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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↗
PubMed1993

Reference values for organ weight, hematology and serum chemistry in the female ferret (Mustela putrius furo).

Organ Weight, hematologic and blood chemistry values were determined to establish reference values in the female ferret. Organ weight per kg body weight was calculated for various organs. Body surface area (BSA) was also determined by the direct method, and K values (constant) were calculated. The K value was 3.48 in the Dubois and Dubois equation, and 9.69 in the Meeh-Rubner equation. Blood samples were used to record 10 hematologic and 57 serum (plasma) chemistry values, and 7 immunological parameters. Among hematologic values, values whose coefficient of variation (cv) exceeded 30% were RBC, WBC and PLT. In blood chemistry, the CV of gamma-G, UA, ZTT, GPT, gamma-GTP, MAO, ALD and IgG exceeded 30%. In the total amino acid analysis, only the CV of TAU exceeded 30%. Electrophoretograms of amylase and CPK isozyme were quite different from those of humans. Although 1-MEHIS, 3-MEHIS and CAR have not been detected or are present in trace amounts in human plasma, concrete values were detected in female ferret plasma. Hematologic and serum chemistry values were in general agreement with normal values seen in cats and dogs. However, the alpha 1-G percentage, and ALP and amylase activities were lower than the corresponding values in cats and dogs. The RBC count, RET-C percentage and LDH activities were higher than in cats and dogs. Since there have been no comprehensive articles on reference values for the female ferret, the present report contributes to studies that involve this animal as an experimental model.

Alanine Transaminase↗
PubMed2006

Wide variability in laboratory reference values for serum testosterone.

INTRODUCTION: The laboratory determination of testosterone levels consistent with a diagnosis of hypogonadism is complicated by the availability of multiple testosterone assays and varying reference ranges. AIM: To assess current laboratory practices regarding availability of testosterone assays and use of reference values. METHODS: A telephone survey of 12 academic, 12 community medical laboratories, and one national laboratory. MAIN OUTCOME MEASURES: Types of androgen assays offered and determination of reference values. RESULTS: All of the academic and eight of the community centers performed total testosterone testing. Free testosterone was performed in-house by six of the 12 academic and one community center. Testing for bioavailable testosterone, free androgen index, and percent free testosterone was performed in-house by no more than two centers. There were eight and four different assays used for total and free testosterone, respectively. One national laboratory offered equilibrium dialysis measurement of free testosterone. Of the 25 labs, there were 17 and 13 different sets of reference values for total and free testosterone, respectively. The low reference value for total testosterone ranged from 130 to 450 ng/dL (350% difference), and the upper value ranged from 486 to 1,593 ng/dL (325% difference). Age-adjusted reference values were applied in four centers for total testosterone and in seven labs for free testosterone. All reference values were based on a standard statistical model without regard for clinical aspects of hypogonadism. Twenty-three of the 25 lab directors responded that clinically relevant testosterone reference ranges would be preferable to current standards. CONCLUSIONS: Laboratory reference values for testosterone vary widely, and are established without clinical considerations.

Androgens↗
PubMedDate not supplied

Technical note: reference values of haematocrit in young people and relationship with altitude.

The purpose of this paper is to provide scientific basis for a unified standard reference value of haematocrit in young people in China. The reference values of haematocrit levels in healthy young people have been collected according to the Wintrobe methods; the relationship between the reference values of haematocrit in young people and altitude has been tested in this paper. It has been found that the reference value of haematocrit in young people increases when the altitude gradually increases, and such relationship is quite significant, The method of mathematical univariate regression analysis is used to deduce two regression equations: Y1 = 44.3 + 0.00357X +/- 3.7, and Y2 = 39.7+0.00318X +/- 2.6. If the altitude value of a s known, the particular area of China is known, the reference value of haematocrit in young people there can be calculated by means of the regression equations. Furhermore depending on the altitude, China can be divided into three districts: Qingzang District, Central District and Eastern District.

Adolescent↗
PubMed2004

Normal reference value of hemoglobin of middleaged women and altitude.

AIM: In order to supply a scientific basis for uniting the normal reference value standard of hemoglobin of Chinese middlescent women. METHODS: A research is made about the relationship between the normal reference value of 25,917 examples of hemoglobin of middlescent women and altitude in 268 areas in China, the normal reference values of hemoglobin of middlescent women are determined by the hemoglobincyanide method. RESULTS: The correlation between the normal reference value of hemoglobin of middlescent women and altitude is quite significant (r = 0.827). By using the method of univariate linear regression analysis, one regression equation is inferred. CONCLUSION: If the altitude values are obtained in some areas, the normal reference value of hemoglobin of middlescent women of this area can be reckoned by using the regression equation. Furthermore, depending on the altitude, China can be divided into three districts: Qingzang District, Central District, and Eastern District.

Altitude↗
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↗
PubMed1999

Spirometric reference values from a sample of the general U.S. population.

Spirometric reference values for Caucasians, African-Americans, and Mexican-Americans 8 to 80 yr of age were developed from 7,429 asymptomatic, lifelong nonsmoking participants in the third National Health and Nutrition Examination Survey (NHANES III). Spirometry examinations followed the 1987 American Thoracic Society recommendations, and the quality of the data was continuously monitored and maintained. Caucasian subjects had higher mean FVC and FEV1 values than did Mexican-American and African-American subjects across the entire age range. However, Caucasian and Mexican-American subjects had similar FVC and FEV1 values with respect to height, and African-American subjects had lower values. These differences may be partially due to differences in body build: observed Mexican-Americans were shorter than Caucasian subjects of the same age, and African-Americans on average have a smaller trunk:leg ratio than do Caucasians. Reference values and lower limits of normal were derived using a piecewise polynomial model with age and height as predictors. These reference values encompass a wide age range for three race/ethnic groups and should prove useful for diagnostic and research purposes.

Adolescent↗
PubMed1993

Deriving reference values in electrodiagnostic medicine.

Traditional methods for determining nerve conduction reference values have usually involved studying a group of normal controls, and determining the mean +/- 2 standard deviations (SD) for each parameter. Recent studies suggest other factors should be taken into account. Height has a greater effect on conduction velocity than age or temperature. The common assumption that conduction values follow a normal, bell-shaped Gaussian distribution appears unwarranted. The curve for some conduction parameters is significantly skewed, making a mean +/- 2 SD definition of normality inaccurate to a clinically important degree. In developing and using reference values one should consider height, age, and temperature, and calculate the mean +/- 2 SD of the transformed data to remove the effects of skew. Reference values provide only a guide to the probability a given result came from a healthy or diseased individual; one should therefore seek multiple internally consistent abnormalities before diagnosing disease on the basis of electroneurography.

Body Height↗
PubMed2001

The relationship between reference value of old people's erythrocyte sedimentation rate and altitude.

In order to provide a scientific basic for a unified standard of the reference value of old people's erythrocyte sedimentation rate (ESR) in China. The reference value of healthy old people's ESR was collected according to the Wintrobe method, the relationship between the reference value of old people's ESR and altitude was tested in this paper. It was found that the reference value of old people's ESR decreases when the altitude gradually increases, the relationship is quite significant. The method of mathematical univariate regression analysis was used to deduce two regression equations: Y1 = 16.38 - 0.00301X +/- 6.53, Y2 = 25.92 - 0.00438X +/- 10.25. If the altitude value of a particular area of China is known, the reference value of old people's ESR can be calculated by means of the regression equations. Furthermore, depending on the altitude, China can be divided into three districts: Qingzang Districts, Central Districts and Eastern Districts.

Aged↗
PubMed2001

Determination of reference values for glucose tolerance, insulin tolerance, and insulin sensitivity tests in clinically normal cats.

OBJECTIVE: To determine reference values and test variability for glucose tolerance tests (GTT), insulin tolerance tests (ITT), and insulin sensitivity tests (IST) in cats. ANIMALS: 32 clinically normal cats. PROCEDURE: GTT, ITT, and IST were performed on consecutive days. Tolerance intervals (ie, reference values) were calculated as means +/- 2.397 SD for plasma glucose and insulin concentrations, half-life of glucose (T1/2 glucose), rate constants for glucose disappearance (Kglucose and Kitt), and insulin sensitivity index (Si). Tests were repeated after 6 weeks in 8 cats to determine test variability. RESULTS: Reference values for T1/2glucose, Kglucose, and fasting plasma glucose and insulin concentrations during GTT were 45 to 74 minutes, 0.93 to 1.54 %/min, 37 to 104 mg/dl, and 2.8 to 20.6 microU/ml, respectively. Mean values did not differ between the 2 tests. Coefficients of variation for T1/2glucose, Kglucose, and fasting plasma glucose and insulin concentrations were 20, 20, 11, and 23%, respectively. Reference values for Kitt were 1.14 to 7.3%/min, and for SI were 0.57 to 10.99 x 10(4) min/microU/ml. Mean values did not differ between the 2 tests performed 6 weeks apart. Coefficients of variation for Kitt and SI were 60 and 47%, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: GTT, ITT, and IST can be performed in cats, using standard protocols. Knowledge of reference values and test variability will enable researchers to better interpret test results for assessment of glucose tolerance, pancreatic beta-cell function, and insulin sensitivity in cats.

Animals↗
PubMed2003

[Reference values for automated reticulocyte analysis].

Reference values for all 7 parameters of the analysis of reticulocytes by using hematological analyzer GEN-S and obtained during blood examination of 115 men and 120 women, aged 20 to 60, are presented in the paper. Reference limits can be used in practical medicine to evaluate the results obtained through an automated analysis of reticulocytes.

Adult↗
PubMed2005

Using physiologically-based pharmacokinetic modeling to address nonlinear kinetics and changes in rodent physiology and metabolism due to aging and adaptation in deriving reference values for propylene glycol methyl ether and propylene glycol methyl ether acetate.

Reference values, including an oral reference dose (RfD) and an inhalation reference concentration (RfC), were derived for propylene glycol methyl ether (PGME), and an oral RfD was derived for its acetate (PGMEA). These values were based on transient sedation observed in F344 rats and B6C3F1 mice during a two-year inhalation study. The dose-response relationship for sedation was characterized using internal dose measures as predicted by a physiologically-based pharmacokinetic (PBPK) model for PGME and its acetate. PBPK modeling was used to account for changes in rodent physiology and metabolism due to aging and adaptation, based on data collected during Weeks 1, 2, 26, 52, and 78 of a chronic inhalation study. The peak concentration of PGME in richly perfused tissues (i.e., brain) was selected as the most appropriate internal dose measure based on a consideration of the mode of action for sedation and similarities in tissue partitioning between brain and other richly perfused tissues. Internal doses (peak tissue concentrations of PGME) were designated as either no-observed-adverse-effect levels (NOAELs) or lowest-observed-adverse-effect levels (LOAELs) based on the presence or the absence of sedation at each time point, species, and sex in the two-year study. Distributions of the NOAEL and LOAEL values expressed in terms of internal dose were characterized using an arithmetic mean and standard deviation, with the mean internal NOAEL serving as the basis for the reference values, which was then divided by appropriate uncertainty factors. Where data were permitting, chemical-specific adjustment factors were derived to replace default uncertainty factor values of 10. Nonlinear kinetics, which was predicted by the model in all species at PGME concentrations exceeding 100 ppm, complicate interspecies, and low-dose extrapolations. To address this complication, reference values were derived using two approaches that differ with respect to the order in which these extrapolations were performed: (1) default approach of interspecies extrapolation to determine the human equivalent concentration (PBPK modeling) followed by uncertainty factor application, and (2) uncertainty factor application followed by interspecies extrapolation (PBPK modeling). The resulting reference values for these two approaches are substantially different, with values from the latter approach being seven-fold higher than those from the former approach. Such a striking difference between the two approaches reveals an underlying issue that has received little attention in the literature regarding the application of uncertainty factors and interspecies extrapolations to compounds where saturable kinetics occur in the range of the NOAEL. Until such discussions have taken place, reference values based on the former approach are recommended for risk assessments involving human exposures to PGME and PGMEA.

Administration, Inhalation↗
PubMed1997

Comfortable and maximum walking speed of adults aged 20-79 years: reference values and determinants.

OBJECTIVES: to establish reference values for both comfortable and maximum gait speed and to describe the reliability of the gait speed measures and the correlation of selected variables with them. DESIGN: descriptive and cross-sectional. METHODS: subjects were 230 healthy volunteers. Gait was timed over a 7.62 m expanse of floor. Actual and height normalized speed were determined. Lower extremity muscle strength was measured with a hand-held dynamometer. RESULTS: mean comfortable gait speed ranged from 127.2 cm/s for women in their seventies to 146.2 cm/s for men in their forties. Mean maximum gait speed ranged from 174.9 cm/s for women in their seventies to 253.3 cm/s for men in their twenties. Both gait speed measures were reliable (coefficients > or = 0.903) and correlated significantly with age (r > or = -0.210), height (r > or = 0.220) and the strengths of four measured lower extremity muscle actions (r = 0.190-0.500). The muscle action strengths most strongly correlated with gait speed were nondominant hip abduction (comfortable speed) and knee extension (maximum speed). CONCLUSIONS: these normative values should give clinicians a reference against which patient performance can be compared in a variety of settings. Gait speed can be expected to be reduced in individuals of greater age and of lesser height and lower extremity muscle strength.

Adult↗
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↗
PubMed1997

Population-specific reference values for bone age.

Contemporary reference values for assessing skeletal maturity have been obtained for the Japanese population. These were used to compare skeletal maturation with populations from the UK. Belgium, North India and South China. Japanese children were found to attain skeletal maturity, based on measurements of the radius, ulna and short bones of the left hand and wrist, 1 or 2 years earlier than present-day European and Chinese children. A relative lack of data for the North Indian population made comparison impossible.

Age Determination by Skeleton↗
PubMed2003

Establishment of reference values for endocrine tests. III: Primary aldosteronism.

BACKGROUND: In our laboratory well-defined reference values for the screening test and confirmation test used in the diagnosis of primary aldosteronism were lacking. In this study we established the reference-values of the plasma aldosterone concentration (PA), plasma renin activity (PRA) and PA/PRA ratio after a two-hour upright period, and of the urinary aldosterone excretion after oral sodium loading. METHODS: Fifty healthy volunteers, equally distributed according to sex and aged between 20 and 70 years, went through the screening and confirmation test of primary aldosteronism. PA, PRA and the PA/PRA ratios were measured after a two-hour upright period (screening test). Urinary aldosterone excretion was determined in two 24-hour urine samples after an oral suppletion of 6 g NaCl a day for five days (confirmation test). RESULTS: The following reference values were established: PA (after two-hour upright position) <0.03-1.05 nmol/l (mean: 0.47), PA/PRA ratio 0.05-0.47 (mean: 0.15) and urinary aldosterone excretion after sodium loading <3.0-47.0 nmol/24h (mean: 10.5). PRA showed a significant decrease with advancing age: median values in the 3rd to 7th decade are 3.9, 3.5, 2.5, 1.6 and 2.1 ng A1/ml/h respectively (p=0.04). PA was lower in subjects > or = 50 years old. Age did not affect the PA/PRA ratio or the urinary aldosterone excretion. There were no significant differences between the sexes in any of the above-mentioned parameters. CONCLUSION: In this study we established reference values for the screening and confirmation test used in the diagnosis of primary aldosteronism.

Adult↗
PubMed1996

Lung function in healthy never smoking adults: reference values and lower limits of normal of a Swiss population.

BACKGROUND: Reference values and definitions of "normal" are prerequisites for population screening and classification of lung diseases. The aim of this study was to calculate reference values for never smoking Caucasian adults. METHODS: In the SAPALDIA cross sectional study respiratory health was assessed in a random sample of 9651 subjects, aged 18-60 years, from eight areas of Switzerland. Lung function was measured according to ATS criteria including quality control. In 3157 healthy never smoking adults without respiratory symptoms the mean values and fifth percentiles of lung function variables were calculated. For each sex, logarithms of lung function were regressed against age, age squared, and the logarithm of height. Residuals were used to estimate fifth percentiles across the age range using a technique not requiring normality or homoscedasticity of residuals. RESULTS: Most lung function variables were non-linear with age and showed an increase in early adulthood and an accelerated decline thereafter. The reference values for forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) were higher than those of the European Community for Coal and Steel and those from North America. The prediction equations for lower fifth percentile values defined a stable proportion of subjects outside this limit whereas alternative methods for estimating the fifth percentile showed a loss of sensitivity with age. CONCLUSIONS: The reference equations for mean values of spirometric indices and their lower fifth percentiles gave an improved and unbiased lower limit of normal. The higher mean values may in part be due to the strictly selected population, quality control procedures, cohort effects, and altitude, and are not explained by the statistical model used.

Adolescent↗