Ellis Jacobs

Approved IFCC recommendation on reporting results for blood glucose

Abstract In current clinical practice, plasma and blood glucose are used interchangeably with a consequent risk of clinical misinterpretation. In human blood, 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, but the concentration is higher in plasma, because the concentration of water and therefore glucose is higher in plasma than in erythrocytes. Different devices for the measurement of glucose may detect and report fundamentally different quantities. Different water concentrations in the calibrator, plasma, and erythrocyte fluid can explain some of the differences. Results for glucose measurements depend on the sample type and on whether the method requires sample dilution or uses biosensors in undiluted samples. If the results are mixed up or used indiscriminately, the differences may exceed the maximum allowable error for glucose determinations for diagnosing and monitoring diabetes mellitus, thus complicating patient treatment. The goal of the International Federation of Clinical Chemistry and Laboratory Medicine, Scientific Division, Working Group on Selective Electrodes and Point of Care Testing (IFCC-SD-WG-SEPOCT) is to reach a global consensus on reporting results. The document recommends reporting the concentration of glucose in plasma (in the unit mmol/L), irrespective of sample type or measurement technique. A constant factor of 1.11 is used to convert concentration in whole blood to the equivalent concentration in plasma. The conversion will provide harmonized results, facilitating the classification and care of patients and leading to fewer therapeutic misjudgments. Clin Chem Lab Med 2006;44:1486–90.

IFCC guideline for sampling, measuring and reporting ionized magnesium in plasma.

Abstract Analyzers with ion-selective electrodes (ISEs) for ionized magnesium (iMg) should yield comparable and unbiased results for iMg. This IFCC guideline on sampling, measuring and reporting iMg in plasma provides a prerequisite to achieve this goal [in this document, “plasma” refers to circulating plasma and the forms in which it is sampled, namely the plasma phase of anticoagulated whole blood (or “blood”), plasma separated from blood cells, or serum]. The guideline recommends measuring and reporting ionized magnesium as a substance concentration relative to the substance concentration of magnesium in primary aqueous calibrants with magnesium, sodium, and calcium chloride of physiological ionic strength. The recommended name is “the concentration of ionized magnesium in plasma”. Based on this guideline, results will be approximately 3% higher than the true substance concentration and 4% lower than the true molality in plasma. Calcium ions interfere with all current magnesium ion-selective electrodes (Mg-ISEs), and thus it is necessary to determine both ions simultaneously in each sample and correct the result for Ca2+ interference. Binding of Mg in plasma is pH-dependent. Therefore, pH should be measured simultaneously with iMg to allow adjustment of the result to pH 7.4. The concentration of iMg in plasma may be physiologically and clinically more relevant than the concentration of total magnesium. Furthermore, blood-gas analyzers or instruments for point-of-care testing are able to measure plasma iMg using whole blood (with intact blood cells) as the sample, minimizing turn-around time compared to serum and plasma, which require removal of blood cells. Clin Chem Lab Med 2008;46:21–6.

Implementation, management and continuous quality improvement of point-of-care testing in an academic health care setting.

Point-of-care testing (POCT) has economic and medical benefits in the areas of immediate medical management, resource utilization and time management. Starting with bedside glucose, the Mount Sinai Medical Center has, over the past 11 years, implemented 23 POC tests, spanning complexity from blood gas/electrolyte testing to occult blood, in compliance with all regulatory and accreditation requirements. QC data are reviewed on a daily and weekly basis and all patient results are in the electronic medical record. A variety of healthcare workers; nurses, physicians, respiratory therapists and technologists, perform testing. Since POCT impacts on a variety of hospital departments, proper implementation and management requires a multi-disciplinary team approach with focus on the financial, regulatory, quality assurance and data integration issues. Established in 1996, the institutional committee, with laboratory leadership, handles the establishment, compliance review and future direction setting of the program. In 1999, over 1300 individuals performed over 440,000 POC tests within the institution. A formalized continuous quality improvement (CQI) program for the POCT program was developed in the fall of 1999. All testing sites are reviewed on a monthly basis for various quality indicators that cover QC performance, maintenance performance, proficiency testing, patient identification, and alert value confirmations.

Guidelines for sampling, measuring and reporting ionized magnesium in undiluted serum, plasma or blood: International Federation of Clinical Chemistry and Laboratory Medicine (IFCC): IFCC Scientific Division, Committee on Point of Care Testing.

Abstract All analyzers with ion-selective electrodes for ionized magnesium (iMg) should yield comparable and unbiased results. The prerequisite to achieve this goal is to reach consensus on sampling, measurement and reporting. The recommended guidelines for sampling, measurement and reporting iMg in plasma (“plasma” refers to circulating plasma and the forms in which it is sampled: the plasma phase of anticoagulated whole blood, plasma separated from blood cells, or serum) or blood, referring to the substance concentration of iMg in the calibrants, will provide results for iMg that are approximately 3% greater than its true concentration, and 4% less than its true molality. Binding of magnesium to proteins and ligands in plasma and blood is pH-dependent. Therefore, pH should be simultaneously measured to allow adjustment of iMg concentration to pH7.4. The substance concentration of iMg may be physiologically and consequently clinically more relevant than the substance concentration of total magnesium.

Recommendation for measuring and reporting chloride by ISEs in undiluted serum, plasma or blood.

Abstract The proposed recommendation for measuring and reporting chloride in undiluted plasma or blood by ion-selective electrodes (ISEs) will provide results that are identical to chloride concentrations measured by coulometry for standardized normal plasma or blood samples. It is applicable to all current ISEs dedicated to chloride measurement in undiluted samples that meet the requirements. However, in samples with reduced water concentration, results by coulometry are lower than by ion-selective electrode due to volume displacement. The quantity measured by this standardized ISE procedure is called the ionized chloride concentration. It may be clinically more relevant than the chloride concentration as determined by coulometry, photometry or by ISE after dilution of the sample.

IFCC News January 2001

For many people throughout the world, the year 2000 has been a year of festivity, marking the arrival of a new millennium. There has been some discussion as to whether the first year of the millennium should be, in reality, the year 2001. No doubt they will be celebrating in turn, and thinking of the future that lies ahead. Whether 2001 is the first or second year is perhaps less important than knowing where you will go in the new millennium. IFCC has achieved much since its inception, but it has more to achieve in the future. Laboratory medicine is changing through new knowledge of molecular and genetic processes, while healthcare economics make it necessary to use existing knowledge more efficiently. With the dynamic vision of its new leadership, there are new strategic goals for IFCC to play a leading role in the laboratory medicine response to both of these pressures, and there are new tools in technology and telecommunications that can help achieve this. IFCC plans to build on its existing strong foundations and to expand, becoming an internationally networked organisation that co-ordinates and harmonises standardisation efforts in laboratory sciences; acts as a source of advice for individual scientists, professional associations, governmental and non-governmental agencies on technical and managerial issues; promotes exchanges such as twinning programmes to provide education and training; and facilitates interactions with the corporate members whose companies produce many of the materials used in the laboratory. A new handbook describing the internal organisation of IFCC that should make these goals possible can be read or downloaded from the web-site http://www.ifcc.org. At the same time as addressing what laboratory medicine can do for the individual patient, IFCC has been thinking about the technological advances that can make its own organisation more efficient in terms of internal communication and interactions with its membership-the national societies of laboratory sciences, the individual scientists of these societies, and the corporate members. Already active with its website and electronic publications, IFCC’s cyberspace odyssey can be expected to continue in 2001. As ecommunication and e-commerce tools become more reliable, more affordable, and more easily accessed around the globe, then IFCC will evaluate and incorporate those electronic tools that enable it to satisfy the needs of its membership and, in doing so, to contribute to better patient care throughout all the regions of the world. Watch this space to discover more ...!