Uric acid reference values: report on 1750 healthy Brazilian children and adolescents.

BACKGROUND: Our purpose was to determine reference values and determinants of serum uric acid (SUA) in children and adolescents. METHODS: A fasting blood sample was collected from 1750 schoolchildren and adolescents (6-17 years). Puberty was defined according to the Tanner scale. Bodyweight, muscle mass, and body fat percentage were determined by bioimpedance. Data are given as cut-offs and mean ± standard deviation. RESULTS: SUA level was higher in children that had already entered puberty (4.2 ± 1.1 mg/dL) than among prepubescent (3.6 ± 0.8 mg/dL; p < 0.01). Considering the 90 percentile (p90) as the upper reference value, the following values are proposed for boys and girls, respectively: <10 years or prepubescent: ≤4.5 mg/dL and ≤4.8 mg/dL; from 10 to 13 years: ≤5.7 mg/dL and ≤5.2 mg/dL; from 14 to 17 years: ≤6.4 mg/dL and ≤5.3 mg/dL. Muscle mass explained part of the variability in SUA after pubescence, acting as an independent variable for higher levels of SUA. CONCLUSIONS: The sex, age, and phase of puberty influence SUA reference levels, and part of this influence could be explained by the higher muscle mass, mainly after the adolescence onset. IMPACT: The key message of this study is that high levels of uric acid in the blood are associated with metabolic syndrome and cardiovascular risk factors. These diseases should be prevented since the infancy However, it is necessary to establish reference values of uric acid (SUA) for children and adolescents. The Brazilian population is highly admixed and these values were not determined so far. We studied a robust sample of Brazilian schoolchildren and adolescents (6-17 years) and defined the 90th percentile of uric acid as the upper limit of normality for sex, age, and pubertal stage. These values can be used as a reference for other populations with similar characteristics.

The distributions of hematologic and biochemical values in healthy high-school adolescents in Japan.

Laboratory tests of adolescents are often interpreted by using reference intervals derived from adults, even though these populations differ in their physical and physiologic characteristics and disease susceptibility. Therefore, to examine the distribution of laboratory values specific for adolescents, we analyzed hematologic and biochemical measurements obtained from 12,023 healthy Japanese adolescents (ages 15 through 18 years; male, 9165; female, 2858) during 2009 through 2018. Distributions were shown as medians with 95% (2.5th and 97.5th percentiles) of values and were compared with those from previous studies that examined similar Asian populations. There were some differences between hematologic parameters, serum creatinine and uric acid concentration, and lipid levels of Japanese adults and adolescents. In comparison with other Asian populations, the distributions of serum uric acid and high-density-lipoprotein cholesterol in the present study were slightly higher than those in the other studies. Although further research is need, the distributions of hematologic and biochemical tests in adolescents may have the potential to facilitate the early identification and management of disease in this population.

Standardization of measurement procedures for serum uric acid: 8-year experience from Category 1 EQA program results in China.

Background Serum uric acid is a critical clinical indicator, and results without equivalence among laboratories cause troubles for disease diagnosis and patient management. External quality assessment (EQA) is a common tool for enhancing harmonization/standardization, therefore, the National Center for Clinical Laboratories in China has initiated a category 1 EQA for serum uric acid measurement since 2010 for evaluating its process of standardization. Methods Commutable EQA samples with target values assigned by reference measurement procedures were sent to participant laboratories. Both concentrations were measured 15 times in 3 days then means and intra-laboratory coefficient of variations (CVs) were reported. Biological variation criteria were used for analysis with CLIA88 criteria as a comparison. Results A total of 1250 laboratories participated in EQA programs from 2010 to 2017, pass rates calculated according to desirable specifications in biological variation database were on a rise overall and inter-laboratory mean bias and CVs were on a decrease. Homogeneous systems showed better inter-laboratory CVs and pass rates than heterogeneous systems. For the mostly used measurement systems; Abbott, Beckman, Roche Modular, Siemens and Hitachi showed desirable performances other than Roche Cobas, according to biological variation criteria. Conclusions Our study provides reliable information on the standardization of measurement procedures for serum uric acid for manufacturers and laboratories. Further improvements for standardization are still needed to make laboratories more patient-centered.

The EuBIVAS: Within- and Between-Subject Biological Variation Data for Electrolytes, Lipids, Urea, Uric Acid, Total Protein, Total Bilirubin, Direct Bilirubin, and Glucose.

BACKGROUND: The European Federation of Clinical Chemistry and Laboratory Medicine European Biological Variation Study (EuBIVAS) has been established to deliver rigorously determined data describing biological variation (BV) of clinically important measurands. Here, EuBIVAS-based BV estimates of serum electrolytes, lipids, urea, uric acid, total protein, total bilirubin, direct bilirubin, and glucose, as well as their associated analytical performance specifications (APSs), are presented. METHOD: Samples were drawn from 91 healthy individuals (38 male, 53 female; age range, 21-69 years) for 10 consecutive weeks at 6 European laboratories. Samples were stored at -80 °C before duplicate analysis of all samples on an ADVIA 2400 (Siemens Healthineers). Outlier and homogeneity analyses were performed, followed by CV-ANOVA on trend-corrected data, when relevant, to determine BV estimates with CIs. RESULTS: The within-subject BV (CVI) estimates of all measurands, except for urea and LDL cholesterol, were lower than estimates available in an online BV database, with differences being most pronounced for HDL cholesterol, glucose, and direct bilirubin. Significant differences in CVI for men and women/women <50 years of age were evident for uric acid, triglycerides, and urea. The CVA obtained for sodium and magnesium exceeded the EuBIVAS-based APS for imprecision. CONCLUSIONS: The EuBIVAS, which is fully compliant with the recently published Biological Variation Data Critical Appraisal Checklist, has produced well-characterized, high-quality BV estimates utilizing a stringent experimental protocol. These new reference data deliver revised and more exacting APS and reference change values for commonly used clinically important measurands, thus having direct relevance to diagnostics manufacturers, service providers, clinical users, and ultimately patients.

Absolute Quantification of Uric Acid in Human Urine Using Surface Enhanced Raman Scattering with the Standard Addition Method.

High levels of uric acid in urine and serum can be indicative of hypertension and the pregnancy related condition, preeclampsia. We have developed a simple, cost-effective, portable surface enhanced Raman scattering (SERS) approach for the routine analysis of uric acid at clinically relevant levels in urine patient samples. This approach, combined with the standard addition method (SAM), allows for the absolute quantification of uric acid directly in a complex matrix such as that from human urine. Results are highly comparable and in very good agreement with HPLC results, with an average <9% difference in predictions between the two analytical approaches across all samples analyzed, with SERS demonstrating a 60-fold reduction in acquisition time compared with HPLC. For the first time, clinical prepreeclampsia patient samples have been used for quantitative uric acid detection using a simple, rapid colloidal SERS approach without the need for complex data analysis.

Assessment of the trueness and inter-laboratory precision of routine uric acid assays using 4 frozen pooled serum samples measured by the Japan Society of Clinical Chemistry's HPLC method.

BACKGROUND: Reference procedures are required for evaluating the accuracy of routine analytical systems for uric acid (UA). External quality assessment (EQA) for UA has only been conducted with quality controls in China, and the results have not been published. This study was designed to investigate both the trueness and inter-laboratory precision of UA measurements among routine analytical systems using a candidate reference method. METHODS: We performed the HPLC method recommended by the Japan Society of Clinical Chemistry (JSCC). Next, we evaluated its analytical performance and validated its trueness. The performance of 4 routine analytical systems (5 instruments per system, n=20) for UA was assessed by using 4 frozen pooled serum samples measured by the HPLC method according to biologically relevant quality goals. RESULTS: Within-run, between-run, inter-day, and total CV of the method were less than 0.3%, 0.4%, 1.8%, and 2.6%, respectively. The UA measurements were consistent with the target values of standard reference material (SRM) 909b, the sixth ring trial for Reference Laboratories (RELA-2008) specimen, and national primary reference materials. The 4 frozen pooled serum samples were homogeneous, stable, and commutable. All routine systems achieved the desirable performance goal (total error <11.9%). CONCLUSIONS: We successfully reproduced the JSCC's HPLC method, which was simple, specific, precise, and accurate. We recommend this method as a reference method for UA measurement in human serum. Four routine analytical systems for UA measurement had acceptable traceability, and their UA results showed good concordance.

Nonenzymatic elimination of ascorbic acid in clinical samples.

OBJECTIVES: Ascorbic acid interferes significantly in the oxidative reaction of chromogenic reagents by peroxidase and hydrogen peroxide. Currently, ascorbate oxidase is commonly utilized for eliminating the interference of ascorbic acid in the oxidative colorimetric reaction. This enzyme, however, displays several disadvantages, such as high cost, variation from lot to lot, and low stability. We applied a series of commercially available and stable radicals (ascorbic acid quenchers [AAQs]) for nonenzymatic quenching of ascorbic acid in the uricase-based uric acid determination in serum and urine. DESIGN AND METHODS: In order to evaluate the quenching activity of AAQs, a commercially available uric acid detection kit was used. TBA-80FR.NEO biochemical analyzer was utilized for the assay. RESULTS: 4-Hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical (AAQ-2) was the most effective ascorbic acid quencher among the four stable radicals, and the uric acid assay suffered no interference by AAQ-2. The ascorbic acid quenching ability of 2 mmol/L of AAQ-2 in reagent solution (reagent-I) was > or = 2 U/ml ascorbate oxidase in reagent solution. CONCLUSIONS: AAQ-2 was proven to be a suitable quencher of ascorbic acid in clinical samples.

Relación entre acido urico serico y la eritrocitosis de altura / Relationship between uric acid and high altitude eritocitosis

Pregunta de investigción: Existe relación entre la cncentración de Acido Urico sérico y Eritrocitosis de Altura en habitantes de la ciudad de La Paz. de ambos sexos y diferentes grupos etéreos?. Objetivo general: Determinar si existe relación entre la concentración de Acido Urico sérico y la Eritrocitosis de Altura. Objetivos especificos. Determinar si existe correlación entre Acido Urico sérico y hematócrito, determinar si existe correlación entre Acido Urico sérico y Hemoglobina, conocer el valor promedio de Acido Urico a 3600 m s.n.m., conocer los datos estadísticos del comportamiento de las variables del estudio. Diseño de investigación: estudio de corte transversal. Lugar: Unidad de diagnóstico Molecular en hematologia Paolo Belli.Población: 98 casos y 118 controles por cálculo muestral en ambos sexos y de grupos etéreo diverso, que cumplieron los criterios de inclusión y exclusión. Metodos para cada uno de los pacientes se llenó un cuestionario con datos pesonales, identificación del paciente, edad, sexo y antecedentes de enfermedades previas. Metodos: La dosificación de ácido urico se realizó por el método espectrofotométrico de Caraway con desproteinización, en suero obtenido por centrifugación de sangre venosa recogida en tubo seco, habiéndose realizado un control de precisión permanente con sueros control. Las pruebas hematológicas se realizaron en sangre venosa anticoagulada, el microhematocrito se obtuvo utilizando una microcentrifuga a 10,000 rpm por 10 minutos, la dosificación de hemoglobina se realizó por el método espectrofotométrico de la cianmetahemoglobina. Para los cálculos estadísticos, se utilizó el paquete estadístico STATA 6.0. Se realizó el análisis descriptivo utilizando mediadas de tendencia central y de dispersión como promedio y desviación estándar, verificando a través del cálculo de intervalo de confianza 95 porciento, ademas de T test, chi2, coeficiente de correlación (rho) y prueba de Spearman. Resultados. Se observo que existe diferencias estadísticamente significativas entre los grupos enfermos y sanos con relación a las variables estudiadas. Ademas existe una correlación positiva entre el ácido úrico y la Eritrocitosis de altura mostrando las pruebas de Spearman un valor p<0.000, La edad en relación con ácido úrico, Ht, Hb no presentan correlación. Conclusiones: El ácido úrico presenta correlación positiva en los pacientes con eritrocitosis del Altura.(au)

Análisis estadístico de resultados del laboratorio clínico. I: ácido úrico / Statistical analysis of clinical laboratory data. I: uric acid

Mediante el análisis estadístico de la información acumulada en un laboratorio clínico se ha obtenido para la concentración de Acido Urico (AU) en sangre su ditribución teórica, la cual permite clasificar nuevos datos de dicha variable en el porcentil correspondiente. Esta alternativa supera en precisión al criterio de clasificación que ofrecen los amplios intervalos de Valores Normales que generalmente acompañan a las determinaciones clínicas en suero (Acido Urico, Colesterol, Triglicéridos, etc.). Asimismo a partir del estudio de Correlación y Regresión entre la concentración de AU y otras variables clínicas, y de éstas con parámetros como edad y sexo, se desarrollan criterios de contraste para el AU específicos para edad, sexo, Colesterol y Triglicéridos. Con estos criterios se enriquece la información que ofroce cada dato de AU para el diagnóstico clínico al mismo tiempo que proporcionan al laboratorio una herramienta útil para el control de calidad de los datos que produce

A solubility problem in the preparation of uric acid standards.

Consistently high (13-16%) uric acid values for quality control sera were found when using freshly-prepared working uric acid standards on the Autoanalyser II system. After investigation several conclusions are made, with the recommendation that working uric acid standards are best diluted with pH 9.5 glycine buffer (0.007 M).