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PubMed1992

Reference values for the study of low doses.

At present, the quantitative differences between environmental exposure and occupational exposure to toxic metals are steadily decreasing, it becomes important to establish reference values of the tests used for biological monitoring. However, the word 'reference values' is often used inappropriately and in particular its significance is often confused with that of 'limit values' or 'normal values'. The term reference values defines the levels of the biological indicators in the general population which are not occupationally exposed. It is necessary to refer to these values in order to compare the data obtained through biological monitoring programmes in workers and in groups of the general population which are presumed to be exposed. The most essential aspects for identifying reference values for toxic metals, using a rigorous methodology, are taken into consideration and in particular, the requisites needed for identifying the subjects which must be included in the reference groups are also examined. The modalities for using reference values for individual subjects as well as for groups are then discussed and the main points of research which must be faced in the near future regarding reference values are highlighted.

Environmental Monitoring↗

PubMed1991

[Reference values for spirometry exemplified by FVC and FEV1 parameters--comparison of normal values of the Pathophysiology of Respiration Section and the European Society for Coal and Steel].

Reference values published by the Section Pathophysiology of Breathing in the Society for Pulmology and Tuberculosis of the GDR and reference values of European Community for Coal and Steel (EGKS) were compared on example of FVC and FEV1. It was found a relative well accordance of reference values of FVC and FEV1 in younger and middle-aged men of a height from 160-200 cm (between -5 to +15%). In women with a body height of 150 to 200 cm a well correlation for FVC and FEV1 is also given (-10 to +10%). Reference values are showing a more important difference with increasing age and independent of sex. There are problems concerning the reference values in male and female lower than 155 cm body height.

Adult↗

PubMed1985

Reference values for exercise tests with continuous increase in load.

Reference values for exercise tests with continuous increase in load are presented. The exercise tests were performed on an electrically braked bicycle ergometer by 188 randomly selected Swedes of both sexes who were between 20 and 79 years of age. The reference values are related to sex, age (in decades) and weight and classified in decreasing levels of exercise capacity. Reference values for systolic blood pressure at different work loads are also given.

Adult↗

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↗

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↗

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↗

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↗

PubMed1990

Method for establishing serum ferritin reference values depending on sex and age.

A method is described for the establishment of reference values for serum ferritin depending on sex and age. The results obtained in a stratified random sample of 353 healthy individuals from the Portuguese population revealed that 23% of the variation observed on serum ferritin values was related to sex differences and 6% of the variation was explained by age differences. Furthermore, the effect of age was different in both sexes: serum ferritin values increase with age in females over 40 years and in males under 40. The minimum and maximum reference values were established for the different subgroups of subjects as follows: for females under 40 years and males over 40, reference values were considered as the 2.5 and 97.5 percentiles from the adjusted lognormal distribution; for females over 40 years and males under 40, reference values were considered as the exponential transformation of the upper and lower limits of the 95% prediction intervals for the log of serum ferritin for each particular age point.

Adolescent↗

PubMed1990

Reference values: Bhattacharya or the method proposed by the IFCC?

The Bhattacharya method was used to calculate reference values from unselected patient data. These values were compared with reference values obtained from data from a blood donor population group following the recommendations of the IFCC. Differences between the results could be attributed in part to different statistical methods, and in part to differences between populations. With some limitations, the Bhattacharya method can be of help in the determination of reference values and quality control.

Blood Chemical Analysis↗

PubMed1991

Reference values for some fundamental haemostatic factors in the dog.

The study is a methodological survey to define the reference values for some basic haemostatic parameters in healthy dogs. Reference values for PT, APTT and factors VIII:C and IX:C were studied in 34 dogs. The reference values were (minimum-maximum) 6.5-9.5 and 17.5-26.3 seconds for PT and APTT, 58-260% and 67-163% for VIII:C and IX:C respectively and 185.8-354.4 x 10/1 for platelets. These reference values were applied to 130 other dogs which were presented to the clinic for various treatments or health checks. The results show how haemostatic analysis can be used to resolve delicate interpretation of laboratory results.

Animals↗

PubMedDate not supplied

[Patient data for evaluating reference values].

OBJECTIVE: To explore the use of data in patients as a way to evaluate the values of reference in clinical assays. Serum calcium (Ca) and phosphorus (P) were selected for this purpose. MATERIAL: A total of 836 consecutive admissions in a 10 week period were revised. Seventy percent (580 cases) had data of Ca and P in the first week following admission. A total of 424 were excluded by anyone of the following criteria: a) serum urea greater than 50 mg/dL, b) serum creatinine greater than 1.5 mg/dL; c) serum albumin less than 4 g/dL; d) lack of data of either urea, creatinine or albumin. These cutoff values were selected on the basis of a significant difference (t test) in the mean of Ca and/or P in patients grouped according to levels of the available data. The remainder of 156 cases is the selected population of study, and the 580 with Ca and P is the total population. METHODS: Ca and P were assayed in an analyzer (Coulter Chemistry) using the DAM and the Jaffé methods respectively. The precision during the period of study was adequate (CVs of 2.6% for Ca and 2.9% for P). RESULTS: Table 1 compares the mean, SD and CV of Ca and P in the selected versus the total population. There are significant reductions (F test) in the variability of Ca and P in the selected population (from a CV 9 to 5% in Ca and from 35 to 13% in P). Table 2 compares the age and sex distributions of the selected versus the total population. There are no significant differences (chi square test) although there is a lower proportion of people above 80 years of age in the selected population. The reference intervals of Ca and P in the selected population were obtained with the mean +/- 2 SD as both showed Gaussian distributions. These limits are compared in table 3 versus the values of the institution and of the manufacturer of the analyzer used. The P limits of this study fall intermediate to the other two, but in Ca they are the lowest of the three. Shortly after the completion of this study, the institutional values of Ca were changed to 8.5-10.5 mg/dL on the basis of the one year results in a WHO quality assessment scheme. The modification made the Ca limits of this study also intermediate to the other two series. The small differences in the limits have clinical and economic repercussions. Table 4 shows there is a 20% reduction in the number of abnormal tests (206 vs 259) and in the number of abnormal individuals (165 vs 203) using the limits of this study versus the institutional limits before modification. CONCLUSIONS: The data of Ca and P in a selected but representative population of patients proved to be a reliable way of evaluating its reference intervals. The reference intervals of this study were intermediate to those of the manufacturers of the analyzer and the laboratory (after modification). This finding suggests the strategy may be as good as more conventional approaches to establish reference values.

Adolescent↗

PubMed1991

[Reference values of dipolar electrocardiotopography of the QRS complex].

Reference values of dipolar electrocardiotopogram of ventricular depolarization are presented. The data for establishing reference values in the McFee-Parungao lead system were obtained by manual processing of 145 records of healthy subjects (64 women, 81 men) in the age range of 11-72 years, and for the Frank lead system by automatic processing of 123 records of healthy subjects (54 women, 69 men) aged from 9 to 72 years. The obtained values of the X, Y, Z coordinates of the end points of QRS instantaneous vectors recorded at 10 ms intervals were processed by means of a biomathematical model in the form of activation areas on the spherical image surface. Electrocardiotopograms were represented in the form of discrete spherical image surface in the shape of a rectangle (11 lines, 24 columns). For each point of this matrix the value of relative frequency (probability) of its occurrence in activated state in the healthy population is given.

Adult↗

PubMed1989

Health-based reference values of the Mini-Finland Health Survey: 1. Serum gamma-glutamyltransferase, aspartate aminotransferase and alkaline phosphatase.

The reference values for gamma-glutamyltransferase (GT), aspartate aminotransferase (ASAT) and alkaline phosphatase (AFOS) activities in serum have been produced on the basis of measurements done in the Mini-Finland Health Survey. A representative sample of all Finns aged 30 years or over comprised 8000 persons, of whom 99.2% participated in the actual health survey. Every effort was made to obtain reference values for the healthy ambulatory population. Three separate health-derived selection criteria were used to obtain such reference values for the above-mentioned enzymes: those based on the available literature, with minor modifications, the recommendations published by the Committee on Reference Values of the Scandinavian Society for Clinical Chemistry and Clinical Physiology, criteria that were obtained after subgroup comparisons of the obtained data, where all the factors affecting the enzyme levels were identified. The recommendations of the Expert Panel on Theory of Reference Values (1987) were strictly adhered to in the statistical analyses. The distribution of the serum activity of GT was very skewed. The overall intervals for men and women were 5.1-1460 and 4.7-748 U/l, respectively. The frequency distributions could be transformed to the normal ones logarithmically. The 95% inner reference intervals for GT in the three groups were 7-76, 7-65, and 8-57 U/l for men and 6-35, 6-30 and 6-32 U/l for women, respectively. For ASAT the full intervals of the enzyme levels in serum were 2.6-770 U/l for men and 8.3-172 U/l for women. After logarithmic transformation the respective reference intervals in the three selection groups were 14-42, 14-40 and 13-39 U/l for men and 13-33, 12-31 and 13-33 U/l for women. The full intervals of AFOS were 47.5-2755 and 5.4-816 U/l for men and women, respectively; after the logarithmic transformation the reference intervals of the three selection groups were 98-267, 97-254 and 97-264 U/l for men and 77-265, 75-231 and 75-250 U/l for women, respectively.

Adult↗

PubMed1990

[Principles of determining reference values in hematology].

A short explanation of fundamental terminology concerning reference values is presented. Criteria for formation of a reference group are discussed and the significance of standardization of blood collection and laboratory procedures is emphasized. Interpretation of reference values is founded on the probability theory and attention is directed to non-parametric statistics.

Hematologic Tests↗

PubMed1979

[Reference values of lipid metabolism in childhood (author's transl)].

Sera of 949 children were analyzed for cholesterol and triglycerides by enzymatic methods and for lipoprotein pattern by electrophoresis. For the first time all ages were examined. Two independent collectives were compared: healthy pupils and sick children without disturbances of lipid metabolism. The values of these groups showed no significant difference. In infancy cholesterol and triglycerides levels heavily depend on age, while later in childhood values change little. Highest reference values are 6.36 mmol/l (= 246 mg/dl) for cholesterol and 1.74 mmol/l (= 154 mg/dl) for triglycerides.

Adolescent↗

PubMed1979

[A specific fully enzymatic method for creatinine: reference values in serum (author's transl)].

Reference values for creatinine in serum were established using a fully enzymatic method, adapted to a discontinuous analyzer. Our reference group included 250 females and 215 males (blood donors, hospital staff and patients) aged 18-70 years. Up to 60 years, creatinine concentration did not depend on age, but there was a significant difference between the creatinine concentrations of women and men. We propose reference ranges for creatinine in serum (95% range) of 44-80 mu mol/l for women and of 44-97 mu mol/l for men.

Adolescent↗

PubMedDate not supplied

[Reference values for FVC and FEV1 in healthy adult nonsmokers].

Reference values for FVC and FEV1 have been developed on a sample of 909 healthy adult nonsmokers, men and women, between the ages of 18 to 86 years. The examinees are the inhabitants of Korcula, Brac, Silba, Olib, Pag and the Peljesac peninsula. The lung function parameters were analysed as functions of height and age using full model multiple linear regression analysis. Comparisons with prediction equations for other equally selected populations indicated that even most commonly used equations in Yugoslav medical practice are inadequate for our data. Presently derived reference values are reliable and can be used in daily medical practice.

Adolescent↗

PubMed1986

Pediatric reference values for calcium, magnesium and inorganic phosphorus in serum obtained from Bhattacharya plots for data from unselected patients.

Pediatric reference values for total calcium, magnesium and inorganic phosphorus are given. The values were determined by using Bhattacharya plots for unselected data. The reference values for calcium (from 8320 values from patients) and magnesium (from 1231 values from patients) show only minor dependence on age. Reference values for ages up to 20 years for calcium were 2.14-2.64 mmol/l and for magnesium 0.57-1.12 mmol/l. However, for inorganic phosphorus (3349 values from patients) a gradual decrease in concentration occurred throughout childhood from 1.56-2.29 mmol/l (less than 1 year) to 1.03-1.78 mmol/l (greater than 15 years).

Adolescent↗