. Urinary ammonium was determined to be stable for 48 hours at room temperature and for 9 days at 4°C and -20°C at pH 5.6-6.3. Ammonium was less stable at pH 3.8 and 8.5. When stored at -80°C, urinary ammonium was stable for at least 24 months. Conclusions The modified enzymatic plasma ammonium assay reliably quantifies urine ammonium at physiologic concentrations. It compares well with the formalin titration method and is suitable for routine clinical use on an automated chemistry analyzer.
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Affiliation(s)
| | | | - Lauren Pearson
- Department of Pathology, University of Utah School of Medicine, Health Sciences Center, Salt Lake City, Utah
| | - Kalani L. Raphael
- Division of Nephrology and Hypertension, Department of Medicine, Oregon Health and Science University and VA Portland Health Care System, Portland, Oregon
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Díaz-Anadón L, Cardo L, Santos F, Gil-Peña H. Evaluation of urinary acidification in children: Clinical utility. Front Pediatr 2022; 10:1051481. [PMID: 36389372 PMCID: PMC9660234 DOI: 10.3389/fped.2022.1051481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Accepted: 10/10/2022] [Indexed: 11/13/2022] Open
Abstract
The kidney plays a fundamental role in acid-base homeostasis by reabsorbing the filtered bicarbonate and by generating new bicarbonate, to replace that consumed in the buffering of non-volatile acids, a process that leads to the acidification of urine and the excretion of ammonium (NH4 +). Therefore, urine pH (UpH) and urinary NH4 + (UNH4 +) are valuable parameters to assess urinary acidification. The adaptation of automated plasma NH4 + quantification methods to measure UNH4 + has proven to be an accurate and feasible technique, with diverse potential indications in clinical practice. Recently, reference values for spot urine NH4 +/creatinine ratio in children have been published. UpH and UNH4 +, aside from their classical application in the study of metabolic acidosis, have shown to be useful in the identification of incomplete distal renal tubular acidosis (dRTA), an acidification disorder, without overt metabolic acidosis, extensively described in adults, and barely known in children, in whom it has been found to be associated to hypocitraturia, congenital kidney abnormalities and growth impairment. In addition, a low UNH4 + in chronic kidney disease (CKD) is a risk factor for glomerular filtration decay and mortality in adults, even in the absence of overt metabolic acidosis. We here emphasize on the need of measuring UpH and UNH4 + in pediatric population, establishing reference values, as well as exploring their application in metabolic acidosis, CKD and disorders associated with incomplete dRTA, including growth retardation of unknown cause.
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Affiliation(s)
- Lucas Díaz-Anadón
- Division of Pediatric Nephrology, Department of Pediatrics, Hospital Universitario Central de Asturias, Oviedo, Asturias, Spain.,Department of Medicine, Faculty of Medicine, University of Oviedo, Oviedo, Asturias, Spain
| | - Leire Cardo
- Clinical Biochemistry Department, Laboratory of Medicine, Hospital Universitario Central de Asturias, Oviedo, Asturias, Spain
| | - Fernando Santos
- Department of Medicine, Faculty of Medicine, University of Oviedo, Oviedo, Asturias, Spain
| | - Helena Gil-Peña
- Division of Pediatric Nephrology, Department of Pediatrics, Hospital Universitario Central de Asturias, Oviedo, Asturias, Spain.,Department of Medicine, Faculty of Medicine, University of Oviedo, Oviedo, Asturias, Spain.,Section of Pediatrics, Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), Oviedo, Asturias, Spain
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The Implication of Dropping Race from the MDRD Equation to Estimate GFR in an African American-Only Cohort. Int J Nephrol 2021; 2021:1880499. [PMID: 34824870 PMCID: PMC8610663 DOI: 10.1155/2021/1880499] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 06/02/2021] [Accepted: 10/28/2021] [Indexed: 01/13/2023] Open
Abstract
The widely used Modification of Diet in Renal Disease (MDRD) formula adapts a 1.212 multiplier for individuals who are identified as African Americans (AAs) or Blacks, which leads to a higher GFR estimation. As it stands, AAs have a lower prevalence of chronic kidney disease (CKD) but higher incidence of end-stage renal disease (ESRD) compared with Whites. Many hypotheses have been postulated to explain this paradox, but the imprecision of the GFR estimation with race-adaptation could be contributory. We performed a single-center, longitudinal, retrospective study on a cohort of outpatient AA patients using the MDRD and MDRDrace removed and CKD-EPI and CKD-EPIrace removed and their progression to CKD G5 (eGFR <15 ml/min/1.73 m2). 327 patients were analyzed. Median follow-up was 88.1 months (interquartile range, 34.4–129.1). When race was removed from MDRD, 39.9% of patients in CKD G1/2 were reclassified to CKD G3a, 72.6% of patients in CKD G3a would be reclassified to CKD G3b, and 54.1% and 36.4% of patients would be reclassified from CKD 3b to CKD G4 and CKD G4 to CKD G5, respectively (p < 0.0001). Comparing the CKD-EPI formula against the MDRD in our cohort, we found that 8.2%, 18.8%, and 11.4% of patients were reclassified from CKD G1/2 to CKD G3a, CKD G3a to G3b, and CKD G3b to CKD G4 respectively. Overall median time to progression to CKD G5 was 137.4 (131.9–142.8) months in patients who were not reclassified and 133.6 (127.6–139.6) months for patients who were reclassified by MDRDrace removed(p < 0.288). Concerns of inequitable access to healthcare have elicited calls to review race-corrected eGFR equations. A substantial number of individuals would have their CKD stage reclassified should have the MDRDrace removed equation be adopted en masse on an AA-only population. The discrepancy is highest at the 45–59 and >60 ml/min/1.72 min2 ranges. This will have tremendous impact on our center's approach to pharmacological dosing, referral system, best practices, and outcome surveillance. Comprehensive review of the current “race-corrected” eGFR will require a multifaceted approach and adjunctive use of noncreatinine-based approach.
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