Reference intervals for 33 biochemical analytes in healthy Indian population: C-RIDL IFCC initiative

A preliminary study on the reference intervals of serum tumor marker in apparently healthy elderly population in southwestern China using real-world data

BACKGROUND

The aim is to establish and verify reference intervals (RIs) for serum tumor markers for an apparently healthy elderly population in Southwestern China using an indirect method.

METHODS

Data from 35,635 apparently healthy elderly individuals aged 60 years and above were obtained in West China Hospital from April 2020 to December 2021. We utilized the Box-Cox conversion combined with the Tukey method to normalize the data and eliminate outliers. Subgroups are divided according to gender and age to examine the division of RIs. The Z-test was used to compare differences between groups, and 95% distribution RIs were calculated using a nonparametric method.

RESULTS

In the study, we observed that the RIs for serum ferritin and Des-γ-carboxy prothrombin (DCP) were wider for men, ranging from 64.18 to 865.80 ng/ml and 14.00 to 33.00 mAU/ml, respectively, compared to women, whose ranges were 52.58 to 585.88 ng/ml and 13.00 to 29.00 mAU/ml. For other biomarkers, the overall RIs were established as follows: alpha-fetoprotein (AFP) 0-6.75 ng/ml, carcinoembryonic antigen (CEA) 0-4.85 ng/ml, carbohydrate antigen15-3 (CA15-3) for females 0-22.00 U/ml, carbohydrate antigen19-9 (CA19-9) 0-28.10 U/ml, carbohydrate antigen125 (CA125) 0-20.96 U/ml, cytokeratin 19 fragment (CYFRA21-1) 0-4.66 U/ml, neuron-specific enolase (NSE) 0-19.41 ng/ml, total and free prostate-specific antigens (tPSA and fPSA) for males 0-5.26 ng/ml and 0-1.09 ng/ml. The RIs for all these biomarkers have been validated through our rigorous processes.

CONCLUSION

This study preliminarily established 95% RIs for an apparently healthy elderly population in Southwestern China. Using real-world data and an indirect method, simple and reliable RIs for an elderly population can be both established and verified, which are suitable for application in various clinical laboratories.

Establishment of reference intervals for free light chains and immunoglobulins in Saudi population

OBJECTIVES

Testing of serum-free light chains kappa (κ) and lambda (λ), along with ratio (FLCR) is essential for the diagnosis and management of monoclonal gammopathies. Accurate clinical diagnosis depends upon appropriate local population reference intervals (RIs). This study examined the Saudi population for serum-free light chains and other immunoglobulins to establish RIs and to explore variations in the test results by using the International Federation for Clinical Chemistry and Laboratory Medicine's global protocol for harmonized implementation of RI study.

METHODS

A total of 180 healthy Saudi adults were recruited. All serum samples were assayed using the Freelite reagents from the Binding Site. The variation in reference values attributable to sex, age, BMI, and region was calculated by ANOVA as a standard deviation ratio (SDR). The RIs for the FLCR were derived by the parametric method and validated by using samples from patients with hypo- and hypergammaglobulinemia.

RESULTS

The new RIs for free κ and FLCR were shifted to a higher side from the manufacturer-adapted RIs. Based on the SDR cutoff value (>0.4), between-sex partition RIs were not required for all analytes except IgM. Validation using patients with hypo- or hypergammaglobulinemia and without multiple myeloma, was all within the new RI. BMI, smoking, and exercise were not relevant sources of variation for any analyte.

CONCLUSIONS

Locally derived RIs for free light chains and immunoglobulins analytes specific for Saudis were established after careful consideration of various factors. These RIs were more reliable than those provided as guidance by the manufacturer, or from other countries, for appropriate classification and prediction of disease progression for Saudi patients.

Reference intervals of biochemical parameters in Chilean adults

Background

Establishing reference intervals (RIs) in clinical laboratories is essential, as these can vary due to inter-individual variability as well as the analytical methods used. The purpose of this study was to determine RIs for markers and ratios biochemical in apparently healthy Chilean adults.

Methods

A sample of 1,143 data was selected from the Universidad Católica de Temuco, Clinical Laboratory database, La Araucanía Region, Chile, which were analysed by sex. The Tukey's Fences was used to detect outliers and the RIs were established using the non-parametric method.

Reference Interval for Non-HDL-Cholesterol, Remnant Cholesterol and Other Lipid Parameters in the Southern Iranian Population; Findings From Bandare Kong and Fasa Cohort Studies

BACKGROUND

Growing evidence shows the undisputable role of non-HDL-C and remnant cholesterol (remnant-C) in cardiovascular disease (CVD) risk assessment and treatment. However, the reference interval (RI) for these lipid parameters is not readily available. The aim of the present investigation was to determine the age and sex-specific RIs for non-HDL-C and remnant-C as well as other lipid parameters among a healthy population in southern Iran. We also report the RI of lipid parameters in rural and urban residents, smokers and post-menopausal women.

METHODS

Among 14063 participants of Bandare Kong and Fasa cohort studies, 792 healthy subjects (205 men and 578 women) aged 35-70 years were selected. Fasting blood samples were used for determination of total cholesterol (TC), triglycerides (TG) and HDL-C using colorimetric methods. Non-HDL-C and remnant-C were calculated using the valid formula. The 2.5th and 97.5th percentiles were calculated and considered as RI.

RESULTS

In the total population (n=792, age 35-70), RIs for non-HDL-C and remnant-C was 74.0-206.8 and 8.0-52.7 mg/dL, respectively. Age (35-44 and≥45 years) and gender-specific RIs for serum non-HDL-C and remnant-C were determined. Remnant-C and non-HDL-C level were different between sex and age categories. The mean value of all lipid parameters except HDL-C was higher in men, urban residents, subject with age≥45 years and smokers.

CONCLUSION

This is the first study in which the RIs for non-HDL-C and remnant-C in southern Iran are reported. This may help physicians to conveniently use these lipid parameters for patient care and better cardiovascular risk assessment.

The BioRef Infrastructure, a Framework for Real-Time, Federated, Privacy-Preserving, and Personalized Reference Intervals: Design, Development, and Application

BACKGROUND

Reference intervals (RIs) for patient test results are in standard use across many medical disciplines, allowing physicians to identify measurements indicating potentially pathological states with relative ease. The process of inferring cohort-specific RIs is, however, often ignored because of the high costs and cumbersome efforts associated with it. Sophisticated analysis tools are required to automatically infer relevant and locally specific RIs directly from routine laboratory data. These tools would effectively connect clinical laboratory databases to physicians and provide personalized target ranges for the respective cohort population.

OBJECTIVE

This study aims to describe the BioRef infrastructure, a multicentric governance and IT framework for the estimation and assessment of patient group-specific RIs from routine clinical laboratory data using an innovative decentralized data-sharing approach and a sophisticated, clinically oriented graphical user interface for data analysis.

METHODS

A common governance agreement and interoperability standards have been established, allowing the harmonization of multidimensional laboratory measurements from multiple clinical databases into a unified "big data" resource. International coding systems, such as the International Classification of Diseases, Tenth Revision (ICD-10); unique identifiers for medical devices from the Global Unique Device Identification Database; type identifiers from the Global Medical Device Nomenclature; and a universal transfer logic, such as the Resource Description Framework (RDF), are used to align the routine laboratory data of each data provider for use within the BioRef framework. With a decentralized data-sharing approach, the BioRef data can be evaluated by end users from each cohort site following a strict "no copy, no move" principle, that is, only data aggregates for the intercohort analysis of target ranges are exchanged.

RESULTS

The TI4Health distributed and secure analytics system was used to implement the proposed federated and privacy-preserving approach and comply with the limitations applied to sensitive patient data. Under the BioRef interoperability consensus, clinical partners enable the computation of RIs via the TI4Health graphical user interface for query without exposing the underlying raw data. The interface was developed for use by physicians and clinical laboratory specialists and allows intuitive and interactive data stratification by patient factors (age, sex, and personal medical history) as well as laboratory analysis determinants (device, analyzer, and test kit identifier). This consolidated effort enables the creation of extremely detailed and patient group-specific queries, allowing the generation of individualized, covariate-adjusted RIs on the fly.

CONCLUSIONS

With the BioRef-TI4Health infrastructure, a framework for clinical physicians and researchers to define precise RIs immediately in a convenient, privacy-preserving, and reproducible manner has been implemented, promoting a vital part of practicing precision medicine while streamlining compliance and avoiding transfers of raw patient data. This new approach can provide a crucial update on RIs and improve patient care for personalized medicine.

Age and gender-specific reference intervals for a panel of lysophosphatidylcholines estimated by tandem mass spectrometry in dried blood spots

Background and objectives

Very long-chain fatty acyl-lysophosphatidylcholines (VLCFA-LysoPCs) are measured in dried blood spots (DBS) for identifying X-linked adrenoleukodystrophy (X-ALD) and other inherited peroxisomal disorders. Our study aimed to establish age- and gender-specific reference intervals for a panel of LysoPCs measured by tandem mass spectrometry in DBS.

Methods

LysoPCs (26:0-, 24:0-, 22:0- and 20:0-LysoPCs) were estimated by flow injection analysis-tandem mass spectrometry (FIA-MS/MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods in 3.2 mm blood spots of 2689 anonymized, putative normal subjects (1375 males, and 1314 females) aged between 2 days and 65 years. Samples were divided into groups: Neonates (0-1month), Infants (>1m-1year), Children and Adolescents (>1-18years), and Adults (>18years). Reference intervals were determined using the percentile approach and represented as the median with the 1^st and 99^th percentile lower and upper limits.

Results

The percentage coefficient of variation (CV) for repeatability assays of internal and external quality control samples were within acceptable limits. Significant differences (P <0.0001, P <0.01) were observed in the concentrations of 26:0-, 24:0-, 22:0- and 20:0-LysoPCs and their ratios, 26:0/22:0-, 24:0/22:0-, 26:0/20:0-and 24:0/20:0-LysoPC in neonates and infants when compared to children, adolescents, and adults. Levels of 26:0-, 24:0- and 22:0-LysoPCs decreased, whereas 20:0-LysoPC increased with age. There were no significant gender-based differences in the concentration of LysoPCs.

Conclusion

We established age- and gender-specific reference intervals for a panel of LysoPCs in DBS. These reference values would be helpful when interpreting LysoPC values in DBS during screening for X-ALD and other peroxisomal disorders.

Routine clinical chemistry and haematological test reference intervals for healthy adults in the Bhutanese population

Laboratory medicine plays a critical role in the modern healthcare system, and it is reported to influence 60-70% of clinical decision makings. The quantitative laboratory test results are interpreted by comparing to the Reference Intervals (RIs) and therefore the use of appropriate RIs is critical. Clinical laboratories in Bhutan have been randomly using RIs from textbooks and manufacturer's package inserts without even verifying their applicability and therefore lessening their contribution to clinical decision makings. To improve the healthcare service delivery in Bhutan, this study aims to establish routine clinical chemistry and haematological test RIs for healthy adults in the Bhutanese population. Out of 1150 (male, n = 570; female, n = 580) healthy Bhutanese adults listed for the study through a simple random sampling technique, 1002 (male, n = 405; female, n = 597) individuals were assessed and 815 (male, n = 372; female, n = 443) individuals were enrolled in the study. An adequate volume of venous blood was drawn from these participants with the use of standard phlebotomy technique for clinical chemistry and haematological analysis. The laboratory data were analysed with the use of statistical methods recommended by the International Federation of Clinical Chemistry and Laboratory Medicine and Clinical and Laboratory Standards Institute. After excluding the test results indicating underlying pathology and statistically detected outliers, a maximum of 775 (male, n = 346; female, n = 429) and 784 (male, n = 351; female, n = 433) individuals test values were eligible for clinical chemistry and haematology RIs establishment respectively. Statistically, there were no significant differences between age groups of same-sex for both test categories; however, significant differences between sex were observed for various test parameters in both test categories. Our RIs are generally comparable to other published literature. The established RIs are applicable to all the adult Bhutanese population; however, clinical laboratories should validate the transference of these RIs before using them for clinical purposes.

An indirect approach for reference intervals establishment of immunoglobulin A, G and M: the combination of laboratory database and statistics

Immunoglobulins are affected by sex, age and region, so it is necessary to establish suitable reference intervals (RIs) for clinical diagnosis. Various statistical methods were used to calculate RIs, but there has been a lack of comparison among the methods. Research based on immunoglobulin RIs establishment with various methods would provide a methodological basis for further research. A total of 16,525 individuals were enrolled in the study. Individuals were selected in the medical examination center of First Hospital of Jilin University from 2014 to 2020. The lambda-mu-sigma (LMS) method was performed to evaluate the dynamic changes in analytes. RIs were calculated by parametric, non-parametric, Hoffman method and Bhattacharya method. Sex and age partitions were found for immunoglobulins G and immunoglobulin M. The levels of IgM showed no difference with age in males, but showed differences after 50 years of age in females. Circulating immunoglobulin A concentrations showed an increasing trend with age, and immunoglobulin M showed a fluctuating trend with age. Obvious difference (>5%) was commonly found among the four methods, however, the RIs established by the four methods all passed the verification with a high passing rate. Sex and age differences should be considered for immunoglobulins G and immunoglobulin M in clinical practice. The feasibility of the four indirect methods was proven, which would provides a methodological reference for further studies and benefit the application of clinical data.

Derivation of sex and age-specific reference intervals for clinical chemistry analytes in healthy Ghanaian adults

OBJECTVIES

This study is aimed at establishing reference intervals (RIs) of 40 chemistry and immunochemistry analytes for Ghanaian adults based on internationally harmonized protocol by IFCC Committee on Reference Intervals and Decision Limits (C-RIDL).

METHODS

A total of 501 healthy volunteers aged ≥18 years were recruited from the northern and southern regions of Ghana. Blood samples were analyzed with Beckman-Coulter AU480 and Centaur-XP/Siemen auto-analyzers. Sources of variations of reference values (RVs) were evaluated by multiple regression analysis (MRA). The need for partitioning RVs by sex and age was guided by the SD ratio (SDR). The RI for each analyte was derived using parametric method with application of the latent abnormal values exclusion (LAVE) method.

RESULTS

Using SDR≥0.4 as threshold, RVs were partitioned by sex for most enzymes, creatinine, uric acid (UA), bilirubin, immunoglobulin-M. MRA revealed age and body mass index (BMI) as major source of variations of many analytes. LAVE lowered the upper limits of RIs for alanine/aspartate aminotransferase, γ-glutamyl transaminase and lipids. Exclusion of individuals with BMI≥30 further lowered the RIs for lipids and CRP. After standardization based on value-assigned serum panel provided by C-RIDL, Ghanaian RIs were found higher for creatine kinase, amylase, and lower for albumin and urea compared to other collaborating countries.

CONCLUSIONS

The LAVE effect on many clinical chemistry RIs supports the need for the secondary exclusion for reliable derivation of RIs. The differences in Ghanaian RIs compared to other countries underscore the importance of country specific-RIs for improved clinical decision making.

The indirect method in the establishment of reference intervals for complement 3 and complement 4: A retrospective study

Objective

The establishment of reference intervals (RIs) for complement 3 (C3) and complement 4 (C4) is rare, especially by indirect methods. Therefore, this study aims to establish regional RIs for C3 and C4 by an indirect method, using relevant statistical methods.

Methods

Total of 12,313 data points for C3 and 12,125 data points for C4 were obtained from the First Hospital of Jilin University's database in China and standardised using the Tukey and Box-Cox statistical methods. The coefficients of the skewness-median-coefficient of variation curves (LMS) were used to determine the critical value for age, and a subsequent z test used to compare the differences. A non-parametric method was used to establish the RIs.

Results

The C3 and C4 concentrations showed no significant differences by sex, and a weak correlation with age. No significant difference was found after calculating the z value for the age points on the LMS curves. The RIs for C3 and C4 were 0.83-1.58 g/L and 0.15-0.40 g/L, respectively. The RIs all passed verification.

Conclusion

Suitable RIs for C3 and C4 were established for the local population, and will benefit clinical diagnosis. The feasibility and practicability of the indirect method were demonstrated.

Reference intervals for Sysmex XN hematological parameters as assessed in the Dutch Lifelines cohort

OBJECTIVES

Our aim was to derive reference intervals for all Sysmex XN hematology analyzer parameters. The rationale behind the study was the lack of reference intervals for the XN analyzer cell population data (CPD) and functional parameters.

METHODS

Fresh fasting blood samples from 18,484 participants in the Dutch Lifelines study were analyzed using two automated XN analyzers. Structured health questionnaire data were used to select a subgroup of 15,803 apparently healthy individuals for inclusion in the reference population. The Latent Abnormal Values Exclusion (LAVE) approach was used to reduce the influence of latent diseases in the reference population on the resulting reference intervals. We applied analysis of variance to judge the need for partitioning of the reference intervals by sex or age.

RESULTS

We report reference intervals for 105 XN analyzer hematological parameters with and without applying LAVE. Sex-related partitioning was required for red blood cells, (RBC, RBC-O), hemoglobin (HGB, HGB-O), hematocrit (HCT), mean corpuscular hemoglobin concentration (MCHC), reticulocyte production index (RPI), and side scattered light intensity of the red blood cell population in the RET channel (RBC-Z). Partitioning for age was not warranted. Body mass index (BMI) and smoking had moderate influence on a minority of the parameters.

CONCLUSIONS

We provide reference intervals for all Sysmex XN analyzer routine, CPD and functional parameters, using a direct approach in a large cohort in the Netherlands.

Determination of reference intervals from a laboratory database of an academic clinical research unit in a tertiary care teaching hospital and an audit of out of range values

Background

Abnormal laboratory values are a common reason for the exclusion of participants in clinical studies, increasing the recruitment time and cost during conduct. The use of sample-specific reference intervals (RIs) may help to address this issue. Hence, the present study derived site-specific RIs using the department laboratory database and compare the proportion of "out of range" (OOR) values between the new and the old RIs used by the trial site.

Methods

Institutional ethics committee approval was obtained. Data for hematology and biochemistry parameters were analyzed. Normality was assessed and RIs computed using nonparametric method. Data were partitioned for gender and descriptive statistics applied for demographics. The OOR values based on new RIs were compared with old RIs using Chi-squared tests. Between gender OOR proportions compared using Chi-squared test (significance at P< 0.05). Post hoc analysis was performed with Beasley's technique.

Results

Data of 601 participants were analyzed. The median (Inter Quartile Range) age was 22 (47) years and 64.72% were male. New RIs for key parameters were: Haemoglobin (9.3-16.5 g/dl), alanine aminotransferase (11.4-47.74 U/I), aspartate aminotransferase (8.8-58 U/I), total bilirubin (0.27-1.4 mg/dl), and creatinine (0.59-1.36 mg/dl). Post partitioning, the RI for hemoglobin (g/dl) was lower (8.72-15.72) in females. The proportion of OOR values were lower with new RIs relative to old laboratory RIs (P < 0.0001).

Conclusion

A reduction in the proportion of OORs and a change in the upper and lower bound laboratory intervals with new RIs emphasize the need for sample-specific ranges to prevent unnecessary exclusions of volunteers from trials.

Reference intervals for 26 common biochemical analytes in term neonates in Jilin Province, China

Background

Biochemical analytes provide information for neonatal disease management and therapy, and population-based reference intervals (RIs) are essential to accurately interpret laboratory test results. This study aimed to establish local RIs for biochemical assays in term neonates.

Methods

A total of 195 healthy term neonates from birth to 3rd day were recruited as reference individuals prospectively. Analytes of 26 common biochemistries were measured using the VITROS 5600 Integrated System. The 3-level nested ANOVA was performed to assess the need for partitioning RIs of each analyte, and RIs were derived by a nonparametric method or robust method. Multiple regression analysis was used to evaluate specific correlations between the analytes and individual characteristics including age, gender, gestational age, birthweight and delivery mode.

Results

There were no between-sex differences in all analytes, whereas there were significant between-day-age differences in 6 analytes. Small between-delivery-mode differences were observed in the results for potassium, phosphorus, and urea. The major related factor of most analytes was postnatal age. During the first 3 days, values of iron, lipids and lipoproteins increased; creatinine, urea, uric acid, creatine kinase and lactate dehydrogenase decreased; other analytes showed slight changes or relatively stable trends. Reference limits of some analytes, particularly lactate dehydrogenase and alkaline phosphatase, were significantly different from adult and pediatric groups.

Conclusions

RIs of 26 common biochemical analytes are established for term neonates aged 0 to 3 days in northeast China. Additionally, it is suggested that age-related changes should be valued in the clinical decision-making process for newborns.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-021-02565-8.

Establishment of reference intervals of clinical chemistry analytes for the adult population in Egypt

BACKGROUND

This is the first Egyptian nationwide study for derivation of reference intervals (RIs) for 34 major chemistry analytes. It was conducted as a part of the global initiative by the IFCC Committee on Reference Intervals and Decision Limits (C-RIDL) for establishing country-specific RIs based on a harmonized protocol.

METHODS

691 apparently healthy volunteers aged ≥18 years were recruited from multiple regions in Egypt. Serum specimens were analyzed in two centers. The harmonization and standardization of test results were achieved by measuring value-assigned serum panel provided by C-RIDL. The RIs were calculated by parametric method. Sources of variation of reference values (RVs) were evaluated by multiple regression analysis. The need for partitioning by sex, age, and region was judged primarily by standard deviation ratio (SDR).

RESULTS

Gender-specific RIs were required for six analytes including total bilirubin (TBil), aspartate and alanine aminotransferase (AST, ALT). Seven analytes required age-partitioning including glucose and low-density lipoprotein cholesterol (LDL-C). Regional differences were observed between northern and southern Egypt for direct bilirubin, glucose, and high-density-lipoprotein cholesterol (HDL-C) with all their RVs lower in southern Egypt. Compared with other collaborating countries, the features of Egyptian RVs were lower HDL-C and TBil and higher TG and C-reactive protein. In addition, BMI showed weak association with most of nutritional markers. These features were shared with two other Middle Eastern countries: Saudi Arabia and Turkey.

CONCLUSION

The standardized RIs established by this study can be used as common Egyptian RI, except for a few analytes that showed regional differences. Despite high prevalence of obesity among Egyptians, their RVs of nutritional markers are less sensitive to increased BMI, compared to other collaborating countries.

Gender and age-specific reference intervals of common biochemical analytes in Chinese population: Derivation using real laboratory data

BACKGROUND

Indirect sampling methods are not only inexpensive but also efficient for establishing reference intervals (RIs) using clinical data. This study was conducted to select fully normal records to establish ageand gender-specific RIs for common biochemical analytes by laboratory data mining.

METHODS

In total, 280,206 records from 2014 to 2018 were obtained from Peking Union Medical College Hospital. Common biochemical analytes total protein, albumin, total bilirubin (TBil), direct bilirubin (DBil), alanine aminotransferase (ALT), glutamyltranspeptidase (GGT), alkaline phosphatase (ALP), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), potassium, sodium, chlorine, calcium, urea, glucose, uric acid (UA), inorganic phosphorus, creatinine (Cr), total cholesterol, triglyceride, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol] were measured using an automatic analyzer. Sources of variation were identified by multiple regression analysis. The 2.5th and 97.5th percentiles were calculated as the lower and upper limits of the RIs, respectively.

RESULTS

Gender was the major source of variation among the 13 common biochemical analytes with an rp > 0.15. In contrast to the value listed in the WS/T 404, nearly all RIs established in this study were significantly narrower. Furthermore, age-specific RIs should be determined for DBil, LDH, and urea, whereas gender-specific RIs are suggested for GGT, LDH, and urea.

CONCLUSIONS

We recommend that gender-specific RIs should be established for ALT, AST, GGT, DBil, TBil, UA, and Cr as well as genderand age-specific RIs for urea and ALP. Through indirect sampling, ageand gender-specific RIs for common biochemical analytes were established and analyzed.

Determination of reference intervals for common chemistry and immunoassay tests for Kenyan adults based on an internationally harmonized protocol and up-to-date statistical methods

Background

Due to a lack of reliable reference intervals (RIs) for Kenya, we set out to determine RIs for 40 common chemistry and immunoassay tests as part of the IFCC global RI project.

Methods

Apparently healthy adults aged 18–65 years were recruited according to a harmonized protocol and samples analyzed using Beckman-Coulter analyzers. Value assigned serum panels were measured to standardize chemistry results. The need for partitioning reference values by sex and age was based on between-subgroup differences expressed as standard deviation ratio (SDR) or bias in lower or upper limits (LLs and ULs) of the RI. RIs were derived using a parametric method with/without latent abnormal value exclusion (LAVE).

Results

Sex-specific RIs were required for uric acid, creatinine, total bilirubin (TBil), total cholesterol (TC), ALT, AST, CK, GGT, transferrin, transferrin saturation (TfSat) and immunoglobulin-M. Age-specific RIs were required for glucose and triglyceride for both sexes, and for urea, magnesium, TC, HDL-cholesterol ratio, ALP, and ferritin for females. LAVE was effective in optimizing RIs for AST, ALT, GGT iron-markers and CRP by reducing influence of latent anemia and metabolic diseases. Thyroid profile RIs were derived after excluding volunteers with anti-thyroid antibodies. Kenyan RIs were comparable to those of other countries participating in the global study with a few exceptions such as higher ULs for TBil and CRP.

Conclusions

Kenyan RIs for major analytes were established using harmonized protocol from well-defined reference individuals. Standardized RIs for chemistry analytes can be shared across sub-Saharan African laboratories with similar ethnic and life-style profile.

Establishing reference intervals for major biochemical analytes for the Russian population: a research conducted as a part of the IFCC global study on reference values

OBJECTIVES

Because reference intervals (RIs) for biochemistry analytes matched to the Russian population are not well defined, we joined the global study on reference values (RVs) coordinated by the IFCC Committee on Reference Intervals and Decision Limits (C-RIDL).

METHODS

According to the C-RIDL harmonized protocol, 793 healthy volunteers were recruited in Saint-Petersburg, Moscow, and Yekaterinburg. Serum samples were tested for 34 biochemistry analytes. Sources of variation of RVs were explored using multiple regression analysis. The need for partitioning RVs by sex and age were judged using standard deviation ratio based on ANOVA. Latent abnormal values exclusion (LAVE) method was applied to reduce the influence of individuals with metabolic syndrome and/or inappropriate sampling conditions. RIs were computed by the parametric method.

RESULTS

No appreciable between-city differences were observed. Partition of RVs by sex was required for 17 analytes. Age-related changes in RVs were observed in many analytes, especially in females. The trend was exaggerated in nutritional and inflammatory markers that were closely associated with body mass index (BMI), because BMI increases prominently with age. Therefore, for those analytes, volunteers with BMI > 28 kg/m² were excluded in determining RIs for age-specific RIs. The LAVE method was effective in lowering the upper limits of the RIs for nutritional and inflammatory markers.

CONCLUSION

RIs matched to the Russian population were established for 34 biochemical analytes using up-to-date methods in detailed consideration of sources of variation of RVs. The majority of Russian RIs are similar to those of Caucasian populations among the participating countries.

Age- and Sex-Specific Reference Intervals for Myocardial Enzyme Activity in Healthy Chinese Han Population Aged 1∼<18 years

Age- and sex-specific reference intervals (RIs) for myocardial enzyme activity of children and adolescents are not available in China. Our study aimed to establish age- and gender-related RIs for AST, LDH, CK, and CKMB activity in healthy Chinese Han population aged 1∼<18 years. Healthy Han children and adolescents (n = 6322, 1∼<18 years old) were assessed from completed questionnaires and defined criteria from communities and schools in 5 administrative districts of Jilin Province from September 2017 to December 2018. Measurements of AST, LDH, CK, and CKMB activity were performed on the VITROS 5600 Integrated System. Percentiles of enzyme activity were completed by LMS. RIs were established by Medcalc according to the EP28-A3c guidelines issued by the Clinical and Laboratory Standards Institute. AST declined rapidly during 1∼<6 years and had been subsided during 11∼<18 years, though LDH decreased at a steady rate. CK activity stabilized while CKMB showed a downward trend. Sex differences started after age 12 when males presented higher results. There were significant differences comparing with domestic and other countries' experiments which applied similar methodologies. Enzymes were associated with age and sex, while age had greater impact. We established age- and sex-specific RIs of serum AST, LDH, CK, and CKMB activities for Chinese children and adolescents using the VITROS 5600 Integrated System for the first time. These data will lay the groundwork for the next horizon in pediatric RIs as well as improve test result interpretation for pediatric illness.

A new indirect estimation of reference intervals: truncated minimum chi-square (TMC) approach

All known direct and indirect approaches for the estimation of reference intervals (RIs) have difficulties in processing very skewed data with a high percentage of values at or below the detection limit. A new model for the indirect estimation of RIs is proposed, which can be applied even to extremely skewed data distributions with a relatively high percentage of data at or below the detection limit. Furthermore, it fits better to some simulated data files than other indirect methods. The approach starts with a quantile-quantile plot providing preliminary estimates for the parameters (λ, μ, σ) of the assumed power normal distribution. These are iteratively refined by a truncated minimum chi-square (TMC) estimation. The finally estimated parameters are used to calculate the 95% reference interval. Confidence intervals for the interval limits are calculated by the asymptotic formula for quantiles, and tolerance limits are determined via bootstrapping. If age intervals are given, the procedure is applied per age interval and a spline function describes the age dependency of the reference limits by a continuous function. The approach can be performed in the statistical package R and on the Excel platform.