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PubMedDate not supplied

[Reference values of T-lymphocyte subsets in umbilical cord blood].

In order to determine reference values of T lymphocyte subpopulations in cord blood in the metropolitan area of Puebla city we randomly selected 80 from a total of 400 term, eutrofic and without pathology newborn. The percentage of CD3, CD4 and CD8 T lymphocyte subpopulations in cord blood were determined by flow cytometry. Reference values were gotten from the 25 and 75 percentile in parameters without gaussian distribution. Reference values are CD3 (45.5 to 91.3%), CD4 (26.2 to 69.4%), CD8 (16.2 to 24.1%) and NK (2.0 to 8.5%). The presented data represent valuable normal ranges of T lymphocyte subsets to compare with values observed in sick or in risk of developing immunoallergic pathology children.

Cross-Sectional Studies↗

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↗

PubMed1993

A guide to IFCC recommendations on reference values.

Six recommendations on the theory, production, and use of reference values have been prepared by the IFCC's Expert Panel on Theory of Reference Values. This review serves as a guide to the documents and presents the main topics.

Chemistry, Clinical↗

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↗

PubMed1995

Spirometric reference values in school children from Dalmatia.

Data on spirometric reference values in children are based on small, selected populations. We performed spirometric testing (forced vital capacity (FVC); forced expiratory volume in one second (FEV1); forced mid-expiratory flow rate (FEF25-75%)) in 2,500 healthy nonsmoking school children (1,250 boys and 1,250 girls) in the region of Dalmatia, Croatia. Significantly higher FVC and FEV1 values were noted in boys. Standing and sitting heights correlated significantly with FVC and FEV1 in boys and girls. Regression equations were derived, utilizing the multiple linear regression analysis, for FVC, FEV1 and FEF25-75% related to five (sex, age, weight, standing and sitting heights) or three (sex, age and standing height) variables. The reference spirometric values in the Dalmatian school boys were in close agreement with Knudson et al., while the values in girls were closest to those of Knudson et al. and Cotes et al. It is suggested that for calculation of ventilatory reference values in boys and girls the age and the standing height should be used.

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↗

PubMed2003

Serum insulin-like growth factor I reference values for an automated chemiluminescence immunoassay system: results from a multicenter study.

BACKGROUND: Analysis of insulin-like growth factor I in serum (S-IGF-I) is an integral component in the diagnosis of GH-related disorders and is going to be of interest in the diagnosis and follow-up of many disorders. The objective of the present study was to develop cross-sectional reference values for S-IGF-I measured by an automated chemiluminescence immunoassay (Nichols Advantage). METHODS: The study included samples from 3,961 healthy subjects (2,201 males, 1,760 females) aged 1 month to 88 years. Six laboratories were involved in this study and the samples were analyzed by one of seven automated immunoassay systems run in these laboratories. For data analysis, polynomial age and sex-specific models were fitted after transformation of S-IGF-I values. RESULTS: The results show the well-known age dependency of S-IGF-I levels. At ages <20, higher S-IGF-I levels were seen in girls with an estimated mean peak of 410 microg/l at age 14 and an estimated mean peak of 382 microg/l at age 16 in boys. Thereafter, a rapid decrease was seen to approximately 25 years of age, followed by a slow age-dependent decrease. In adulthood, S-IGF-I in males were slightly, but significantly higher than in females. It could be shown that the mean values of some reference sample subgroups differed significantly from the total mean. However, the multicenter approach used in this study reduces the impact of systematic population, sample handling and laboratory differences on the calculated reference mean. CONCLUSION: The present study establishes age- and sex-specific reference values for a fully automated immunoassay system based on a large population of healthy subjects. The established reference values may be used for this immunoassay system in different laboratories provided that the systematic difference between systems is low.

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↗

PubMed1989

[Aging and reference values of the parameters in optokinetic nystagmus].

Changes in optokinetic nystagmus by age were assessed, and preparation of reference values by age was made by the use of the data from 834 reference subjects. As a result, changes by age were observed at the test on optokinetic nystagmus. The reference values by these changes can be approximated with the quadratic and was considered, therefore, to be useful clinically. Four parameters were set for the test items for optokinetic nystagmus as the total number of nystagmus (NYS); the mean of eye velocity during the fast phase of nystagmus (FM); the algebraic summations of eye velocity (VEL) and amplitude (AMP) during the slow phase of nystagmus. As the process for statistical analysis, variables were divided into 7 groups, and after removing outlier (any extraneous data) in each group, changes in variables by age were assessed by the one-way analysis of variance and the method of multiple comparison (Ryan's method). As a result: 1) the age group of each variable seemed to develop into normal distribution; 2) it was presumed that change in NYS by age is less; 3-1) regarding FM, VEL and AMP, no change was observed in the variable by ages on 30s and 40s; and 3-2) however, decrease in the measured value was observed in ages on 60s along with aging. From these, the ages on 50s are the generation when the measured values of optokinetic nystagmus change. On the other hand, the reference values calculated, taking age into consideration, could be approximated with the quadratic.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1994

Reference values for luteal progesterone measured by salivary radioimmunoassay.

OBJECTIVE: To establish age-stratified reference values for salivary luteal P levels. DESIGN: One hundred thirty-six regularly menstruating women (18 to 48 years of age), screened for weight, exercise, and steroid medication use, collected daily saliva samples for one complete menstrual cycle. Luteal P levels were measured by 3H-RIA, and data were aligned by day of next menstrual onset. Means (+/- 1 SD range) and percentiles, calculated using both untransformed and log transformed data, were calculated for each luteal day and for indices of luteal P production. RESULTS: Reference values for salivary daily luteal P levels and indices of luteal P are presented for three age groups (18 to 24 years, 25 to 39 years, and 40 to 48 years). CONCLUSION: The age-stratified reference values presented here can be used, without collateral clinical procedures, to assess salivary luteal P levels. Salivary monitoring is ideally suited for research and long-term clinical observation, but the characteristics of salivary P data may limit the usefulness of these values for individual diagnosis.

Adolescent↗

PubMed1999

Differences in spirometry reference values: a statistical comparison of a Mongolian and a Caucasian study.

New reference value studies for spirometry are commonly compared to existing reference value studies using average data derived from existing reference equations. Such comparisons are inherently flawed because they do not account for differences in distributions of the independent and dependent variables and they do not have identical methodologies. This study was undertaken 1) to derive reference equations for forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) for natives of Mongolia and 2) to compare the Mongolian data with data from a 1981 reference study of Caucasians in Salt Lake City, UT, USA. Spirometry was performed on 344 (176 male, 168 female) healthy, nonsmoking urban natives of Mongolia to generate reference equations for FVC, FEV1, and FEV1/FVC. These data were compared with data from a 1981 reference study of Caucasians in Salt Lake City, using both an analysis of covariance of the raw data and parametric and nonparametric comparisons of a matched pair subset. Average measured forced vital capacity and forced expiratory volume in one second in native Mongolians were within 1-2% of the Caucasian predicted values. These small differences are not statistically significant in any of the multiple methods of comparisons. Power analysis suggests that, if real differences exist, the differences in forced vital capacity are <155 mL for males, <105 mL for females, and the differences in forced expiratory volume in one second are <107 mL for males and <76 mL for females.

Adolescent↗

PubMed1995

[Pilot project for evaluation of lung function reference values].

Lung function tests were performed in this study on 139 adults (mean age 36 years), as well as on 91 female persons between 16 and 18 years of age (the latter just starting on their professional careers), the lungs being healthy in each case in both groups. The findings were compared with the currently accepted reference value formulae after Quanjer et al., and Zapletal as well as further developed reference value formulae after Brändli et al., Most of the measurement data obtained by spirometry for the BGFA group of probands are between the two recommended reference values for adults with better coincidence with Brändli's predictions (exceptions being MMEF25-75 MEF 50 and MEF 25). In our studies we obtained higher values than the reference median values after Quanjer and Zapletal for IVC, FVC, FEV1 and PEF by 6-8% and 5-15%, respectively, whereas the values for adults differ from the predictions made by Brändli et al. by -4% to +5%. The flow data MMEF 75-25, MEF 50 and especially MEF 25 are set at too low levels (by 5-23%) by Zapletal's and Brändli's values. Comparatively, the values predicted by Quanjer et al. for the above mentioned flow-volume parameters (with the exception of MEF 75) are too high by 4% to 12%. There are also considerable differences in respect of the reference values for IGV to the tune of +15% in the BGFA group compared to Quanjer et al.; in the BAFAM group the values differ from those of Zapletal et al. by +17%. RV yields results in the BGFA group which are higher by 11% than according to Quanjer's formulae, whereas in the BAFAM group they are higher by 15% compared to Zapletal's predictions. In respect of Rt there are differences to the predictions by Rühle and Matthys by +16% (BGFA group) and +13% (BAFAM group), respectively. The BAFAM group differs from Zapletal's predictions by +11%. Looking at the reference limit values the overall impression is confirmed that the predictions after Quanjer et al. and mostly also those by Zapletal are too low in respect of the abovementioned lung function parameters (in the majority of cases not 5% of the examined probands, as expected, are below those levels, but only about 2%). Females, who had been underrepresented in the previous healthy proband groups, show larger deviations than males in respect of most of the parameters.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗

PubMed1980

The use of patient data for the calculation of reference values for some haematological parameters.

We have investigated the use of patient data for the calculation of reference values for the parameters which are determined by the Hemalog. For this purpose we used the Bhattacharya plot. All the parameters, with the exception of leukocytes, appear to meet the main underlying assumption of this plot, namely that the frequency distribution is Gaussian. In the case of leukocytes, however, the frequency distribution could be resolved into two overlapping Gaussian curves, thus making it possible to calculate reference values for this parameter also. The reference values as calculated from 14,500 unselected data (excluding children) are in general agreement with the literature. Significant differences were however detected between a group of patients and a group of blood donors. When a Bhattacharya plot has to be constructed with relatively few data, smoothing of the observed frequencies is very helpful in deciding which part of the plot is linear. Smoothing was carried out using the least squares method with a quadratic equation. Since the classes are equally spaced, this involves only a simple numerical transformation of the frequencies.

Blood Donors↗

PubMed2006

Reference values for metabolites of pyrethroid and organophosphorous insecticides in urine for human biomonitoring in environmental medicine.

Pesticides are widely used throughout the world in agriculture to protect crops, and in public health to control diseases transmitted by vectors or intermediate hosts. After the prohibition of organochlorines, such as DDT, today mainly pyrethroids and organophosphorous insecticides are used. With reliable and sensitive analytical methods for detecting metabolites of organophosphorous and pyrethroid insecticides in urinary specimens of the general population several studies have been published on internal exposure to these insecticides of the population in Germany. In total, data on levels of metabolites of organophosphorous acids in urine of about 1200 children and adults have been published, as well as data on levels of pyrethroid metabolites in urine of about 2100 children and adults. In Germany, reference values for environmental pollutants related to the population are established continuously by the Human Biomonitoring Commission of the German Federal Environmental Agency, preferably based on data gained by representative studies. Reference values are defined as the 95th percentile, rounded off within the 95% confidence interval of the population studied. Since there is a need for reference values to characterise the population's exposure to organophosphates and pyrethroids, and since there are different studies available from Germany that agree quite well with data from other industrialised countries, the Commission has derived reference values from the available data, though none of the studies had fulfilled criteria on representativity. Reference values for metabolites of organophosphorous acids are as follows: DMP 135 microg/l, DMTP 160 microg/l and DEP 16 microg/l and for metabolites of pyrethroids: cis-Cl2CA 1 microg/l, trans-Cl2CA 2 microg/l and 3-PBA 2 microg/l. As the volume-related concentrations of organophosphate and pyrethroid metabolites show no significant age-dependence, the reference values derived are not age-stratified. Though based merely on statistical and not on toxicological data, levels analysed above the reference levels, when reliably measured (verified several times), should prompt environmental health practitioners to search for sources, within the bounds of proportionality. In addition to accidental poisoning, possible sources include indoor contamination following improper pest control operations in homes as well as in pets and food products contaminated by these pesticides.

Adolescent↗

PubMedDate not supplied

Calculation of reference values for lung function tests.

The powerful computers that are now available enable calculation of reference values by endless permutations of regression models that are not always biologically meaningful. The aim of this study was to test the ability of simple regression models to describe data that has been collected for calculation of reference values. Healthy non-smoking females (n = 74) and males (n = 51) were studied with 22 commonly used lung function tests. If the data were logarithmically transformed, there was a satisfactory reduction of residual variation and the assumption of normality was fulfilled. Furthermore, the difference between males and females could be described by a binary sex-variable that is independent of interactions with other variables such as age, height and weight. Logarithmic transformation of lung function measurements followed by linear regression is recommended as a simple standard method for calculation of reference values.

Adult↗

PubMed2006

[Spirometric reference values in 5 large Latin American cities for subjects aged 40 years or over].

OBJECTIVE: In clinical practice, spirometry is a extremely useful test that requires strict quality control, an appropriate strategy for interpretation, and reliable reference values. The aim of this study was to report spirometric reference values for 5 cities in Latin America. PATIENTS AND METHODS: From data for 5315 subjects who had undergone spirometry in the PLATINO study in Caracas, Mexico City, Santiago, São Paulo, and Montevideo, we selected information for 906 (17%) individuals aged between 40 years and 90 years to provide reference values. The chosen subjects had never smoked, were asymptomatic, had not been diagnosed with lung disease, and were not obese. Multiple regression models were constructed with the following spirometric parameters: forced expiratory volume in 1 second (FEV1) and in 6 seconds (FEV6), peak expiratory flow, forced vital capacity (FVC), FEV1/FEV6, FEV1/FVC, and forced midexpiratory flow rate. Height, sex, and age were also included in the model. RESULTS: Average values for the subjects studied were similar to those for the white North American population and the Mexican-American population of the third National Health and Nutrition Examination Survey, but exceeded those of the black population of the same survey by 20%. CONCLUSIONS: The proposed reference values are an improvement on those currently available for Latin America because the participants were chosen by population sampling methods and standardized up-to-date methodology was used.

Adult↗

PubMed1998

Significance and utility of reference values in occupational medicine.

Although it is generally accepted that reference values can be included among the instruments of modern occupational medicine, problems arise when applying them from clinical chemistry to the needs of occupational medicine. Here some general aspects regarding reference values beginning from their theoretical basis, their significance and importance and their possible use in occupational medicine are reviewed. Furthermore, their relationship with other more familiar 'guideline values', such as action levels and limit values, is demonstrated.

Guidelines as Topic↗

PubMed2004

Guideline for the production of multicentre physiological reference values using the same measurement system. A proposal of the Catalan Association for Clinical Laboratory Sciences.

This article is intended as a guide for the production of biological reference values of healthy people (physiological reference values) by several clinical laboratories using the same measurement system. This guide is a proposal from the Catalan Association of Clinical Laboratory Sciences to be applied worldwide at a regional level. This guide makes it possible for all clinical laboratories in a region using the same measurement system to adopt the same physiological reference limits. The model presented here is based on the assumption that the production of physiological reference values is a professional task that should be shared by both clinical laboratories and the in vitro diagnostics industry.

Clinical Chemistry Tests↗