Descriptive analytical data and consequences for calculation of common reference intervals in the Nordic Reference Interval Project 2000

2004 ◽  
Vol 64 (4) ◽  
pp. 343-370 ◽  
Author(s):  
P. Rustad ◽  
P. Felding ◽  
A. Lahti ◽  
P. Hyltoft Petersen
Keyword(s):  
Analytical Data ◽  
Reference Interval ◽  
Reference Intervals ◽  
Common Reference ◽  
Project 2000

Proposal for guidelines to establish common biological reference intervals in large geographical areas for biochemical quantities measured frequently in serum and plasma

2004 ◽  
Vol 42 (7) ◽  
Author(s):  
Pål Rustad ◽  
Peter Felding ◽  
Ari Lahti
Keyword(s):  
Reference Materials ◽  
Standard Procedure ◽  
Reference Interval ◽  
Reference Intervals ◽  
Routine Method ◽  
Common Reference ◽  
Reference Samples ◽  
Project 2000

AbstractA suggestion for a standard procedure to establish biological reference intervals for biochemical quantities by a multicenter approach is presented. This procedure was developed for and used in the Nordic Reference Interval Project 2000 (NORIP). This project established biological reference intervals for 25 frequently requested biochemical quantities through cooperation of 102 Nordic laboratories. Each laboratory performed collection of reference samples and measurement using their routine methods. The bias of each routine method was eliminated by use of common reference materials measured in each of the participating laboratories.

Partitioning biochemical reference data intosubgroups: comparison of existing methods

2004 ◽  
Vol 42 (7) ◽  
Author(s):  
Ari Lahti
Keyword(s):  
Reference Data ◽  
Reference Interval ◽  
Reference Intervals ◽  
New Method ◽  
Poor Correlation ◽  
Specific Reference ◽  
Common Reference ◽  
Reference Limits ◽  
The Common ◽  
The Ideal

AbstractFour existing methods for partitioning biochemical reference data into subgroups are compared. Two of these, the method of Sinton et al. and that of Ichihara and Kawai, are based on a quotient of a difference between the subgroups and the reference interval for the combined distribution. The criterion of Sinton et al. appears rather stringent and could lead to recommendations to apply a common reference interval in many cases where establishment of group-specific reference intervals would be more useful. The method of Ichihara and Kawai is similar to that of Sinton et al., but their criterion, based on a quantity derived from between-group and within-group variances, seems to lead to inconsistent results when applied to some model cases. These two methods have the common weakness of using gross differences between subgroup distributions as an indicator of differences between their reference limits, while distributions with different means can actually have equal reference limits and those with equal means can have different reference limits. The idea of Harris and Boyd to require that the proportions of the subgroup distributions outside the common reference limits be kept reasonably close to the ideal value of 2.5% as a prerequisite for using common reference limits seems to have been a major improvement. The other two methods considered, that of Harris and Boyd and the “new method” follow this idea. The partitioning criteria of Harris and Boyd have previously been shown to provide a poor correlation to those proportions, however, and the weaknesses of their method are summarized in a list of five drawbacks. Different versions of the new method offer improvements to these drawbacks.

scholarly journals Impact of Subgroup Prevalences on Partitioning of Gaussian-distributed Reference Values

2002 ◽  
Vol 48 (11) ◽  
pp. 1987-1999 ◽  
Author(s):  
Ari Lahti ◽  
Per Hyltoft Petersen ◽  
James C Boyd
Keyword(s):  
Reference Interval ◽  
Reference Population ◽  
Reference Intervals ◽  
Source Population ◽  
Distributed Data ◽  
New Model ◽  
Common Reference ◽  
Reference Limits ◽  
Partitioning Problem ◽  
Analytical Expressions

Abstract Background: The aims of this report were to examine how unequal subgroup prevalences in the source population may affect reference interval partitioning decisions and to develop generally applicable guidelines for partitioning gaussian-distributed data. Methods: We recently proposed a new model for partitioning reference intervals when the underlying data distribution is gaussian. This model is based on controlling the proportions of the subgroup distributions that fall outside each of the common reference limits, using the distances between the reference limits of the subgroup distributions as functions to these proportions. We examine the significance of the unequal prevalence effect for the partitioning problem and quantify it for distance partitioning criteria by deriving analytical expressions to express these criteria as a function of the ratio of prevalences. An application example, illustrating various aspects of the importance of the prevalence effect, is also presented. Results: Dramatic shrinkage of the critical distances between reference limits of the subgroups needed for partitioning was observed as the ratio of prevalences, the larger one divided by the smaller one, was increased from unity. Because of this shrinkage, the same critical distances are not valid for all ratios of prevalences, but specific critical distances should be used for each particular value of this ratio. Although proportion criteria used in determining the need for reference interval partitioning are not dependent on the prevalence effect, this effect should be accounted for when these criteria are being applied by adjusting the sample sizes of the subgroups to make them correspond to the ratio of prevalences. Conclusions: The prevalences of subgroups in the reference population should be known and observed in the calculations for every reference interval study, irrespective of whether distance or proportion criteria are being used to determine the need for reference interval partitioning. We present detailed methods to account for the prevalences when applying each of these types of criteria. Analytical expressions for the distance criteria, to be used when high precision is needed, and approximate distances, to be used in practical work, are derived. General guidelines for partitioning gaussian distributed data are presented. Following these guidelines and using the new model, we suggest that partitioning can be performed more reliably than with any of the earlier models because the new model not only offers an improved correspondence between the critical distances and the critical proportions, but also accounts for the prevalence effect.

Albumin and calcium reference interval using healthy individuals and a data-mining approach

2020 ◽  
Vol 57 (5) ◽  
pp. 373-381 ◽  
Author(s):  
N Jassam ◽  
A Luvai ◽  
D Narayanan ◽  
D Turnock ◽  
G Lee ◽  
...  
Keyword(s):  
Metrological Traceability ◽  
Reference Interval ◽  
Reference Population ◽  
Reference Intervals ◽  
Healthy Individuals ◽  
Reference Limit ◽  
Common Reference ◽  
Age Related ◽  
Upper Reference Limit ◽  
Analytical Platforms

Background Harmonization of reference intervals for analytes that have a sound calibration and metrological traceability is a widely recommended practice. The UK Pathology Harmony has recently harmonized reference intervals for calcium and albumin. In this study, we have determined the reference intervals for calcium and albumin on the UK’s most commonly used analytical platforms. Method A prospective reference population of healthy individuals was recruited according to the IFCC CRIDL criteria. A second indirect population was collected from 14 primary care setting and measured in laboratories using various analytical platforms and methods (Roche, Abbott, Beckman and Siemens analytical platforms). Results In total, 299 subjects were recruited; the central 95th centile values for calcium for three out of four analytical platforms were in a close agreement with UK Pathology Harmony reference intervals of 2.2–2.6 mmol/L. Reference intervals of BCG methods from both cohorts and irrespective of analytical platforms were higher for both lower and upper reference limits than those for BCP. In comparison, the indirect study showed an age-related variation. The younger population reference intervals varied by up to 5.7% at the lower reference limit and up to 12% at the upper reference limit compared with Pathology Harmony reference intervals, and the older population showed a variation of up to 14% at both limits. Conclusion While calcium reference intervals can be a subject for harmonization, albumin reference intervals studied showed large variation which is unsupportive of embracing a common reference interval for albumin.

scholarly journals Sources of Variation of Commonly Measured Serum Analytes in 6 Asian Cities and Consideration of Common Reference Intervals

2008 ◽  
Vol 54 (2) ◽  
pp. 356-365 ◽  
Author(s):  
Kiyoshi Ichihara ◽  
Yoshihisa Itoh ◽  
Christopher W K Lam ◽  
Priscilla M K Poon ◽  
Jeong-Ho Kim ◽  
...  
Keyword(s):  
Serum Proteins ◽  
Selection Process ◽  
Reference Interval ◽  
Reference Intervals ◽  
Retinol Binding Protein ◽  
Complement Components ◽  
Common Reference ◽  
Lifestyle Questionnaire ◽  
Sources Of Variation ◽  
Genetic And Environmental Factors

Abstract Background: In a previous study to determine the feasibility of common reference intervals in Asia, we found significant differences among populations from 6 cities. In this study, we attempted to define the sources of these differences. Methods: We enrolled 580 healthy volunteers (279 men, 301 women, 20–62 years old), after a selection process that was based on the Clinical and Laboratory Standards Institute guidelines, and used a lifestyle questionnaire. All sera were obtained at a basal state and frozen at −80 °C until the collective assay was done. We measured 21 basic chemical analytes and 10 serum proteins. Results: We used 3-level nested ANOVA to separate the variation (SD) into between-city (SD-city), between-sex (SD-sex), between-age (SD-age), and between-individual (SD-indiv) components. SD-indiv corresponds to one-quarter of the “pure” reference interval obtained after removing variations due to city, sex, and age. The SD-sex to SD-indiv ratio was >0.8 for creatinine, urate, retinol-binding protein, and transthyretin. We observed high SD-city to SD-indiv ratios, ranging from 0.4 to 0.7, for 11 analytes including lactate dehydrogenase (LDH), electrolytes, IgG, and complement components and SD-age to SD-indiv ratios >0.4 for LDH, alkaline phosphatase, and total cholesterol. Multiple regression analysis demonstrated several other relevant sources of variation, including body mass index, alcohol consumption, and cigarette smoking, although their contributions were generally smaller than those for sex, region, or age. Conclusion: We observed unacceptably large regional differences in measured values of some analytes even after adjustment for age, sex, and lifestyle variables. Genetic and environmental factors may account for the residual differences.

EXPRESS: Method dependent variation in TSH and FT4 reference intervals in pregnancy: a systematic review

2021 ◽  
pp. 000456322110269
Author(s):  
O E Okosieme ◽  
Medha Agrawal ◽  
Danyal Usman ◽  
Carol Evans
Keyword(s):  
Systematic Review ◽  
Reference Interval ◽  
First Trimester ◽  
Reference Intervals ◽  
Assay Method ◽  
Specific Reference ◽  
Upper Limits ◽  
Wide Range ◽  
Assay Methods ◽  
In Pregnancy

Background: Gestational TSH and FT4 reference intervals may differ according to assay method but the extent of variation is unclear and has not been systematically evaluated. We conducted a systematic review of published studies on TSH and FT4 reference intervals in pregnancy. Our aim was to quantify method-related differences in gestation reference intervals, across four commonly used assay methods, Abbott, Beckman, Roche, and Siemens. Methods: We searched the literature for relevant studies, published between January 2000 and December 2020, in healthy pregnant women without thyroid antibodies or disease. For each study, we extracted trimester-specific reference intervals (2.5–97.5 percentiles) for TSH and FT4 as well as the manufacturer provided reference interval for the corresponding non-pregnant population. Results: TSH reference intervals showed a wide range of study-to-study differences with upper limits ranging from 2.33 to 8.30 mU/L. FT4 lower limits ranged from 4.40–13.93 pmol/L, with consistently lower reference intervals observed with the Beckman method. Differences between non-pregnant and first trimester reference intervals were highly variable, and for most studies the TSH upper limit in the first trimester could not be predicted or extrapolated from non-pregnant values. Conclusions: Our study confirms significant intra and inter-method disparities in gestational thyroid hormone reference intervals. The relationship between pregnant and non-pregnant values is inconsistent and does not support the existing practice in some laboratories of extrapolating gestation references from non-pregnant values. Laboratories should invest in deriving method-specific gestation reference intervals for their population.

Evaluation of Thyroid Function in Pregnant Women Using Automated Immunoassays

2021 ◽  
Author(s):  
K Aaron Geno ◽  
Matthew S Reed ◽  
Mark A Cervinski ◽  
Robert D Nerenz
Keyword(s):  
Pregnant Women ◽  
Equilibrium Dialysis ◽  
Reference Interval ◽  
First Trimester ◽  
Reference Intervals ◽  
Free Thyroxine ◽  
Specific Reference ◽  
Childbearing Age ◽  
Thyroid Autoantibody ◽  
The Impact

Abstract Introduction Automated free thyroxine (FT4) immunoassays are widely available, but professional guidelines discourage their use in pregnant women due to theoretical under-recoveries attributed to increased thyroid hormone binding capacity and instead advocate the use of total T4 (TT4) or free thyroxine index (FTI). The impact of this recommendation on the classification of thyroid status in apparently euthyroid pregnant patients was evaluated. Methods After excluding specimens with thyroid autoantibody concentrations above reference limits, thyroid-stimulating hormone (TSH), FT4, TT4, and T-uptake were measured on the Roche Cobas® platform in remnant clinical specimens from at least 147 nonpregnant women of childbearing age and pregnant women at each trimester. Split-sample comparisons of FT4 as measured by the Cobas and equilibrium dialysis were performed. Results FT4 decreased with advancing gestational age by both immunoassay and equilibrium dialysis. TSH declined during the first trimester, remained constant in the second, and increased throughout the third, peaking just before delivery. Interpretation of TT4 concentrations using 1.5-times the nonpregnant reference interval classified 13.6% of first trimester specimens below the lower reference limit despite TSH concentrations within trimester-specific reference intervals. Five FTI results from 480 pregnant individuals (about 1.0%) fell outside the manufacturer’s reference interval. Conclusions Indirect FT4 immunoassay results interpreted in the context of trimester-specific reference intervals provide a practical and viable alternative to TT4 or FTI. Declining FT4 and increasing TSH concentrations near term suggest that declining FT4 is not an analytical artifact but represents a true physiological change in preparation for labor and delivery.

scholarly journals Reference values of plasma homocysteine in Cuban children and adults

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Alina Concepción Alvarez ◽  
Ivette Camayd Viera ◽  
Lisy Vento Buigues ◽  
Yanet Fernández Martínez ◽  
Eraida Hernández ◽  
...  
Keyword(s):  
Reference Values ◽  
High Performance ◽  
Age Groups ◽  
Coffee Consumption ◽  
Reference Interval ◽  
Reference Intervals ◽  
Multifactorial Diseases ◽  
Weak Association ◽  
Different Populations ◽  
Cuban Population

AbstractObjectivesHomocysteine (Hcy) is a nonessential amino acid, produced by the demethylation of methionine. High Hcy levels, or hyperhomocysteinemia, have been associated with genetic and multifactorial diseases. Hcy reference values may vary between different populations, as Hcy levels are affected by factors such as sex, age, diet, smoking, and coffee consumption. The estimation reference interval (RI) allows to establish the normal values of this marker in population. At present, these levels are unknown in Cuba. The aim of this work is to estimate the Hcy reference intervals in Cuban children and adults.MethodsTotal Hcy concentration was quantified by high performance liquid chromatography (HPLC) in plasma. Hcy levels were evaluated in samples from 507 healthy individuals (260 children, 247 adults).ResultsRIs were estimated by nonparametric methods. We found significant differences between both age groups, but we did not find significant differences between sexes, within these groups. The established ranges were 2.56–14.55 µM and 3.63–17.19 µM for children and adults, respectively. Also, we observed a weak association between Hcy levels and age in both sex groups.ConclusionsThis is the first study that assesses Hcy reference values in Cuban population. Our results will allow the introduction of Hcy as a biochemical marker in laboratory testing.

Reference intervals for venous blood gas measurement in adults

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Kirsty L. Ress ◽  
Gus Koerbin ◽  
Ling Li ◽  
Douglas Chesher ◽  
Phillip Bwititi ◽  
...  
Keyword(s):  
Partial Pressure ◽  
Meta Analysis ◽  
Venous Blood ◽  
Reference Interval ◽  
Reference Intervals ◽  
Published Data ◽  
Blood Gas ◽  
Arterial Blood Gas ◽  
Arterial Blood ◽  
Venous Blood Gas

AbstractObjectivesVenous blood gas (VBG) analysis is becoming a popular alternative to arterial blood gas (ABG) analysis due to reduced risk of complications at phlebotomy and ease of draw. In lack of published data, this study aimed to establish reference intervals (RI) for correct interpretation of VBG results.MethodsOne hundred and 51 adult volunteers (101 females, 50 males 18–70 y), were enrolled after completion of a health questionnaire. Venous blood was drawn into safePICO syringes and analysed on ABL827 blood gas analyser (Radiometer Pacific Pty. Ltd.). A non-parametric approach was used to directly establish the VBG RI which was compared to a calculated VBG RI based on a meta-analysis of differences between ABG and VBGResultsAfter exclusions, 134 results were used to derive VBG RI: pH 7.30–7.43, partial pressure of carbon dioxide (pCO2) 38–58 mmHg, partial pressure of oxygen (pO2) 19–65 mmHg, bicarbonate (HCO3−) 22–30 mmol/L, sodium 135–143 mmol/L, potassium 3.6–4.5 mmol/L, chloride 101–110 mmol/L, ionised calcium 1.14–1.29 mmol/L, lactate 0.4–2.2 mmol/L, base excess (BE) −1.9–4.5 mmol/L, saturated oxygen (sO2) 23–93%, carboxyhaemoglobin 0.4–1.4% and methaemoglobin 0.3–0.9%. The meta-analysis revealed differences between ABG and VBG for pH, HCO3−, pCO2 and pO2 of 0.032, −1.0 mmol/L, −4.2 and 39.9 mmHg, respectively. Using this data along with established ABG RI, calculated VBG RI of pH 7.32–7.42, HCO3− 23 – 27 mmol/L, pCO2 36–49 mmHg (Female), pCO2 39–52 mmHg (Male) and pO2 43–68 mmHg were formulated and compared to the VBG RI of this study.ConclusionsAn adult reference interval has been established to assist interpretation of VBG results.

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