Comparison and commutability study between standardized liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) and chemiluminescent enzyme immunoassay for aldosterone measurement in blood

A commutability confirmation test for the blood aldosterone measurement was performed on liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) as a designated comparison method (DCM) and four chemiluminescent enzyme immunoassay (CLEIA) measurement procedures based on metrological traceability. A conventional radioimmunoassay (RIA) and two measurement procedures of CLEIA which obtains RIA equivalent values were also compared. The relationship between the DCM value and the CLEIA value with respect to 120 pg/mL of the RIA value, which is the screening criterion of primary aldosteronism (PA) was clarified. For the correlation test, 75 samples of patient serum and plasma were used. Regression analysis revealed that the standardized LC-MS/MS and four CLEIA measurement procedures were in good agreement. This is the effect of measurement specificity and calibration using by certified reference material (CRM). The median of the LC-MS/MS corresponding to 120 pg/mL of RIA was 48.5 pg/mL. In the mean of standardized four CLEIA values corresponding to the 48.5 pg/mL of LC-MS/MS value was 47.51 pg/mL and the standard deviation (SD) was 2.93 pg/mL. However, the correlation between the RIA value and the RIA equivalent of the two measurement procedures by CLEIA differed depending on the measurement procedure. This is due to the influence of RIA measurement performance. Standardized CLEIA measurements are suitable for routine measurement procedure. When converting the LC-MS/MS equivalent value by the standardized CLEIA to the conventional RIA value, it is necessary to use the conversion formula.

Calibration and evaluation of routine methods by serum certified reference material for aldosterone measurement in blood

We attempted to study the standardization of aldosterone measurement in blood. The serum certified reference material (serum CRM) was established by spiking healthy human serum with pure aldosterone. ID-LC/MS/MS as a reference measurement procedure was performed by using the serum CRM. LC-MS/MS as a comparison method (CM) was routinely used for clinical samples, and the values with and without calibration by the serum CRM were compared. The serum CRM demonstrated similar reactivity with peripheral blood plasma as clinical samples in routine methods (RM) of RIA, ELISA, and CLEIA. In comparison between RM and CM, the results in regression analysis indicated that the range of the correlation coefficient (r) was 0.913 - 0.991, the range of y intercept was 0.9 - 67.3 pg/mL and the range of slope was 0.869 - 1.174. The values by RM in 100 - 150 pg/mL for the diagnostic level, had a significant calibration effect, and the relative difference between calibrated value in RM and result by CM was within ±20%. Furthermore, the calibrated value using the serum CRM was 10,187 pg/mL, which corresponds to measured value of 14,000 pg/mL using RIA for the adrenal venous sampling. Measured values between plasma and serum as a sample for the aldosterone measurement from clinical samples showed no significant differences. In conclusion, we succeeded to prepare the certified reference material of aldosterone for RM. Then, we can accurately calculate corrected values by using our equation for four RMs of determination of aldosterone.

Japanese standard reference material JDS Lot 2 for haemoglobin A1c. II: Present state of standardization of haemoglobin A1c in Japan using the new reference material in routine clinical assays

Background: In 2001, the Committee on Standardization of Laboratory Testing Related to Diabetes Mellitus of the Japan Diabetes Society (JDS) prepared and certified a new reference material for haemoglobin A1c (HbA1c), Lot 2. The standardization programme for HbA1c measurement in Japan is currently based on Lot 2, although some laboratories still use the previous material (Lot 1). The values assigned to Lot 2 were based on the consensus values for Lot 1 and should give the same results. Therefore, there should be no difference in the measured values no matter which calibrators are used. The Committee conducted a domestic survey in order to confirm this relationship.

Method: In November 2002, four samples for HbA1c assay were sent to 795 laboratories as part of a national survey in Japan. Assays were performed using the laboratories' routine clinical methods. The coefficients of variation (CVs) of the reported values from all laboratories for the samples were calculated in order to determine the current level of standardization in Japan.

Results: The overall CVs in the measured values for the four samples ranged from 2.7% to 4.0%. Values from laboratories using calibrators based on Lots 1 and 2 were similar.

Conclusion: The present state of standardization for the routine measurement of HbA1c in Japan, as indicated by the 2002 survey, is excellent. This should aid in the eventual conversion of Lot 2 to IFCC-based values from the results of the 2002 national HbA1c survey.

Committee on Diabetes Mellitus Indices of the Japan Society of Clinical Chemistry-recommended reference measurement procedure and reference materials for glycated albumin determination

Background

Glycated albumin is an intermediate glycaemic control marker for which there are several measurement procedures with entirely different reference intervals. We have developed a reference measurement procedure for the purpose of standardizing glycated albumin measurements.

Methods

The isotope dilution liquid chromatography/tandem mass spectrometry method was developed as a reference measurement procedure for glycated albumin. The stable isotopes of lysine and fructosyl-lysine, which serve as an internal standard, were added to albumin isolated from serum, followed by hydrogenation. After hydrolysis of albumin with hot hydrochloric acid, the liberated lysine and fructosyl-lysine were measured by liquid chromatography/tandem mass spectrometry, and their concentrations were determined from each isotope ratio. The reference materials (JCCRM611) for determining of glycated albumin were prepared from pooled patient blood samples.

Results

The isotope dilution–tandem mass spectrometry calibration curve of fructosyl-lysine and lysine showed good linearity (r = 0.999). The inter-assay and intra-assay coefficient of variation values of glycated albumin measurement were 1.2 and 1.4%, respectively. The glycated albumin values of serum in patients with diabetes assessed through the use of this method showed a good relationship with routine measurement procedures (r = 0.997). The relationship of glycated albumin values of the reference material (JCCRM611) between these two methods was the same as the relationship with the patient serum samples.

Conclusion

The Committee on Diabetes Mellitus Indices of the Japan Society of Clinical Chemistry recommends the isotope dilution liquid chromatography/tandem mass spectrometry method as a reference measurement procedure, and JCCRM611 as a certified reference material for glycated albumin measurement. In addition, we recommend the traceability system for glycated albumin measurement.

Report on HbA1c Proficiency Testing in Asia in 2012

In 2010, the Japan Diabetes Society decided to introduce the National Glycohemoglobin Standardization Program (NGSP) values into clinical practice. Accordingly, NGSP Certification of Japanese manufacturers of HbA1c-related diagnostic reagents and instruments was initiated in February, 2012, through an NGSP network laboratory, the Asian Secondary Reference Laboratory (ASRL) #1. Traceability to the NGSP reference system can be endorsed by manufacturer certification, as well as by the College of American Pathologists (CAP) survey. Nevertheless, only a few manufacturers participate in the CAP survey in Japan. Thus, proficiency testing (PT) was proposed and executed by ASRL #1. Single-donor whole-blood samples were used for the PT. The participated measurement systems were NGSP certified. Twenty-two laboratories obtained certification through ASRL #1; 2 through the Secondary Reference Laboratory (SRL) #8; and 9 through the SRL #9. The combination plots of the bias data in this PT and in the NGSP certification performed in March and May in 2012 were consistent with each other: mean NGSP values at each level agreed well with the target value. In conclusion, PT using whole blood is useful in endorsing NGSP certification.

[Internal Quality Control and External Quality Assessment on POCT]

The quality management (QM) of POCT summarizes its internal quality control (IQC) and external quality assessment (EQA). For QM requirements in POCT, ISO 22870-Point-of-care testing (POCT) -Requirements for quality and competence and ISO 15189-Medical laboratories-Requirements for quality and competence, it is performed under the guidance of the QM committee. The role of the POC coordinator and/or medical technologist of the clinical laboratory is important. On measurement performance of POCT devices, it is necessary to confirm data on measurement performance from the manufacturer other than those in the inserted document. In the IQC program, the checking and control of measurement performance are the targets. On measurements of QC samples by the manufacturer, it is essential to check the function of devices. In addition, regarding the EQA program, in 2 neighboring facilities, there is an effect to confirm the current status of measurement and commutability assessment in these laboratories using whole blood along with residual blood samples from daily examinations in the clinical laboratory.

[From the Point of View of the Production of Reference Material]

In the international standardization of lipid measurement for TC, HDL-C, LDL-C, and TG in serum, the establishment of a measurement system and certified serum reference materials (CRM) are the most important fundamental factor. They have been fully established. Routine measurement procedures using manufacturers' reagent kits must be calibrated with the CRM and are standardized to maintain the commutability of measured values. In TC and HDL-C measurements, the commutability of measured values from reagent kits has been maintained by calibration with the CRM. However, it is likely that different values will be obtained due to the reactivity with abnormal specimens based on measurement principles and performance of the reagent kits. This different reactivity is a typical phenomenon in abnormal specimens on conducting lipid measurements. This phenomenon cannot be avoided using the CRM. On selection of the reagent kit, it is necessary to perform evaluation studies using abnormal specimens based on the comparison method. Direct methods standardized for LDL-C measurement are selected based on evaluation studies. In TG measurements for international standardization, it is necessary to change the procedure to measure the total glycerides instead of the elimination of free glycerol by the JSCC method. This is done to avoid the influence of LPL activity on heparin treatment for cardiovascular disease patients.

[Report of immunoassay control surveys conducted in the past 30 years by the Subcommittee for Radioisotope in vitro Test, the Medical Science and Pharmaceutical Committee, and the Japan Radioisotope Association]

Immunoassay control surveys, were conducted by the Subcommittee for Radioisotope in vitro Test, the Medical Science and Pharmaceutical Committee, and the Japan Radioisotope Association, between 1978 to 2008. A total of 40 analytes for 26 hormones, 14 tumor markers and pharmaceutical drugs were investigated in participating facilities. In the first immunoassay control survey in 1978, samples were measured using only RI kits, however, non-RI kits increased gradually during the next 30 years. In the 30th immunoassay control survey, more than 90% samples were measured using non-RI kits. Coefficient variation (CV) of intra-kits has been decreasing yearly in all analytes for hormones as well as tumor markers. However, improvement of CV in inter-kits has not been seen in the past 30 years by a lack of international standards, although there has been continuous effort over the years for the standardization of immunoassay. Growth hormone (GH) deficiency has been diagnosed using various loading tests. However, the clinical diagnosis varies according to the GH kit used. Standardization for GH measurement has been possible by using recombinant GH as the standard among commercial GH kits. The diagnosis of subclinical Cushing's syndrome also varies according to the cortisol kits being used. Candidate reference measurement procedure and low level cortisol standards have been developed by the Biomedical Standard Section, of the National Metrology Institute of Japan. Standardization of measurement is necessary for improvement of immunoassay.

[Feasibility study for development of automatic calibration system for clinical laboratory analyzers]

This report summarizes the results of a "Feasibility Study for Development of Automatic Calibration System for Clinical Laboratory Analyzers", that was entrusted to the JCCLS (Japanese Committee for Clinical Laboratory Standards) as a project for 2007FY by the Mechanical Social Systems Foundation. The purpose of this study was to establish a calibration system for clinical laboratory analyzers that are commonly used in Japanese laboratories, in order to promote the standardization of clinical tests. Standardization of an automatic calibration system for clinical laboratory analyzers will facilitate accuracy control without having to depend on the skill of laboratory operators, which will achieve the further standardization of clinical tests.

IFCC Guideline for sampling, measuring and reporting ionized magnesium in plasma

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.

Approved IFCC recommendation on reporting results for blood glucose: International Federation of Clinical Chemistry and Laboratory Medicine Scientific Division, Working Group on Selective Electrodes and Point-of-Care Testing (IFCC-SD-WG-SEPOCT)

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.

[Establishment of working reference materials in laboratory medicine]

It is recognized that the establishment of reference materials is the most important factor for standardization in laboratory medicine. In particular, working reference materials for routine measurement procedures are effective tools to maintain the commutability of measured values. Working reference materials are dealt with in a traceability chain system issued by ISO 17511 (in vitro diagnostic medical devices--measurement of quantities in biological samples--metrology traceability of values assigned to calibrators and control materials). The JCCLS is strongly promoting standardization in laboratory medicine by using working reference materials. Working groups for standardization are organized by the JCCLS in cooperation with the NMIJ (National Metrology Institute of Japan) with a grant from the NEDO (New Energy and Industrial Technology Development Organization). The objective is the establishment of working reference materials for routine use. Standardization criteria using the reference materials are being established. Research and development and investigation studies of matrix reference materials have been started. In investigation studies, the production protocol of reference materials are being prepared. After being established, reference materials will be presented to the JCTLM (Joint Committee on Traceability in Laboratory Medicine). These activities will enhance standardization in laboratory medicine. As a results, they will contribute to maintaining the reliability of measured values in routine laboratory procedures.

[Noninvasive blood glucose monitoring: new technology using metabolic heat conformation method]

Self-monitoring of blood glucose has become an essential aspect of management of patients with diabetes mellitus. Although several approaches for noninvasive blood glucose monitoring(NIGM) have been proposed including near infrared spectrophotometry. Body heat generated by glucose oxidation is based on the subtle balance of capillary glucose and oxygen supply to the cells. Hence, the blood glucose can be estimated by measuring the body heat and the oxygen supply. Development of the metabolic heat conformation (MHC) method consists of a sensor pickup and a calibration model. The calibration model incorporates mathematical procedures to process signals from the sensor pickup to final glucose value. The patients group was classified into clusters (calibration functions). Each subject patient was assigned to one of calibration functions. The assigned calibration function for the patient was later used for calculating the glucose values. Regression analysis involving 127 data points at random timing (109 data points from diabetic patients, 18 data points from non-diabetic patients) ranging 54mg/dl to 405mg/dl by the non-invasive method against the hexokinase photometric method for plasma as a reference method was performed. The correlation coefficient (r) was 0.91. Repeatability of the non-invasive method was measured for healthy fasting persons. The standard deviations were ranged from 5 to 6mg/dl around the concentration of 100mg/dl. These data provide preliminary evidence that the MHC method can be used to estimate blood glucose concentrations non-invasively.

Recommendation for measuring and reporting chloride by ISEs in undiluted serum, plasma or blood: International Federation of Clinical Chemistry and Laboratory Medicine (IFCC): IFCC Scientific Division, Committee on Point of Care Testing and Working Group on Selective Electrodes

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.

Approved IFCC recommendation on reporting results for blood glucose (abbreviated)

In current clinical practice, plasma and blood glucose are used interchangeably with a consequent risk of clinical misinterpretation. In human blood, glucose, like water, is distributed between erythrocytes and plasma. The molality of glucose (amount of glucose per unit of 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 calibrators, plasma, and erythrocyte fluid can explain some of the differences. Results of glucose measurements depend on sample type and on whether methods require sample dilution or use biosensors in undiluted samples. If the results are mixed up or used indiscriminately, the differences may exceed the maximum allowable error of glucose determinations for diagnosing and monitoring diabetes mellitus, and complicate the treatment. The goal of the IFCC 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 (with 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 the pertinent plasma. The conversion will provide harmonized results, facilitating the classification and care of patients and leading to fewer therapeutic misjudgments.

Japanese standard reference material for JDS Lot 2 haemoglobin A1c. I: Comparison of Japan Diabetes Society-assigned values to those obtained by the Japanese and USA domestic standardization programmes and by the International Federation of Clinical Chemistry reference laboratories

BACKGROUND

The Committee on Standardization of Laboratory Testing Related to Diabetes Mellitus of the Japan Diabetes Society (JDS) previously recommended use of the primary calibrator (JDS Lot 1) prepared by the former Committee for Standardization of Glycohemoglobin for standardizing the measurement of haemoglobin A1c (HbA1c). Owing to the depletion of vials of Lot 1 in March 2001, the present committee certified a new reference material, Lot 2, now distributed by the Health Care Technology Foundation (HECTEF). The standardization programme for HbA1c measurement in Japan is currently based on Lot 2, which has values assigned from within Lot 1; the Lot 1 values were consensus values based on assays by laboratories in the Japanese national quality control programme. In this study, for the purpose of international comparison and standardization, Lot 2 was assayed by the JDS reference laboratories, the National Glycoprotein Standardization Program (NGSP) in the USA, and by reference laboratories approved by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC).

METHOD

The HbA1c values of JDS Lot 2 were transferred from those assigned to Lot 1 using KO500, a high-resolution HPLC method, at three laboratories approved by the JDS committee. Subsequently, vials of JDS Lot 2 were shipped to and assayed by the NGSP in the USA and 10 IFCC reference laboratories.

RESULT

The JDS-assigned HbA1c values (from Lot 1) are 4.04 for Level 1, 5.38 for Level 2, 7.32 for Level 3, 9.88 for Level 4, and 12.63 for Level 5, all expressed as a percentage of total haemoglobin. The values obtained by NGSP and the IFCC laboratories gave the following formulas: NGSP value(%)=JDS value(%)+0.3%; IFCC value(%)=1.068xJDS value(%)-1.741%.

CONCLUSION

Although the values obtained by the IFCC laboratories are significantly lower than the values assigned to Lot 2 by the JDS, the relationship is linear. In addition, standardization of HbA1c based on JDS Lot 2 is currently at a satisfactory level in Japan. As a result, the reassignment of values for Lot 2 to agree with the IFCC values should be relatively easy and will be done after all relevant parties agree to the change.

[Procedure for accurate evaluation of laboratory data and its international trends]

From the work at ISO/TC212 (Clinical laboratory testing and in vitro diagnostic test systems), the international standards on medical laboratories--particular requirements for quality and competence and reference materials were issued. The accreditation of clinical laboratory was started using ISO 15189. Furthermore, on setting and usage of reference materials were constituted with compatibility global harmonization by newly organizing JCTLM (Joint Committee on Traceability in Laboratory Medicine). As the results, the work of the standardization based on reliability such as validation of reagent's kits and the measured values and uncertainty evaluation would be internationally advanced.

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

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.

Noninvasive Measurement of Glucose by Metabolic Heat Conformation Method

Background: We developed a method, called the metabolic heat conformation (MHC) method, for the noninvasive measurement of blood glucose. The MHC method involves the measurement of physiologic indices related to metabolic heat generation and local oxygen supply, which correspond to the glucose concentration in the local blood supply.

Methods: We used noninvasive thermal and optical sensors on the fingertip of an individual to measure thermal generation, blood flow rate, hemoglobin (Hb) concentration, and oxyhemoglobin concentration. The calibration model incorporates mathematical procedures to convert signals from the sensor pickup to final glucose concentrations. The mathematical procedures are multivariate statistical analyses, involving values from sensor signals, polynomials from various values, regression analyses of individual patients, and cluster analyses of patient groups. The glucose value is calculated for each patient measurement, applying one of the clusters by discriminant analysis.

Results: Regression analysis was performed to compare the noninvasive method with the hexokinase method, using 127 data points (109 data points from diabetic patients, 18 data points from nondiabetic patients) with glucose concentrations ranging from 3.0 to 22.5 mmol/L (54–405 mg/dL). The correlation coefficient (r) was 0.91. Reproducibility was measured for healthy fasting persons; the CV was 6% at 5.56 mmol/L (100 mg/dL).

Conclusions: These data provide preliminary evidence that the MHC method can be used to estimate blood glucose concentrations noninvasively.

[Laboratory accreditation and proficiency testing]

ISO/TC 212 covering clinical laboratory testing and in vitro diagnostic test systems will issue the international standard for medical laboratory quality and competence requirements, ISO 15189. This standard is based on the ISO/IEC 17025, general requirements for competence of testing and calibration laboratories and ISO 9001, quality management systems-requirements. Clinical laboratory services are essential to patient care and therefore should be available to meet the needs of all patients and clinical personnel responsible for human health care. If a laboratory seeks accreditation, it should select an accreditation body that operates according to this international standard and in a manner which takes into account the particular requirements of clinical laboratories. Proficiency testing should be available to evaluate the calibration laboratories and reference measurement laboratories in clinical medicine. Reference measurement procedures should be of precise and the analytical principle of measurement applied should ensure reliability. We should be prepared to establish a quality management system and proficiency testing in clinical laboratories.

Relationships of glucose concentrations in capillary whole blood, venous whole blood and venous plasma

We studied the difference in glucose levels between capillary and venous whole blood during 75-g oral glucose tolerance test (OGTT) in 75 healthy subjects. Capillary and venous whole blood glucose values were measured by HK-G6PD method after deproteinization. The post-loaded glucose levels in capillary blood were significantly higher than those in venous blood, and the mean values of capillary and venous difference at 30, 60, 90, 120 and 180 min were 1.37, 1.40, 1.07, 0.95 and 0.52 mmol/l, respectively, with the maximum difference at 60 min. No correlation was found in the magnitude of the differences in glucose between capillary and venous blood specimens. We determined the inaccuracy of six self-monitoring blood glucose devices relative to the reference method using venous plasma, venous whole blood and capillary whole blood from 31 diabetic patients. The differences of mean values of venous whole blood and capillary whole blood, and venous whole blood and venous plasma, and capillary whole blood and venous plasma were 9.6%, 11.3% and -3.2%, respectively. The range of bias and Sy/x were 0.31-1.06 mmol/l and 0.71-1.07 mmol/l, respectively, compared to the reference method using venous plasma.

[Blood glucose measurement]

For all diabetic patients in which the blood glucose is unstable, self-monitoring of blood glucose (SMBG) is effective. Especially, the patient who insulin supplies are necessary is indispensable SMBG in spite of tyep 1 and/or type 2 diabetes mellitus. SMBG measuring devices of looked forward nothing noninvasive type entered the practical stage. For example, the patient who requires the frequent measurement can be applied to alarms of the hypoglycemia unawareness, etc. from present performance, because blood glucose monitoring in the any time possible, though changing in taking in SMBG measuring device of the conventional invasive type, is not possible. And, it is possible to utilize in health care and protective measurement of the lifestyle related disease, etc., because the daily observation of the blood glucose is carried out in the long term. The function of data assist center, etc. is expected these this data for processing through the internet, etc. and follow of the result.

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.

Effects of a low dose leucovorin with 5-fluorouracil derivative on colorectal tumors induced with 1,2-dimethylhydrazine in rats

Thymidylate synthase, which is a key enzyme involved in the de novo pathway for pyrimidine nucleotide synthesis, is inhibited by 5-fluorodeoxyuridine monophosphate, forming an inactive ternary complex with intracellular folate. We investigated the effect of a 5-fluorouracil derivative (UFT) with or without low dose leucovorin on the number of 5-fluorodeoxyuridine monophosphate binding sites, thymidine kinase activity and intracellular folate concentration in 1,2-dimethylhydrazine-induced rat colorectal carcinomas. A 10-day administration of UFT with or without leucovorin enhanced the thymidine kinase activity and the number of 5-fluorodeoxyuridine monophosphate binding sites, with an increase of thymidylate synthase mRNA expression. Thymidylate synthase inhibition was slightly increased as the intracellular folate concentration increased. These results indicate that thymidylate synthase inhibition increases when the intracellular folate is exogenously supplemented and maintained at an adequate concentration.

Correlation between histological differentiation and DNA-synthesizing enzymes in rat colorectal tumors induced with 1, 2-dimethylhydrazine

Thymidylate synthase and thymidine kinase are key enzymes involved in de novo and salvage pathways for pyrimidine nucleotide synthesis. Colorectal carcinogenesis induced with 1,2-dimethylhydrazine in rats enhanced mRNA expression levels of both enzymes, resulting in the increase of both enzyme activities and bromodeoxyuridine-immunoreactive S-phase cells. Poorly and well differentiated adenocarcinomas of the colorectum showed the relative elevation of activities of thymidylate synthase and thymidine kinase, respectively. These results indicate that the relationship between de novo and salvage pathways for pyrimidine nucleotide synthesis may depend on the histopathological grades of cell differentiation.

Effects of long-term administration of UFT plus leucovorin on colorectal tumors induced with 1,2-dimethylhydrazine in rats

Thymidylate synthase and thymidine kinase are key enzymes involved in the de novo and salvage pathways for pyrimidine nucleotide synthesis, respectively. Thymidylate synthase is inhibited by 5-fluorodeoxyuridine monophosphate, forming an inactive ternary complex with intracellular folate. We investigated the effects of 1-(2-tetrahydrofuryl)-5-FU plus uracil (UFT) with or without leucovorin on 1,2-dimethylhydrazine-induced rat colorectal carcinomas. Thirty-week administration of UFT with or without leucovorin markedly suppressed both colorectal carcinogenesis and tumor growth, resulted in the increase of thymidylate synthase inhibition and the decrease of thymidine kinase activity in the tumor cells. These results indicate that the combination of UFT with leucovorin could be useful in the development of pre- and post-operative adjuvant chemotherapy programs.

Serum des-gamma-carboxy prothrombin levels determined by a new generation of sensitive immunoassays in patients with small-sized hepatocellular carcinoma

OBJECTIVE

Des-gamma-carboxy prothrombin (DCP), also called protein induced by vitamin K absence or antagonist II (PIVKA-II), is a tumor marker complementary to AFP for the diagnosis of hepatocellular carcinoma (HCC). Currently available immunoassays for DCP are not sensitive enough to detect HCC at an early stage. Recently, two new immunoassays with enhanced sensitivity were developed. The aim of this study was to assess the diagnostic values of the new methods in patients with small-sized HCC.

METHODS

Coded serum samples obtained from 36 patients with small-sized and single-nodular HCC (< or = 3 cm in diameter) and 49 patients with posthepatitic cirrhosis not carrying HCC were analyzed. DCP levels were determined in three different ways: 1) conventional EIA; 2) a new immunoassay using the electrochemiluminescence (ECLIA) detection system; and 3) a new immunoradiometric assay (IRMA). Lectin-reactive profiles of AFP (AFP-L3) were also determined.

RESULTS

In 36 patients with small-sized HCC, the rates of abnormal values obtained by the conventional, ECLIA, and IRMA methods were 2.7%, 27.8%, and 16.7%, respectively. An ROC analysis of the two new methods (ECLIA vs IRMA) revealed a better performance by the ECLIA method (p < 0.05). The true positive rate of AFP-L3 was 22.2%, whereas a combination assay of ECLIA for DCP and AFP-L3 resulted in a 41.7% sensitivity with a specificity of 90%.

CONCLUSIONS

Compared with the conventional method, the sensitivity in detecting small-sized HCC was increased in the two new DCP immunoassays (ECLIA and IRMA). The overall performance as evaluated by an ROC analysis was significantly better in ECLIA than in IRMA.

Effects of 5-fluorouracil derivative UFT on thymidylate synthetase and thymidine kinase in rat colorectal tumors

BACKGROUND

Thymidylate synthetase and thymidine kinase are key enzymes involved in de novo and salvage pathways for pyrimidine nucleotide synthesis, respectively.

MATERIALS AND METHODS

Weekly injections of 1,2-dimethyl-hydrazine induced high incidence of colorectal adenocarcinomas in rats.

RESULTS

An increased activity of thymidylate synthetase was found in the poorly differentiated adenocarcinomas of the chemically induced rat colorectal tumors. Six-week oral administration of 1-(2-tetrahydrofuryl)-5-fluorouracil in combination with uracil (UFT) reduced the total number of colorectal tumors, with the reduction of thymidylate synthetase activity in the poorly-differentiated type, though the mRNA expression of thymidylate synthetase and thymidine kinase differed little between the groups with or without UFT treatment.

CONCLUSIONS

These results indicate that the long-term oral administration using UFT suppresses colorectal carcinogenesis and the growth of the poorly-differentiated type tumors.

Additive effects of medroxyprogesterone acetate and 5-fluorouracil derivative on 7,12-dimethylbenz[a]anthracene-induced rat mammary tumors

Chronic oral administration of 1-(2-tetrahydrofuryl)-5-fluorouracil in combination with uracil suppressed thymidylate synthetase (TS) gene expression followed by reduction of TS activity in rat mammary tumors induced with 7,12-dimethylbenz[a]anthracene. Addition of medroxyprogesterone acetate (MPA) to the anticancer drug caused an additional decrease in TS and thymidine kinase activities in the tumor growth and restoration of bone loss. These results suggest that the simultaneous administration of MPA and anticancer drugs causes increased inhibition of mammary tumor growth and also diminishes the bone loss.

Effects of tamoxifen on mammary tumors and bone in 7,12-dimethylbenz-(a)anthracene-treated rats

We investigated the effects of tamoxifen on the growth of 7,12-dimethylbenz(a)anthracene induced rat mammary tumors, the activity of thymidylate synthetase and thymidine kinase (key enzymes involved in de novo and salvage pathways for pyrimidine nucleotide synthesis), and also their gene expression. The effects on immunohistochemistry using bromodeoxyuridine in the tumors and bone mineral density of the femur in rats were also studied. Chronic administration of tamoxifen markedly reduced the expression of thymidylate synthetase mRNA, followed by a reduction in enzyme activity and S-phase cells in the mammary tumors, and significantly enhanced the bone mineral density. Tamoxifen not only attenuated bone loss in aging but also enhanced bone volume in mammary tumor-bearing rats in which tumor growth was suppressed via both the de novo and salvage pathways for pyrimidine nucleotide synthesis.

Additional effects of medroxyprogesterone acetate on mammary tumors in oophorectomized, estrogenized, DMBA-treated rats

Although hormone replacement therapy not only relieves vasomotor symptoms but also reduces cardiovascular disease and osteoporosis, long-term estrogen therapy increases the risk of endometrial and/or mammary cancer. We investigated the effects of conjugated estrogens with or without medroxyprogesterone acetate in oophorectomized, 7,12-dimethylbenz(a)anthracene-treated rats. Chemically induced mammary carcinogenesis was completely suppressed by the simultaneous oophorectomy, but conjugated estrogens replacement with or without medroxyprogesterone acetate markedly stimulated mammary carcinogenesis in the ovariectomized rats. The chronic administration of conjugated estrogens and medroxyprogesterone acetate markedly reduced the activities of thymidylate synthetase and thymidine kinase and bromodeoxyuridine-immunoreactive (S-phase) cells in mammary tumors. These results indicate that the treatment using conjugated estrogens with or without medroxyprogesterone acetate may promote the mammary carcinogenesis in postmenopausal women but the chronic administration of medroxyprogesterone acetate may alter the development of established mammary cancer.

Effects of macrophage- and granulocyte-colony stimulating factors on thymidylate synthase and thymidine kinase activity in rat hematopoietic cells

The effects of macrophage (M) and granulocyte (G) colony-stimulating factors (CSFs) on the activity of thymidylate synthase and thymidine kinase, which are involved in de novo and salvage pathways for pyrimidine nucleotide synthesis, were investigated in the hematopoietic cells of rats treated with cyclophasphamide. Thymidine kinase activity, but not that of thymidylate synthase, was markedly enhanced in these cells by M- and G-CSF treatment (p < 0.05 and p < 0.01). G-CSF directly, and M-CSF indirectly stimulate myeloid cells and lead to S-phase predominantly via the salvage pathway for pyrimidine nucleotide synthesis. The present study indicates that these CSFs can be effective inducers of complete remission in acute leukemias when employed together with chemotherapy.

Effects of a new clerodane diterpenoid isolated from propolis on chemically induced skin tumors in mice

Propolis is a resinous material gathered by honey bees from the buds and bark of certain trees and plants, and used inside their hives. Characteristic components of propolis are many kinds of flavonoid aglycones. The methanol extract of a Brazilian propolis was fractionated by HPLC, and a tumoricidal substance was isolated and characterized as a new clerodane diterpenoid (PMS-1) with a molecular formula of C20H32O3 (MW: 320). We investigated the effects of PMS-1 on skin tumorigenesis and the development of skin tumors induced by 7,12-dimethylbenz(a)anthracene application on mouse back skin. It was tentatively concluded that PMS-1 reduced the incidence of skin tumors by inhibition of DNA synthesis in a de novo pathway, and suppressed the growth of the tumors by decreasing DNA synthesis in a salvage pathway.

Effects of estrone with or without medroxyprogesterone acetate on the femur in aged rats

In an attempt to define the efficacy of hormone replacement therapy in postmenopausal osteoporosis, we investigated the effects of estrone with or without medroxyprogesterone acetate on the bone mineral density of the femur of aged rats, of which plasma levels of luteinizing hormone (LH), follicle stimulating hormone (FSH) and estradiol were markedly reduced in comparison with those of younger rats. Although additional sex hormones had little effect on the plasma levels of gonadotropins, chronic administration of estrone significantly enhanced the bone mineral density of femur in aged animals.

Serum thymidine kinase as a tumor marker of colorectal carcinogenesis induced with 1,2-dimethylhydrazine in rats

Thymidine kinase is the key enzyme in salvage pathway for pyrimidine nucleotide synthesis. High activities of thymidine kinase have been found in rapidly proliferating normal, neoplastic tissues and sera from patients with various diseases including lymphoma, leukemias and small cell lung cancer. We investigated the serum thymidine kinase activities and the colorectal carcinomas in rats treated with 1,2-dimethylhydrazine. The positive correlations between serum thymidine kinase activities and numbers of total and large tumors were observed. These findings suggest the measurement of serum thymidine kinase activity may be clinically valuable in an early stage of the colonic carcinogenesis.

Accuracy evaluation and hematocrit effect of commercial ionized calcium analyzers using Japanese serum reference material

The serum reference material for concentration measurement of ionized calcium in blood has been established by our research group in Japan. The reference method used is the reference standard cell (RSC:IFCC/WGSE, Covington-Umemoto Cell) system. Here we present the results of the evaluation of accuracy using the serum reference material and the hematocrit effect of the nine commercial ionized calcium analyzers being used in routine measurements by Japanese round robin test program. The ionized calcium concentration and pH of two concentration levels of the reference material were analyzed in triplicate measurements according to the standard procedures designated by manufacturers. The effect of hematocrit in ionized calcium concentration measurement was tested using plasma and whole blood with hematocrit values of 35%, 50% and 65%, respectively. The range of bias of ionized calcium values were -0.14 approximately +0.09 mmol/L, -0.12 approximately +0.09 mmol/L for ionized calcium, respectively. The effect of hematocrit in ionized calcium concentration measurement was strongly observed in GEM Premier, CAI-101 and GASTAT-2 analyzers.

[Calibration and standardization in enzyme immunoassay]

Calibration is performed using multipoints of the calibrator in enzyme immunoassay (EIA). Calibration curves in EIA are frequently represented by non-linearity. Therefore, calibration in EIA is fitted with suitable functions. These functions are demonstrated with logistic curve, logit-log conversion, spleen function, etc. Consequently, the calibration procedure is indicated for the manufacturer's instruction, and also the calibrator is prepared as a commercial available reagent kit. To minimize EIA measurements among laboratories, and among methods, standardization with a common suitable reference material is needed. Reference materials for EIA, international standards are prepared by the expert committee of WHO. These standards must be transferred to national standards, manufacturer's standards and calibrators of commercial available reagent kits. Finally, the measured value from the routine method is maintained with commutability and traceability.

Effects of danazol on thrombopoiesis in rats

A synthetic analog of ethinyltestosterone, Danazol, has been used clinically for the treatment of immune thrombocytopenia. We investigated the effects of Danazol on thrombopoiesis in normal rats. Though 4-week treatment by Danazol slightly enhanced the DNA synthesizing enzyme activities and the number of S-phase cells in bone marrow and spleen, the number of megakaryocytes and thrombocytes were not increased in bone marrow and peripheral blood, respectively. These findings suggest that Danazol treatment will not induce thrombosis with thrombocytosis in normal human beings and animals.

Effects of Chinese herbal medicines on DNA-synthesizing enzyme activities in mammary tumors of mice

Sho-saiko-to (SST) and Juzen-taiho-to (JTT), Japanese modified Chinese herbal prescriptions, suppressed the activities of thymidylate synthetase and thymidine kinase involved in de novo and salvage pathways for pyrimidine nucleotide synthesis, respectively, in mammary tumors of SHN mice with the reduction of serum prolactin level. These results indicate that SST and JTT may have the antitumor effects on mammary tumors.