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PubMedDate not supplied

Statistical methods of computing reference values for side-to-side differences in nerve conduction studies.

This study uses theoretic derivations, statistical simulations, and empirical estimations to compare two ways of deriving reference values for side-to-side differences in nerve conduction parameters of healthy subjects. The two methods involve using the side-to-side differences (STSD) and the absolute values of the STSD (AVSTSD). The theoretic derivations showed that the population reference value of the AVSTSD is greater than the STSD reference values by 0.18%. Simulation studies showed that the AVSTSD yields greater sampling errors than the STSD method when establishing the reference values for nerve conduction parameters. However, the sampling variability is substantially reduced by using study samples of greater than 50, and the differences between the two methods in sampling errors are trivial as sample size approaches 100. Using H reflex (HR) and extensor digitorum brevis reflex (EDBR) clinical data, the two methods were compared. In contrast to the small theoretic differences in reference values, the AVSTSD method overestimated the reference value by 0.5 ms for the EDBR and 0.1 ms for the H reflex, when using data from a population sample, increasing the type II error (reducing sensitivity) for the EDBR. The STSD method is recommended for establishment of normal values and for clinical comparisons.

Electromyography↗
PubMed1997

Proposal of reference values for home blood pressure measurement: prognostic criteria based on a prospective observation of the general population in Ohasama, Japan.

The purpose of this study was to propose reference values, from a viewpoint of prognostic significance, for blood pressure (BP) measured at home with a semiautomated device (home BP measurement) to differentiate normotension and hypertension. We obtained home BP measurements for 1,913 population-based subjects aged 40 years and over in a rural Japanese community and followed up their survival for a mean duration of 5.0 years. There were 141 deaths during the follow-up period. The association between baseline BP values and the overall mortality was examined by Cox proportional hazards regression model, adjusted for age, gender, and the use of antihypertensive medication. The results indicated that the predictive power of home BP level for subsequent mortality was stronger than that of casual screening BP. There was a linear association between home systolic BP and mortality. The association between home diastolic BP and mortality was nonlinear and well approximated with the secondary degree equation of diastolic BP values. Based on this relation, we propose that the reference value for hypertension is 137/84 mm Hg, and normotension is below 137 mm Hg for home systolic BP and between 66 and 83 mm Hg for home diastolic BP. Home diastolic BP below 66 mm Hg should be considered as low diastolic blood pressure. In this population, home systolic BP of 137 mm Hg and home diastolic BP of 84 mm Hg corresponded to the 80th and 87th percentiles, respectively. Then, 29% of the subjects were classified as having hypertension, 52% as normotension, and 19% as low diastolic blood pressure. All previous studies proposing reference values for home BP measurement, derived from cross-sectional observations, were based on the statistical distribution of home BP values. The reference value must, however, be the one that best predicts the risk for morbidity and mortality from hypertension-related complications. This is the first report proposing reference values for home BP measurement based on prognostic criteria.

Adult↗
PubMed2001

The relationship between the reference value of erythrocyte sedimentation rate and geographical factors.

In order to provide a scientific basis for a unified standard of the reference value of erythrocyte sedimentation rate (ESR) in China, the reference value of healthy people's ESR has been collected. The relationship between the reference value of ESR and geographical factors is examined in this paper. Altitude is the most important factor affecting the reference value of ESR, which decreases with increasing altitude; the relationship is quite significant. The method of stepwise regression analysis was used to deduce two regression equations: Y1 = 12.08 - 0.00222X1 + 0.00114X5 +/- 2.95, Y2 = 18.81 - 0.00323X1 + 0.239X4 +/- 4.70. If the geographical factor value of a particular area in China is known, the reference value of ESR of Chinese people can be calculated by means of the regression equations. Furthermore, the dependence on geographical factors in China can be classified as six districts: Qingzang, Southwest, Northwest, Southeast, North and Northeast.

Adult↗
PubMed1984

Reference values: are they useful?

To answer the question of whether reference values are useful in clinical decision-making, this article addresses the following major controversies: (1) Are reference subjects representative of the group from which they are selected? (2) To what extent should the process of collecting reference values be standardized and controlled? (3) Can a single distribution of reference values be used in an meaningful way in the process of clinical decision-making.

Clinical Laboratory Techniques↗
PubMed1997

Reference values of common blood chemistry analytes in healthy population of Rawalpindi-Islamabad area.

The reference values of common blood chemistry analytes in healthy population, aged newborn to 80 years, of Rawalpindi Islamabad area were determined at AFIP, Rawalpindi. A total of 2115 healthy subjects, 1206 males and 909 females, were included in the study. Plasma glucose was analysed by GOD/POD, serum cholesterol by CHOD/PAP, triglycerides by GPO/PAP, urea by urease/GLDH, creatinine by Jaffe' rate reaction, uric acid by uricase, total bilirubin by Jendrassik and Grof, total protein by biuret, alanine transaminase (ALT) by optimized IFCC and alkaline phosphatase (AP) by optimized DGKC method. The between batch CVs of all the parameters were within acceptable quality goals. The reference values were calculated using 2.5 and 97.5 percentiles as lower and upper limits (95% CI). In healthy adult males the reference values were: fasting plasma glucose, 3.6-6.0 mmol/l; serum cholesterol; 3.2-6.6 mmol/l; triglycerides, 0.6-2.3 mmol/l; urea, 2.8-6.4 mmol/l; creatinine, 65-132 umol/l; uric acid, 164-430 umol/l; total bilirubin, 5-18 umol/l; total protein, 57-83 g/l; ALT, 15-45 U/l and AP, 185-620 U/l. The values in adult females, children and elderly subjects were slightly different than adult males. The reference values of our population show mild to moderate differences from the other Asian, European and American populations. It is recommended that reference values of different biochemical investigations should be established in various areas of Pakistan to make appropriate use of such investigations.

Adolescent↗
PubMed1978

Hematology and clinical chemistry reference values for C57BL/6 X DBA/2 F1 mice.

We have analyzed hematology data from 504 individual male C57BL/6 X DBA/2 (hereafter called B6D2F1) mice. Clinical chemistry data from an additional 304 individual male B6D2F1 mice have also been analyzed. The mice had served as drug-diluent controls in 24 toxicological evaluations of anticancer drugs administered singly or in combination. The studies were carried out under standardized conditions during an 18-month period between July 1975 and December 1976. Test values corresponding to 9 percentiles have been selected from an ordered ranking of values for each of 18 hematologic tests and 18 clinical chemistry tests. Since 95% of the values for a given test are found between the 2.5th and 97.5th percentiles, test values corresponding to these percentiles provide reference values ("normal" values) for these mice. The other percentiles (5th, 10th, 25th, 50th, 75th, 90th, and 95th) indicate the distribution of values between the reference limits for each test. Since values for all tests do not conform to the Gaussian distribution, this nonparametric analysis provides reference values that are more accurate than might be obtained from calculation of the mean and standard deviation of a given test. The B6D2F1 mouse, commonly referred to as BDF1, has been widely used for preclinical evaluation of anticancer drugs, and these data should be useful to investigators who are conducting qualitative and quantitative toxicity evaluations in these mice.

Animals↗
PubMed1995

Subject-based reference values.

Medical decisions based on comparison with group-based reference value have often less than desired sensitivity to significant changes in the biochemical or physiological state of an individual under investigation. Subgrouping of the reference values according to sex, age, or other criteria does frequently not solve this problem. The better solution is to compare new values with old results from the same individual, i.e., with subject-based reference values. Two types of criteria may be used: those based on critical differences between two results (the reference change limit) and those based on time-series models.

Clinical Laboratory Techniques↗
PubMed1978

Measurement of reference values for certain proteins in cerebrospinal fluid.

Reference values are presented for certain cerebrospinal fluid proteins and related indexes, based on determinations carried out on 46 patients with diffuse lower back pain using radial immunodiffusion and electroimmunoassay. A sex difference was noted in total protein and albumin values. The electroimmunoassay method with its sensitivity enhanced by the use of Coomassie Blue staining and optimal antiserum concentrations enabled a reference value to be determined for IgA in cerebrospinal fluid.

Adult↗
PubMed2001

Body mass index reference values (mean and SD) for Swedish children.

UNLABELLED: Body mass index (BMI) is an important indicator of nutritional status. Many studies have been done to present BMI reference values in centile values rather than mean and SD values since its statistical distribution is positively skewed. Both height and weight growth charts are usually available in terms of mean and 1, 2 and 3 SD around the means; it would be of clinical value to produce BMI reference charts in a similar way. The aim of this work was to derive the mean and +/- 1, 2 and 3 SD BMI reference ranges as a supplement to the BMI centile reference values published previously for the same group of Swedish children. The method was based on an age-dependent Box transformation, and the beta-value was given as a third-degree polynomial function over the paediatric age. The BMI reference values can be given from mathematical functions in addition to values for specific ages. CONCLUSION: The BMI reference values and charts derived as described effectively reflect the nature of the variant age-dependent positive skewed statistical distribution of BMI values in the population, and can serve as a valid supplementary tool in the evaluation of growth and nutrition during paediatric years.

Adolescent↗
PubMed1994

Estimation of pooled reference values for cadmium in blood using meta-analysis and TRACY criteria.

Reference values for blood-cadmium levels (B-Cd) are available for only a limited number of geographical areas and for particular population strata (sex, age, smoking habits). This paper, in agreement with the TRACY guidelines, describes and discusses the criteria used to rank published papers on reference values for cadmium retrieved by Medline and Toxline between 1976 and 1991. The TRACY criteria deal with the grading of published papers in terms of their suitability for calculating provisional reference values. Only four out of 18 papers were considered suitable for the TRACY project. The four articles were finally used via meta-analysis to provide provisional reference values for smokers and non-smokers. The comparison of results obtained using published statistics and individual data is used to discuss the appropriateness of meta-analysis in the case of cadmium. Due to the availability of large enough studies and to the clear differences across countries, the suitability of a compound upper reference limit to B-Cd levels seems limited.

Adult↗
PubMed1982

[Joint study to establish reference values for clinical chemical parameters in childhood (author's transl)].

The working group 'Pädiatrische Klinische Chemie' undertook a joint study to satisfy the need for more reliable reference values for clinical chemical parameters in childhood. In 15 different pediatric hospitals data for the most important clinical chemical parameters were determined for children of different age groups. The children included in the study fulfilled the required minimal criteria concerning their health state. The data were listed according to parameter and age group and the percentiles and mean values with 95% confidence intervals are presented. From these values, reference ranges are derived that are suitable for daily routine analyses.

Alanine Transaminase↗
PubMed2003

Reference values for basic human anatomical and physiological characteristics for use in radiation protection.

A new publication prepared by the ICRP Task Group on Reference Man, Basic anatomical and physiological data for use in radiological protection: reference values, is focused on those human characteristics that are important for dosimetric calculations. Moving from the past emphasis on a Reference Man, the new report presents a series of reference values for both male and female subjects of six different ages--newborn, 1, 5, 10, 15 y, and adult. In selecting reference values, the task group has used data on Western Europeans and North Americans because these populations have been well studied with respect to anatomy, body composition and physiology. When appropriate, comparisons are made between the chosen reference values and data from several Asian populations. The reference values for height and body mass are higher than those reported for various Asian populations. However, the reported masses of individual organs and tissues, particularly for China and Japan, are similar to the reference values.

Adolescent↗
PubMed2000

[Hormonal reference values for adrenocortical function in healthy children from Zaragoza].

OBJECTIVE: Estimation of reference values for basal serum concentrations of adrenocorticotropic hormone (ACTH), cortisol, 11-deoxycortisol, 17-OH-progesterone (17-OHP), plasma renin activity (PRA), aldosterone, -4-androstendione ( 4A) and dehydroepiandrosterone sulphate (DHA-S) in healthy children from Zaragoza. METHODS: Reference population were healthy children aged 0 to 14, with normal weight and height, living in the metropolitan area of Zaragoza (Spain). It is a transversal study. Reference values and ranges for ACTH, cortisol, 11-deoxycortisol, 17-OHP, PRA, aldosterone, 4A and DHA-S were estimated, and changes in concentrations were analyzed in relation to age, sex and puberal stage. RESULTS: Reference values have been classified by puberal stage and age in eleven groups for every sex: Tanner I (umbilical cordon, 3 days, 4-30 days, 1-6 months, 6 months-4 years, 4-7 years, 7-10 years, 10-14 years), Tanner II, Tanner III and Tanner IV-V. Sex did not influence ACTH, cortisol, 17-OHP and PRA concentrations, and there are punctual differences in 11-deoxycortisol, aldosterone, 4A and DHA-S levels. 17-OHP, 11-deoxycortisol and aldosterone concentrations significantly decreased from birth to 6 months-4 years and subsequently kept steady. The maximal concentration of ACTH, and ARP in blood cord significantly decreased until the period 6 months-4 years, and subsequent differences among different age groups, and between prepuberal and puberal groups are scarce. The highest concentration of 4A and DHA-S were observed in blood cord and third day of life, decreased until the lowest level in 6 months-4 years and progressively increased with age in prepuberty, and between prepuberty and puberty. The lowest concentration of cortisol was detected in 4-30 days, increased until 6 months-4 years and kept steady along the prepuberty and puberty. CONCLUSION: It is necessary that every population establish own reference values for ACTH, cortisol, 11-deoxycortisol, 17-OHP, PRA, aldosterone, 4A and DHA-S during infancy, childhood and adolescence, according to age, sex and puberal stage.

Adolescent↗
PubMed1989

Steroid profile for urine: reference values.

We describe a project, participated in by 24 institutions in The Netherlands and Belgium, to determine normal reference values for steroids in urine by capillary gas chromatography. Urine samples from 288 healthy volunteers were analyzed in triplicate. Reference values, expressed in mumol/24 h, were determined for androsterone, etiocholanolone, dehydroepiandrosterone, 11-keto-androsterone, 11-keto-etiocholanolone, 11-hydroxyandrosterone, 11-hydroxyetiocholanolone, pregnanediol, pregnanetriol, 11-desoxytetrahydrocortisol, tetrahydrocortisone, tetrahydrocortisol, allo-tetrahydrocortisol, and 17-keto- and 17-hydroxysteroids. We also determined reference ratios for etiocholanolone/androsterone, tetrahydrocortisone/tetrahydrocortisol, and tetrahydrocortisol/allo-tetrahydrocortisol; an upper limit of a discriminant function to establish polycystic ovarian disease; and reference values for 24-h urine volume and creatinine excretion. Reference values were determined separately for men and women, each in six age categories: 0-3 months, 4 months-12 years, 13-16 years, 17-50 years, 51-70 years, and older than 70 years. We conclude that these reference values are reliable and form a basis for quantitative interpretation of steroid profiles.

Adolescent↗
PubMed1996

Selenium and glutathione peroxidase reference values in whole blood and plasma of a reference population living in Valencia, Spain.

In order to assess the reference values for selenium nutritional status, adequate indicators (selenium concentration and glutathione peroxidase activity) were determined in whole blood and blood derivates of a healthy population (n = 287) from the province of Valencia, Spain. The reference population was selected by applying preestablished criteria. Selenium in whole blood and plasma was measured by graphite furnace atomic absorption spectrometry (GFAAS), with a deuterium correction, after addition of Pd/Mg(NO3)2 as the matrix modifier and appropriate dilution. Accuracy was checked by means of a reference material (Seronorm Trace Metals serum and whole blood). The population's reference intervals for selenium content at a 95% confidence level were: 53.03-108.96 and 66.71-119.4 mg/L for plasma and whole blood selenium concentration respectively. GPX activity was measured using a modification of the Paglia and Valentine method, and the reference intervals obtained ranged from 196 to 477 U/L in plasma, from 49 to 93 U/gHb in erythrocytes and from 52 to 96 U/gHb in whole blood. The only statistically significant differences detected between men and women are for to the GPX activity in whole blood. The results obtained are in the range of values found by others authors in healthy populations residing in different European countries.

Adolescent↗
PubMed2004

Inherent biological variation and reference values.

There is a need for revisiting theoretical concepts and practical applications of conventional population-based reference values to make for better clinical use of laboratory data. Knowledge of the underlying biological variation of quantities examined in medical laboratories is vital to understanding the proper generation and application of traditional population-based reference values. Appreciation of the biological changes that occur over the span of life is a necessary prerequisite to deciding whether stratification of reference values according to age is likely to be necessary. Knowledge of the detail of predictable biological cyclical rhythms is required for correct clinical interpretation of laboratory data and appropriate collection of specimens at times relevant to the clinical purpose. Quantitative data on inherent within- and between-subject biological components of variation have shown the marked individuality of most quantities of interest in laboratory medicine. This individuality casts light on why examinations are not generally very successfully applied in population screening or case-finding. Consideration of individuality demonstrates why stratification of reference values is often very advantageous. Individuality provides an indisputable argument for better use of individual specific reference values.

Humans↗
PubMed2005

Reference values for exposure to PAH contaminants: Comparison of fish from Ohio and Mid-Atlantic streams.

Reference values for background exposures of benzo[a]pyrene (BAP)- and naphthalene (NAPH)-type metabolites were calculated for white sucker, northern hog sucker, and rock bass from the mid-Atlantic region based on the 90th percentile of a probability-based sample. Preliminary findings are presented for common carp. Bile was collected from fish and assayed for polycyclic aromatic hydrocarbon metabolites using the fluorescent method of Lin et al. Exposure reference values for white sucker were 0.3 microg/mg protein for BAP-type metabolites and 40 microg/mg protein for NAPH-type metabolites. Values from the Mid-Atlantic region were similar to those previously reported for the Eastern Corn Belt Plains (ECBP) ecoregion. Exposure reference values of BAP-type metabolites for rock bass were 0.3 microg/mg protein and 0.4 microg/mg protein for northern hog sucker. Exposure reference values of NAPH-type metabolites for rock bass were 30 microg/mg protein for rock bass and 50 microg/mg protein for northern hog sucker. Provisional values for common carp based on 39 observations are 0.4 microg/mg protein for BAP-type metabolites and 120 microg/mg protein for NAPH-type metabolites. Small streams exhibited the greatest range of exposures, 0.015-0.689 microg/mg protein for BAP-type metabolites and from 5.7 to 159 microg/mg protein for NAPH-type metabolites. Larger streams had 0.11-0.859 microg/mg protein for BAP-type metabolites and 10.2-286.5 microg/mg protein for NAPH-type metabolites. Exposure reference values for BAP and NAPH-type metabolites could be used as a basis of comparison of exposure to PAH contamination.

Animals↗
PubMed1982

Lung-function reference values from Victorian power-industry workmen.

Reference values for a number of lung function tests performed on a group of apparently healthy Victorian power industry workmen are described. Most workers in this industry have had at least incidental exposure to a range of respiratory hazards, including asbestos dust, at some time in their working lives, but men who recalled handling asbestos materials were excluded from the study. Comparison with other published Australian data shows considerable variation. Differences such as measurement technique, equipment calibration, occupational factors, and selection bias must be considered when reference values from published reports are used for clinical or epidemiological purposes.

Adult↗