IFCC recommendation on reporting results for blood glucose.

In human beings, glucose is distributed like water between erythrocytes and plasma. The molality of glucose (amount of glucose per unit water mass) is the same throughout the sample. Different water concentrations in calibrator, plasma, and erythrocyte fluid can explain some differences that are dependent on sample type, methods requiring sample dilution, and direct reading biosensors detecting molality. Different devices for the measurement of glucose detect and report fundamentally different analytical quantities. The differences exceed the maximum allowable error of glucose determinations for diagnosing and monitoring diabetes mellitus, and they complicate the treatment. The goal of the International Federation of Clinical Chemistry, Scientific Division, Working Group on Selective Electrodes (IFCC-SD WGSE) is to reach a global consensus on reporting results. The document recommends harmonizing to the concentration of glucose in plasma (with the unit mmol/l), irrespective of sample type or technology. A constant factor of 1.11 will convert measured concentration in whole blood to the equivalent concentration in plasma.

Use of ion-selective electrodes for blood-electrolyte analysis. Recommendations for nomenclature, definitions and conventions. International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). Scientific Division Working Group on Selective Electrodes.

This paper will familiarize the reader with the terms used to describe the behavior of ion-selective electrodes, particularly in relation to their use in clinical chemistry for determination of blood electrolyte cations. It serves as an introduction to a series of papers dealing with important cations in blood, namely calcium, sodium, and potassium. The detailed relationships between the ion activity determined by means of ion-selective electrode potentiometry in undiluted specimens, and the total substance concentration measured by flame atomic-emission spectrometry are described by flow chart and equations. Adoption of a convention for reporting results is recommended. The Working Group on Selective Electrodes has taken into account recent revisions of IUPAC recommendations on nomenclature and selectivity coefficient determinations for ion-selective electrodes, and benefited from the experience of a member of the WG, who was also involved in the IUPAC discussions. Nomenclature for determined quantities follows previous IUPAC/IFCC joint recommendations.

IFCC recommended reference method for the determination of the substance concentration of ionized calcium in undiluted serum, plasma or whole blood.

A reference method is described for the determination of the substance concentration of ionized calcium in plasma by which ionized calcium (free or unbound) may be reliably determined on the basis of calibration with aqueous solutions with known concentration of ionized calcium. The composition of the calibration solutions is chosen such that the activity coefficient of the calcium ion is assumed to be identical both in the calibration solutions and in "normal" plasma, i.e. by convention, the ionic strength (Im) is 0.160 mol/kg. The convention is adopted of reporting ionized calcium measurements as concentration expressed as mmol/l. The proposed reference method for ionized calcium measurement in plasma is based on the use of a cell consisting of an external reference electrode with a saturated potassium chloride liquid/liquid junction in combination with a calcium ion-selective membrane electrode of defined construction and performance. Procedures for using the reference cell and a protocol for sample measurement are described. The preparation of the calibration solutions to be used are described in detail in Appendix A, secondary calibration solutions and check standards in Appendix B, and reference cell vessel design in Appendix C.

Recommendations for measurement of and conventions for reporting sodium and potassium by ion-selective electrodes in undiluted serum, plasma or whole blood. International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). IFCC Scientific Division Working Group on Selective Electrodes.

Ion-selective electrodes (ISEs) respond to ion-activity and therefore do not sense substance concentration directly. However, it is recognized that sodium and potassium in plasma will continue to be expressed for clinical purposes in terms of substance concentration (mmol/l). A convention is proposed whereby for routine clinical purposes results of ISE measurements of sodium and potassium in undiluted plasma should be reported in terms of substance concentration (mmol/l). In specimens with normal concentrations of plasma water, total CO2, lipids, protein and pH, the values will concur with the total substance concentration as determined for example by flame atomic emission spectrometry (FAES) or ISE measurements on diluted samples. In specimens with abnormal concentrations of plasma water, the results will differ. However, under these circumstances, measurements of sodium and potassium by ISE in the undiluted sample will more appropriately reflect the activity of sodium and potassium and are therefore clinically more relevant than the determination in diluted samples. Detailed recommendations are made about practical procedures to achieve this. The recommended name for this quantity is the substance concentration of ionized sodium or ionized potassium in plasma, as opposed to total sodium or total potassium determined by, e.g. FAES, or ISE measurements on diluted samples.

International Federation of Clinical Chemistry (IFCC). Recommendation on mean molar activity coefficients and single ion activity coefficients of solutions for calibration of ion-selective electrodes for sodium, potassium and calcium determination.

In principle, flame photometry measures substance concentration, and ion-selective electrodes (ISEs) measure ion activity. However, the situation regarding the comparison of results from the two techniques when applied to blood plasma is complex. The problem can be approached experimentally from the point of view of calibration of ion-selective electrodes with concentration calibrators, and similar procedures are adopted for commercial ISE-based clinical analysers. Nevertheless, there is interest in the evaluation of single ion activities in blood plasma and solutions simulating its ionic composition. Solutions are proposed for calibrating ion-selective electrodes for the determination of sodium, potassium and calcium. It is recommended that the values for single ion activities derived from the Pitzer treatment of mixed electrolyte solutions be adopted, because, although this has some empirical features, it has a sounder theoretical basis than the previously used Stokes-Robinson-Bates hydration approach.

Recomendações para coleta, transporte e armazenamento de sangue total para determinações simultâneas de PH, gases e eletrólitos / Recommendations on whole blood sampling, transport and storage for simultaneous determination of PH, blood gases and electrolytes

As variáveis pré-analíticas: coleta, transporte e armazenamento, podem contribuir significativamente para a imprecisão dos valores de pH, gasometria e eletrólitos. A International Federation of Clinical chemistry (IFCC), através de seus comitês em pH, Gases Arteriais e eletrólitos, tem publicado recomendações específicas com o intuito de minimizar os efeitos indesejáveis das variáveis pré-analíticas. Estes comitês se basearam na experiências de seus próprios membros, como também em artigos publicados por outros. Especificamente, os comitês têm incluído rotinas e sugestões confeccionadas pelos: IFCC Working Group on Selective Electrodes (WGSE), National Committee on Clinical Laboratory Standards (NCCLS), Eletrolyte/Blood Gás Division of the American Association for Clinical Chemistry (AACC). Este artigo irá familiarizar o leitor com os efeitos de diferentes tipos de frascos e anticoagulantes. Também serão discutidos aspectos importantes dos procedimentos de coleta, incluindo o estado do paciente e as precauções especiais a serem tomadas quando utilizam-se catéteres ou cânulas para a coleta. Serão vistos também as diferentes normas para o armazenamento e tranporte das amostras, para as análises gasométrica e eletrolítica.

International Federation of Clinical Chemistry (IFCC), Committee on pH, Blood Gases and Electrolytes: approved IFCC recommendation on definitions of quantities and conventions related to blood gases and pH.

Terminology in blood pH and gas analysis can be confusing, both because more than one name has been used for the same quantity, and because the same name has been used for more than one quantity. In addition, several calculated quantities are commonly used, but in some cases many different algorithms have been published for a single quantity. This document contains definitions of the most useful quantities in blood pH and gas analysis, and presents algorithms for the most useful calculated quantities. Use of these should lessen confusion among users and should also result in data that are more comparable among laboratories.

International Federation of Clinical Chemistry (IFCC). Scientific Division. Committee on pH, Blood Gases and Electrolytes. Approved IFCC recommendations on whole blood sampling, transport and storage for simultaneous determination of pH, blood gases and electrolytes.

Pre-analytical variables, e.g., specimen collection, transport, and storage, can contribute significantly to inaccurate pH, blood gas, and electrolyte values. The International Federation of Clinical Chemistry (IFCC), through its Committee on pH, Blood Gases and Electrolytes, has developed specific recommendations to minimize the undesirable effects of pre-analytical variables. The Committee has drawn upon the experiences of its own members as well as published data by others. Specifically, the Committee has included pertinent guidelines and suggestions by the IFCC Working Group on Selective Electrodes (WGSE), the National Committee on Clinical Laboratory Standards (NCCLS), and the Electrolyte/Blood Gas Division of the American Association for Clinical Chemistry (AACC). This paper will familiarize the reader with the effect of different types of specimen containers and anticoagulants. It discusses important aspects of specimen collection procedures including patients status and special precautions during specimen collection from indwelling catheters or cannulae. The paper also identifies different requirements in storage and transport of specimens for blood gas and electrolyte analysis.

Current status of sweat testing in North America. Results of the College of American Pathologists needs assessment survey.

The College of American Pathologists surveyed 5096 laboratories for information concerning collection and analytic methodologies used in the performance of the sweat test. The test measures the concentration of electrolytes in sweat and is an essential criterion for the diagnosis of cystic fibrosis. An 83% response rate was achieved on the needs assessment survey, representing the first large-scale, national study of sweat testing practices. Nineteen percent of the respondents perform sweat testing in their laboratory, and the majority of the respondents analyze the sweat for chloride concentration. Fifty-nine percent of the laboratories performing sweat testing indicated an interest in participating in proficiency testing for sweat analysis. The information gathered from the needs assessment survey will be used to develop a comprehensive proficiency testing program to provide feedback and education to laboratories performing this critical diagnostic test.

Recommendations on whole blood sampling, transport, and storage for simultaneous determination of pH, blood gases, and electrolytes. International Federation of Clinical Chemistry Scientific Division.

Pre-analytical variables, e.g., specimen collection, transport, and storage, can contribute significantly to inaccurate pH, blood gas, and electrolyte values. The International Federation of Clinical Chemistry (IFCC), through its Committee on pH, Blood Gases and Electrolytes, has developed specific recommendations to minimize the undesirable effects of pre-analytical variables. The Committee has drawn upon the experiences of its own members as well as published data by others. Specifically, the Committee has included pertinent guidelines and suggestions by the IFCC Working Group on Selective Electrodes (WGSE), the National Committee on Clinical Laboratory Standards (NCCLS), and the Electrolyte/Blood Gas Division of the American Association for Clinical Chemistry (AACC). This paper will familiarize the reader with the effect of different types of specimen containers and anticoagulants. It discusses important aspects of specimen collection procedures including patient status and special precautions during specimen collection from indwelling catheters or cannulae. The paper also identifies different requirements in storage and transport of specimens for blood gas and electrolyte analysis.

Matrix effects in blood gas proficiency testing.

Materials currently used for blood gas proficiency testing are unlike whole blood in several obvious respects, which by definition introduces matrix effects as possible sources of error that can affect proficiency testing results. Data from recent College of American Pathologists surveys are reviewed and aqueous and fluorocarbon matrices for PO2 and PCO2 testing are compared. Closely related to matrix effects are other sources of error unique to proficiency testing samples, such as sample temperature and sample packaging. Proficiency testing programs are seriously hampered by not being able to use either whole blood or a better surrogate than is currently available. In particular, the use of aqueous materials has the potential to penalize participant laboratories unfairly in some cases and to turn proficiency testing into a meaningless exercise in others.

Activities of the Committee on pH, Blood Gases and Electrolytes, International Federation of Clinical Chemistry, 1977-1992.

Among the many contributions of Ole Siggaard-Andersen to the field of clinical chemistry, one of the most significant is his fifteen-year participation in the work of the Committee on pH, Blood Gases and Electrolytes of the International Federation of Clinical Chemistry. This is a brief summary of the mission and accomplishments of that committee.

Selection of measurement and control procedures to satisfy the Health Care Financing Administration requirements and provide cost-effective operation.

The basic principles of method evaluation and quality control system design have been extensively studied and described. However, the interaction among the various independent variables comprising the complete analytical system is not so well known. In this article, a model of a generalized analytical system is presented and the nature of the interaction among analytical method parameters and quality control system parameters is explored. Implications of recent Health Care Financing Administration regulations for allowable total error are also discussed.

Guidelines for routine measurement of blood hemoglobin oxygen affinity. IFCC Scientific Division, Committee on pH, Blood Gases, and Electrolytes.

Two methods for the routine determination of blood hemoglobin oxygen affinity are described. Both methods use whole blood and do not require special equipment, tonometry, or special gas mixtures. The first method consists of a one-point determination of p 50, and requires only 200 muL to 400 muL of whole blood, therefore making it suitable for the pediatric population. The second method uses multiple points, thereby establishing both the shape and position of the hemoglobin oxygen equilibrium curve between 10 and 99% oxygen saturation. Interpretation of p 50 is discussed in relation to evaluation of patients with hemoglobinopathies and as a parameter in estimating availability of oxygen to the tissues.

Quality management science in clinical chemistry: a dynamic framework for continuous improvement of quality.

Current quality assurance approaches will not be adequate to satisfy the needs for quality in the next decade. Quality management science (QMS), as evolving in industry today, provides the dynamic framework necessary to provide continuous improvement of quality. QMS emphasizes the importance of defining quality goals based on the needs and expectations (implied needs) of customers. The laboratory can develop customer-friendly goals and measures of quality by recognizing that customers' experiences are represented by a totality of results. Quality goals and measures are best communicated as "total performance" by specifying a limit and percentile of the distribution, rather than a mean and standard deviation. Application of quality goals within the laboratory will usually require partitioning the total performance goal into components and translating those components into specifications to guide the operation and management of production processes. QMS also extends beyond technical processes to people processes and provides guidance for improving the quality of worklife and caring for the laboratory's most essential resource--our people.

International Federation of Clinical Chemistry (IFCC). Scientific Division. Committee on pH, Blood Gases and Electrolytes. Guidelines for transcutaneous pO2 and pCO2 measurement.

This document provides guidelines in the terminology, methodology, and in the interpretation of data obtained from the use of skin (transcutaneous) pO2 and pCO2 electrodes. The transcutaneous technique has found special application in newborn infants. The causes of analytical bias with respect to arterial blood gas values and imprecision obtained with transcutaneous pO2 and pCO2 electrodes are reviewed. Electrode temperatures above 44 degrees C should not be used routinely, and at a measuring temperature of 44 degrees C, the measuring site should be changed at least every 4 h to avoid skin burning.

Precision requirements for cost-effective operation of analytical processes.

Current performance criteria for analytical methods are often based on recommendations developed many years ago. A common criterion for imprecision requires that two times the standard deviation (s) of the method be less than the allowable total error (TEa). Unfortunately, when this criterion is minimally satisfied, commonly used control procedures cannot achieve reliable detection of medically important errors. Studies of the power functions for statistical quality-control (QC) procedures show that the magnitude of medically important errors must be at least 3s to fall near the plateau of the power curves and be readily detected by current QC procedures. For methods that just meet the precision criterion 2s less than TEa, however, medically important errors will fall on the rising portion of the power curves and typically be detected less than half of the time. From a "reverse engineering" perspective, the 2s less than TEa criterion is inadequate because it does not allow for the known performance limitations (lack of sensitivity) of commonly used control procedures. A strong case can be made for using a criterion of at least '4s less than TEa, which calls for a twofold improvement in imprecision over, the current minimum requirements. This recommendation is consistent with current industrial guidelines for process capability and would lead to more reliable detection of medically important errors.

Método IFCC (1988) para tonometria de sangre; materiales de referencia para Pco2 y Po2 / IFCC método (1988) from blood of tonometry; Pco2 and Po2 reference of material

Se describe un método de referencia para tonometría de la sangre. El documento abarca la teoria de la tonometría, los materiales y el equipo necesarios y los aspectos esenciales del procedimiento de tonometría para sangre. Las presiones parciales de oxígeno y dióxido de carbono en sangre tonometrada son conocidas exactamente y, por lo tanto, esta sangre se recomienda para evaluación de la exactitud de analizadores de gases sanguíneos. La tonometría de muestras de sangre de pacientes puede ser también usada en la determinación de cantidades ácido-base y de la afinidad hemoglobina-oxigeno e.g.Pso.