Urinary & serum oxalate determination by oxalate oxidase immobilized on to affixed arylamine glass beads.

BACKGROUND & OBJECTIVE: Although the measurement of oxalate in urine and serum by Amaranthus leaf oxalate oxidase immobilized on free arylamine glass beads is highly sensitive and specific, the handling of glass beads is tedious and cumbersome. The present study was undertaken to overcome this problem. METHODS: Partially purified Amaranthus spinosus leaf oxalate oxidase was immobilized through diazotization onto arylamine glass beads affixed on the surface of a plastic strip by a non reactive fixative and employed for oxalate determination in urine and serum samples collected from healthy individuals and urinary stone formers. RESULTS: The immobilized enzyme retained 56 per cent of its initial activity with a conjugation yield of 40 mg/g support. The strip bound enzyme showed maximum activity at pH 3.5 when incubated at 40 degrees C for 15 min. The minimum detection limit of the method was 0.01 mM/l in the urine and 2.5 microM/l in the serum. The analytical recovery of added oxalate was 97.7+/-1.2 per cent in urine and 92.0+/-2.4 per cent in serum. Within and between assay coefficient of variation (CV) were 4.6 and 5.2 per cent in urine and 7.4 and 5.8 per cent in serum respectively. A good correlation for oxalate in urine (r1= 0.99) and in serum (r2= 0.92) was obtained between Sigma kit method and the present method. The strip could be reused 150 times over a period of 2 months, when stored at 4 degrees C in reaction buffer. INTERPRETATION & CONCLUSION: Immobilization of Amaranthus leaf oxalate oxidase on to affixed glass beads provided enormous ease in its reuse for determination of oxalate in urinary and serum samples.

Evaluation of calculated low-density lipoprotein against a direct assay.

OBJECTIVES: To evalate compare the calculated LDL determined by the Friedewald formula when Tg < 200 mg/dL, 200-399 mg/dL, and > or =400 mg/dL against a direct method. MATERIAL AND METHOD: Samples from 202 participants (122 males, 80 females, aged 20-87 years old) were determined for cholesterol, triglyceride (Tg), high-density lipoprotein (HDL), and low-density lipoprotein (LDL) at Department of Laboratory Medicine, King Chulalongkorn Memorial Hospital (KCMH). LDL was determined by Friedewald formula and a direct method. RESULTS: Intra-assay and inter-assay precisions at Tg <200 mg/dL, 200-399 mg/dL, > or =400 mg/dL of calculated LDL and direct LDL were 4.80%, 3.29%, 20.37%, 4.86, 8.42%, 8.32%, 2.11%, 1.79%, 3.99%, 2.36%, 2.41% and 6.16%, respectively. The mean absolute biases calculated for calculated LDL against direct LDL at Tg <200 mg/dL, 200-399 mg/dL, > or =400 mg/dL and for total samples were 4.70%, 11.73%, 63.65%, and 7.46%, respectively. Linear regression analysis for calculated LDL vs direct LDL for total samples and grouped as Tg <200 mg/dL, 200-399 mg/dL, and > or =400 mg/dL were 0.9190, 0.9796, 0.9440, and 0.7910, respectively. Intraclass correlation coefficient (ICC) at 95% confidence interval of calculated LDL against direct LDL at Tg <200 mg/dL, 200-399 mg/dL, > or =400 mg/dL and for total samples were 0.963, 0.930, 0.767, and 0.889, respectively. CONCLUSION: The present data suggested that direct LDL is superior over calculated LDL in terms of precision and accuracy. The present study supported that at Tg > or =400 mg/dL calculated LDL should not be used and the traditional cutoff of Tg <400 mg/dL for using Friedewald formula should be revised. In addition, regarding patient convenience, financial reason, and precision and accuracy of analytical method, direct LDL is recommended when Tg > or =200 mg/dL.

El rol del bioquímico clínico en los comentarios interpretativos: Criterios para su desarrollo / The role of the clinical biochemist in the interpretative commentaries: Criteria for its development

El establecimiento de la Mejora Contínua de la Calidad en los servicios de los laboratorios, ha llevado a la fijación de estándares de trabajo, monitoreo de indicadores de gestión y a la creación de ambientes donde se trata de optimizar permanentemente la atención a los pacientes. La clarificación de la posible significación de los resultados y reportes y su adecuada comunicación es una parte de la etapa post-analítica cada vez más importante dentro de la tarea de los bioquímicos. Consideramos que los informes interpretativos deben ser emitidos en todos los casos por el profesional que valida el informe, convenientemente entrenado para este tipo de comunicaciones y con el conocimiento y supervisión de sus superiores. Para ser útiles, los comentarios interpretativos deben ser certeros, sucintos y estar adaptados a los conocimientos y experiencia del receptor a fin de proporcionar la mayor información clínicamente útil. Excepto en los casos en los que es posible un contacto directo con el médico para discutir los resultados o cuando se conoce la evolución de un caso, no existe oportunidad para el bioquímico de aprender por medio del feedback y así aumentar sus habilidades interpretativas. Si somos capaces de producir resultados útiles, de alta calidad analítica y de poder interpretarlos, debemos procurar que la comunicación con los demás integrantes del Equipo de Salud sea fluída para la mejor utilización de todo lo que el laboratorio puede ofrecer. Es parte de nuestra tarea la interpretación de los datos desde la visión bioquímica como aporte valioso para el desempeño de la labor médica y la armoniosa integración del Equipo de Salud.

Standardization of the method for estimation of ethambutol in pharmaceutical preparations and biological fluid.

A simple column chromatographic method for determination of ethambutol (EMB) in pharmaceutical preparations containing EMB in combination with other anti-TB drugs is presented. The method involved extraction of EMB into an organic solvent, followed by basification and column chromatographic separation on Amberlite CG 50 (100-200 mesh) and elution with suitable eluants and estimation at a wavelength of 270 nm. The assay was linear from 25 to 400 microg/ml. The relative standard deviations of intra and inter day assays were lower than 5%. Ethambutol was recovered from human urine quantitatively and stable for a period of at least one week in urine stored at -20 degrees C.

An enzymatic method for the detection of human serum albumin

Albumin is the most abundant protein in human serum. A dye-binding method is commonly used in clinical laboratories for its estimation using different types of dyes. However, all these dye methods were interfered by a variety of compounds. Here we present a method for the detection of albumin in human serum and other biological fluids. The principle is based on the fact that lactate dehydrogenase isoenzyme-5 (LDH-5) binds specifically to Dextran-Blue (DB). Albumin inhibits the binding of LDH-5 with DB. Absence of LDH activity in DB fraction after gel filtration indicates the presence of albumin in sample and vice versa.

Differential application of rate and delta check on selected clinical chemistry tests

Through the present delta value check used in quality control programs is a powerful tool for detecting random errors in clinical chemistry analysis, it has some problems, such as missed true errors and delays in reporting time, because it also has the potential of showing erroneous positive results. Recently, new calculation methods for delta check with delta difference, delta percent change, rate difference, and rate percent change have been suggested by Lacher and Connelly (Clin Chem 34:1966-1970, 1988). Based on this new delta check method, we made the new criteria of which calculation method is applied to the clinical chemistry tests, i.e., the differential application of rate and delta check, and selectively applied the new method to 17 chemistry tests in order to solve the above problems. The applied criteria were the time dependence of the test item and the coefficient of variation of the absolute delta difference. Calcium, inorganic phosphorus, total protein, albumin, sodium, potassium, and chloride were classified as delta difference calculation method group; glucose and cholesterol as delta percent change group; creatinine, total and direct bilirubin as rate difference group; and urea nitrogen, uric acid, ALP, ALT, and AST as rate percent change group. With the previous criteria by Whitehurst et al. (Clin Chem 221:87-92) for 5045 specimens, the check-out rate was 47.8% (2,411 out of 5,045), and the positive predictive value was 0.41% (10 out of 2,411). For the new criteria, the check-out rate was 12.7% (621 out of 5,045), and the positive predictive value was 1.8% (nine out of 621).(ABSTRACT TRUNCATED AT 250 WORDS)