Standardization of Laboratory Data and Establishment of Reference Intervals in the Fukuoka Prefecture: A Japanese Perspective

Comparative evaluation of methods to determine intra-individual reference ranges in nutrition support team (NST)-related tests

BACKGROUND

The intra-individual reference range is generally narrower than the commonly used reference range. Consequently, close monitoring of changes in the laboratory test results of individuals based on the inter-individual reference range remains challenging.

METHODS

We examined the determination of individual reference ranges using four indicators of nutritional conditions: transferrin (TRF), albumin (ALB), retinol-binding protein (RBP), and transthyretin (TTR). The subjects comprised 20 healthy individuals and blood samples were collected and tested five times at 2-week intervals. We used the measurement results for the four indicators and examined individual reference ranges using four methods, including calculation methods based on the reference change value and Bayesian inference.

RESULTS

The resulting intra-individual reference ranges were narrower than the currently used inter-individual reference range for all measurements using four methods. Furthermore, the intra-individual coefficient of variation [CV (intra)] was smaller than the inter-individual coefficient of variation [CV (inter)] for TRF, RBP, and TTR for all 20 subjects. The means CV (intra) for the four indicators were also lower than the corresponding CV (inter).

CONCLUSIONS

The intra-individual reference range can be used to validate the standard deviation and coefficient of variation for currently used indicators. Moreover, Bayesian methods are speculated to be the most versatile.

Blood Reference Intervals for Preterm Low-Birth-Weight Infants: A Multicenter Cohort Study in Japan

Preterm low-birth-weight infants remain difficult to manage based on adequate laboratory tests. The aim of this study was to establish blood reference intervals (RIs) in those newborns who were admitted to and survived in the neonatal intensive care unit (NICU). A multicenter prospective study was conducted among all infants admitted to 11 affiliated NICUs from 2010 to 2013. The clinical information and laboratory data were registered in a network database designed for this study. The RIs for 26 items were derived using the parametric method after applying the latent abnormal values exclusion method. The influence of birth weight (BW) and gestational age (GA) on the test results was expressed in terms of the standard deviation ratio (SDR), as SDR_BW and SDR_GA, respectively. A total of 3189 infants were admitted during the study period; 246 were excluded due to a lack of blood sampling data, and 234 were excluded for chromosomal abnormalities (n = 108), congenital anomalies requiring treatment with surgical procedures (n = 76), and death or transfer to another hospital (n = 50). As a result, 2709 infants were enrolled in this study. Both the SDR_GA and SDR_BW were above 0.4 in the test results for total protein (TP), albumin (ALB), alanine aminotransferase (ALT), and red blood cells (RBC); their values increased in proportion to the BW and GA. We derived 26 blood RIs for infants who were admitted to NICUs. These RIs should help in the performance of proper clinical assessments and research in the field of perinatal-neonatal medicine.

Multianalyte Conventional Reference Material (MacRM): A Useful Tool for Nationwide Standardization of Laboratory Measurements for Medical Care—A Model Study in Japan

BACKGROUND

The Japanese Committee for Clinical Laboratory Standards (JCCLS) has developed a multianalyte conventional reference material (MacRM) for nationwide standardization of laboratory measurements.

METHODS

To prepare the MacRM, pooled sera were obtained from healthy Japanese individuals. Target values of the pooled sera for 30 analytes were assigned on the basis of the measurement results of 45 certified clinical laboratories whose calibration was verified by measuring certified reference materials (CRMs) provided by the National Institute of Standards and Technology, the Institute for Reference Materials and Measurements, and JCCLS. Commutability of MacRM was assessed by comparison with results for 150 individual inpatients at Fukuoka University Chikushi Hospital. Survey samples were prepared by essentially the same method for MacRM but without target values. The survey samples were used to assess agreement among 165 laboratories that used various assay kits and platforms calibrated with the MacRM.

RESULTS

The commutability of MacRM was confirmed for 30 analytes with sera from 150 individual patients. The imprecision (CV) of measurements of survey samples (high and low concentrations) among the 165 laboratories was 0.4%–10.0%. Twenty-six of 30 analytes were within the goals for interinstitutional allowable bias. An aliquot of MacRM stored frozen at −80 °C remained stable for ≥4 years.

CONCLUSIONS

The MacRM was successfully applied as a calibrator to achieve nationwide standardization for 30 analytes measured by 165 laboratories that used various methods from different manufacturers.

Significance of preoperative butyrylcholinesterase as an independent predictor of biochemical recurrence-free survival in patients with prostate cancer treated with radical prostatectomy

BACKGROUND

Butyrylcholinesterase (BChE) is an alpha-glycoprotein found in the nervous system and liver. Its serum level is reduced in many clinical conditions, such as liver damage, inflammation, injury, infection, malnutrition, and malignant disease. In this study, we analyzed the potential prognostic significance of preoperative BChE levels in patients with prostate cancer (PCa) undergoing radical prostatectomy (RP).

METHODS

We retrospectively evaluated 535 patients with PCa who underwent RP from 1996-2014 at a single institution. Serum BChE was routinely measured in all patients before operation. Covariates included age, preoperative laboratory data [prostate-specific antigen (PSA), hemoglobin, total protein, albumin, BChE, lactate dehydrogenase, C-reactive protein], clinical T, biopsy Gleason score, D'Amico risk classification, and RP with/without neoadjuvant therapy. Univariate and multivariate analyses were performed to identify clinical factors associated with biochemical recurrence-free survival (BRFS). Univariate analyses were performed using the Kaplan-Meier and log-rank methods, and multivariate analysis was performed using a Cox proportional hazard model.

RESULTS

The median BChE level was 255 U/L (normal range 168-470 U/L). The median age of the enrolled patients was 68 years, and the median PSA level at diagnosis of PCa was 8.39 ng/mL. The median follow-up period was 65 months. The 5-year BRFS rate was 72.9 %. The 5-year BRFS rates in the BChE ≥ 168 and ≤ 167 U/L groups were 77.7 and 55.0 %, respectively (P < 0.001). In univariate analysis, BChE, cT, biopsy Gleason score, and D'Amico risk classification were significantly associated with BRFS. Multivariate analysis revealed that BChE was significantly associated with BRFS.

CONCLUSIONS

This study validated preoperative serum BChE levels as an independent prognostic factor for PCa after RP.

Preliminary evaluation of an improved enzymatic assay method for measuring potassium concentrations in serum

BACKGROUND

K(+) has important physiological functions. K(+) concentrations in serum are generally determined using ion-selective electrodes (ISEs), though measurement using reagents in aqueous medium is also useful.

METHODS

K(+) concentrations were measured using recombinant inosine 5'-monophosphate dehydrogenase (IMPDH), which was activated only by K(+) and NH4(+). Exogenous NH4(+) and endogenous NH4(+) were eliminated using glutamine synthase.

RESULTS

Regression analysis of the enzymatic assay (y) vs. the ISE method (x) gave the following relation: y=1.03x+0.09 (n=54, Sy,x=0.06 mmol/l). The linear range was up to 12 mmol/l when 1 U/ml IMPDH was used.

CONCLUSION

Advantages of the proposed assay method are: (i) the measured range is wider than that of existing enzymatic methods; (ii) the conditions for K(+) determination can be maintained constant, regardless of the amount of NH4(+) in the analyte and reagents; and (iii) the elimination system is simpler because the recombinant IMPDH is stimulated by only K(+) and NH4(+) and is unaffected by biological materials.

Nationwide multicenter study aimed at the establishment of common reference intervals for standardized clinical laboratory tests in Japan

BACKGROUND

The Japanese Association of Medical Technologists (JAMT) sought to establish common reference intervals (RIs) applicable nationwide in Japan for 27 serum constituent analytes for which certified reference materials are available and nine analytes frequently measured in routine tests. More than 100 laboratories certified for metrological traceability collaborated in the recruitment, sampling, and measurement of analytes for the establishment of RIs. No previous attempt has been made to establish RIs by such a large number of laboratories. The allowable limits of trueness and intermediate precision based on the JAMT criteria were applied to the reference values measured by these laboratories, and measured values within the allowance limits were used to establish RIs.

METHODS

Reference individuals included 5748 healthy volunteers aged 18-65 years who were engaged in medical care-related work based on the CLSI guidelines. After secondary exclusion of individuals in whom abnormal values were detected in basic routine test items and adjustment for the distribution of age and gender, 3371 reference individuals were chosen in the parametric determination of RIs. Employing the three-level nested ANOVA, between-laboratory, -region, -sex, and -age variations were evaluated.

RESULTS

No significant difference was noted in between-region variations in any item. Results of ANOVA revealed between-sex and -age variations in 14 and 15 analytes, respectively. Based on these results of variation, RIs were established with and without partition by sex.

CONCLUSIONS

Since no between-region variation was detected in reference values among accuracy-certified core laboratories, RIs applicable nationwide were established.

Upper limit of normal serum alanine and aspartate aminotransferase levels in Korea

BACKGROUND AND AIM

 The widely accepted range of upper limits of normal (ULN) alanine aminotransferase (ALT) levels (ULN < 40 U/L) was recently challenged by several reports. Both ALT and aspartate aminotransferase (AST) are commonly used as surrogate markers of liver disease, but almost all studies of aminotransferase activity were conducted on ALT. We investigated not only ULN of ALT but also AST activity and to identify factors modulating them in healthy Korean.

METHODS

A cross-sectional study of 411,240 registered blood donors in all nationwide blood banks belonging to the Korean Red Cross were conducted. ULN of ALT and AST was evaluated adjusting their age according to the national population census database. "Decision tree model" was used to identify the affecting factors of ALT and AST and optimal cut-off points of affecting factors.

RESULTS

 "ULN of ALT" was 34 U/L in men and 24 U/L in women and "ULN of AST" was 32 U/L in men and 26 U/L in women in the blood donor database. Decision tree analysis showed that ALT levels were mostly influenced by body mass index level and its critical two cut-off points were 23.5 kg/m2 and 25.8 kg/m2 , respectively. The most affecting factor of AST was gender.

CONCLUSION

Upper limits of normal of ALT and AST in Koreans were lower than conventional accepted values (< 40 U/L) but higher than recently suggested values (male < 30 U/L and female < 19 U/L). Body mass index was the most determining factor for ALT and gender was the most influencing factor for AST activity.

Combined effects of coffee consumption and serum γ-glutamyltransferase on serum C-reactive protein in middle-aged and elderly Japanese men and women

BACKGROUND

The association between coffee intake and circulating levels of C-reactive protein (CRP) may be modified by oxidative stress. The authors examined the relation of coffee consumption to serum CRP considering potential inter-actions of serum γ-glutamyltransferase (GGT) and bilirubin.

METHODS

The subjects included 4455 men and 5942 women aged 49-76 years who participated in the baseline survey of a cohort study on lifestyle-related diseases in Fukuoka, Japan. Geometric means of serum CRP and 95% confidence intervals across the category of coffee intake stratified by serum GGT and bilirubin were estimated using multiple linear regression.

RESULTS

Serum CRP concentrations were progressively lower with higher intake of coffee in men with high serum GGT (p for trend=0.009), but not in those with low serum GGT (p for trend=0.73) and GGT modified the association (p for interaction=0.03). Women showed no association between coffee intake and CRP whether serum GGT was low or high. There was no effect modification of serum bilirubin on the association between coffee intake and CRP in either men or women.

CONCLUSIONS

These results support a protective effect of coffee intake against systematic inflammation in middle-aged and elderly Japanese men and imply that such an effect may be stronger in elevated oxidative stress.

Relation of coffee consumption and serum liver enzymes in Japanese men and women with reference to effect modification of alcohol use and body mass index

OBJECTIVE

Previous studies have shown that coffee consumption is inversely related to serum levels of liver enzymes such as alanine aminotransferase (ALT), aspartate aminotransferase (AST), and gamma-glutamyl transferase (GGT), but few have addressed the relation in women and effect modifications of alcohol use and obesity. We examined the association of coffee and green tea consumption with serum activities of liver enzymes in free-living Japanese men and women, focusing on sex difference and effect modifications of alcohol and obesity.

MATERIAL AND METHODS

The data were derived from the baseline survey of the Kyushu University Fukuoka Cohort Study, and included 12,020 Japanese men and women aged 49-76 years who were free of chronic liver diseases.

RESULTS

There was an inverse association between coffee consumption and elevated ALT in men, and the association between the two was weaker in women. In the analyses stratified by aminotransferases category, inverse associations of coffee consumption with serum activities of liver enzymes were observed in both men and women within the whole range and among those with aminotransferases within the reference range (ALT/AST <or=40 IU/L for men and ALT/AST <or=30 IU/L for women). Inverse associations of coffee with liver enzymes were more evident in those with high alcohol consumption and in those with low body mass index.

CONCLUSIONS

Coffee drinking probably confers protection against alcohol-related increase in liver enzymes.

The relation of coffee consumption to serum uric Acid in Japanese men and women aged 49-76 years

Objective. Few studies have suggested an inverse relation between coffee intake and serum concentrations of uric acid (UA), but none has addressed the relation in men and women separately. We examined the relation between coffee intake and serum UA levels in free-living middle-aged and elderly men and women in Fukuoka, Japan. Methods. Study subjects were derived from the baseline survey of a cohort study on lifestyle-related diseases, and included 11.662 men and women aged 49–76 years; excluded were those with medication for gout and hyperuricemia, use of diuretic drugs, and medical care for cancer or chronic kidney disease. Statistical adjustment was made for body mass index, alcohol use, hypertension, diabetes mellitus, and other factors. Results. There were inverse associations of coffee consumption with serum UA concentrations and hyperuricemia in men regardless of adjustment for covariates. Women showed a statistically significant, but weaker, inverse association between coffee and serum UA levels after allowance for the confounding factors. Conclusion. The findings add to evidence for a protective association between coffee intake and hyperuricemia.

Prerequisites for establishing common reference intervals

Establishment of common reference intervals for homogeneous populations within regions is based on the same basic principles as the IFCC recommendations for individual laboratories, but a few additional prerequisites are needed. Thus, the need for common standardization and traceability during production of the reference values and with the application of the common reference intervals in the laboratories becomes crucial. Furthermore, the external control system must be geared to the purpose, using matrix-correct control materials with concentration values traceable to the same reference methods, and validation of results according to analytical quality specifications designed for the use of common reference intervals. Here, the standards may have a restrictive influence on the establishing of common reference intervals, with their demands for the use of the producers' traceability, instead of a relevant high-quality reference preparation shared by all the participants. Two main strategies for measurements are analysis immediately after the sampling, and storage of samples until analysis in one or a few analytical runs. The former strategy needs constant standardization and stability of the performance in many laboratories and in several analytical runs, resulting in between-run variation, whereas the latter precludes this between-run variation, but makes demands on the stability of the components under storage. When a considerable number of laboratories decide to establish common reference intervals, it is possible to obtain large sample sizes of reference values, which reduces the confidence intervals around the reference limits. It also makes it possible to collect samples from many subgroups, such as racial groups and groups related to different environmental conditions, as well as the traditional groupings according to age and gender, pregnancy and use of oestrogens. If all these subgroups are large, e.g. n>500, the confidence limits will be small and criteria for partitioning can be applied. Choosing reference individuals is not easy, as definitions of health, as well as rule-in and rule-out criteria vary from one investigation to the other. Therefore, the strategy and the criteria must be thoroughly described. Arguments for establishing common reference intervals are not needed. On the contrary, lack of such common reference intervals should be explained.

Managing transferability of laboratory data

Considerable attention has been focused on definition and enhancement of the analytical quality in laboratory testing over the past decades. Advances in laboratory technology and computer informatics have allowed a major sense of confidence with the analytical phase and more efforts should now be focused on extra-analytical areas of improvement, that should further strengthen the link between cost effectiveness and clinical outcome. Deduction and implementation of common reference intervals, to be possibly shared by a regional network of clinical laboratories, appear so far a crucial step to increase efficiency and harmonization. With the experience gained from External Quality Control exercises and with the consensus of several contributory laboratories, this process is underway in Italy. Quality performances resulting from widespread implementation of common reference intervals and longitudinal comparison of patient's data, will allow clinical laboratories to accomplish with a major transferability, amplifying health benefits and meeting increasing health systems demand.

Protein S and protein C gene mutations in Japanese deep vein thrombosis patients

OBJECTIVES

Coagulation factor V Leiden has not been detected in Japanese patients suffering from thrombosis. Hitherto, the constitutional background of Japanese thrombotic patients has never been systematically examined. We have performed a systematic investigation to determine pathogenesis for deep vein thrombosis in a Japanese population.

DESIGN AND METHODS

Routine coagulation and fibrinolysis tests were performed to determine the activities of protein S, protein C, antithrombin, plasminogen and fibrinogen. Gene analysis was performed in thrombotic patients having low activities of these factors.

RESULTS

Our study indicates that the frequency (19/85 = 0.22) of mutations of protein S gene in the Japanese patients was 5-10 times higher than that of mutations of protein S gene in Caucasian patients, and the frequency (8/85 = 0.09) of mutations of protein C gene was almost three times higher than that of Caucasian patients. The frequency of antithrombin gene mutation was similar in both populations.

CONCLUSION

Our study reinforces that the genetic anomaly in the protein S/protein C anticoagulation system is an important risk factor for thrombophilia in the Japanese population.

Analytical goals for coagulation tests based on biological variation

Allowable imprecision and bias reference limits for laboratory data can be calculated based on measurements of biological variation. Although biological variation of clinical chemical data has been reported from many laboratories, there have been few reports of biological variation in coagulation tests. In this study, we calculated the biological variation of 13 coagulation tests in the clinical laboratory of Kyushu University Hospital and determined allowable imprecision and bias limits of variation. The participating subjects were 17 healthy individuals: three males and two females in their 20s, two males and two females in their 30s, one male and four females in their 40s, and two males and one female in their 50s. Monthly measurements were performed before breakfast 12 times from June 2001 to May 2002 and allowable imprecision and bias limits were calculated. Taken together with coefficient of variation of control plasma used in daily laboratory work at the hospital, the allowable imprecision limits of intra-laboratory variation determined in this study appear to be in attainable ranges.

Standardization of immunoassay for CRM-related proteins in Japan: from evaluating CRM 470 to setting reference intervals

The Japan National Institute of Health (JNIH), in close collaboration with academic societies, commercial companies, and the Japan Society of Medical Technologists, has led in the attempt to standardize plasma protein assays since the mid 1980s. Under a framework of global standardization, they used WHO primary reference materials to reduce discrepancies in values reported for proteins assayed using different systems, thus laying the foundations for a protein immunoassay standardization system in Japan. With the introduction of CRM 470 in 1993, the Japanese Committee for Clinical Laboratory Standards (JCCLS) has taken the initiative in promoting the use of the new material and bringing about the re-evaluation of all systems of quality assurance in clinical laboratories. This eventually led to the establishment of reference intervals in Japanese populations of children and adults after preparation of assigned calibrators from CRM 470 for each assay system. Here we review the history of a series of projects carried out in Japan and describe several remaining problems, through which we will attempt to evaluate the potential value of protein immunoassay standardization.