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PubMed1999

Establishment of reference values for endocrine tests. II: Hyperprolactinemia.

BACKGROUND: In patients with hyperprolactinemia, the thyrotropin-releasing hormone (TRH) stimulation test is widely applied to distinguish prolactinoma from other causes of hyperprolactinemia. In the present study, we established reference values for the plasma concentration of prolactin (PRL) and its response to TRH. METHODS: Basal PRL and the PRL response to 400 micrograms TRH i.v. was determined in 50 subjects recruited from the general population, equally distributed according to sex and age between 20 and 69 years. PRL was determined by a fluoroimmunometric assay. Reference values are given as the observed range. RESULTS: Plasma concentrations of PRL were 4.0-25 micrograms/l (median: 10.0 micrograms/l) in women and 0.5-19.0 micrograms/l (median: 8.5 micrograms/l) in men (p = 0.11). The peak PRL concentration after stimulation with TRH was slightly higher in women (median: 51 micrograms/l) than in men (median: 41 micrograms/l; p = 0.04) and was reached at t = 20 min in all subjects. The relative increase in plasma PRL (median: 440%) did not show a statistically significant effect of age or sex. In 12 subjects (24%), the relative increase in plasma PRL was lower than 250%, which has traditionally been considered the minimum cutoff for a normal response. There were no effects of smoking and alcohol, but regular ingestion of liquorice was associated with lower basal (p = 0.03) and lower stimulated (p = 0.05) plasma concentrations of PRL. CONCLUSIONS: The present study provides reference values for basal and TRH-stimulated plasma concentrations of PRL.

Adult↗

PubMed1998

Reference values for selected hematologic and biochemical variables in Holstein bulls of various ages.

OBJECTIVE: To determine reference ranges for hematologic and serum biochemical variables of bulls residing at an artificial insemination center. ANIMALS: 225 healthy Holstein bulls categorized by age into yearling, intermediate age, and adult groups. PROCEDURE: Hematologic and serum biochemical analyses were performed on 1 blood and 1 serum sample from each bull. RESULTS: Significant differences associated with age were identified for 25 of 33 variables. Serum creatinine concentration for clinically normal adult bulls (2.44+/-0.33 mg/dl) was higher than previously reported reference values for adult cattle. There was a reversal of the segmented neutrophil-to-lymphocyte ratio between yearling (0.85:1) and adult (2.6:1) bulls. This was associated with a significant and marked decrease in absolute numbers of lymphocytes per microliter between yearling (5,801+/-1,683) and adult (1,307+/-509) bulls. CLINICAL RELEVANCE: Reference values for selected clinicopathologic variables were generated from the data.

Aging↗

PubMed1985

[Factors influencing the diagnosis of lung function and our current reference values--results of the Pathophysiology of Respiration Society].

Reference values for lung function testing were determined of the spirometric volume and ventilation parameters VC, FEV1, RV (n = 3,750), bodyplethysmographic airway resistance and residual volume blood gases in rest (n = 5,779) and exercise (n = 117) considering the main influencing factors age, height, sex. The results were compared with international standards. Eleven laboratories of our country were engaged in examinations. The methods, the measuring conditions, the reference equations, and the valuation are described.

Adult↗

PubMedDate not supplied

Reference values and standards for paired organs.

When estimating reference values for measurements on paired organs, the standard deviation for a single measurement can be obtained to a good approximation simply by ignoring the pairing. In practice, however, there are advantages in the use of conventional standards for pair means and differences.

Anatomy↗

PubMed1996

Transfer factor (diffusing capacity) standardized for alveolar volume: validation, reference values and applications of a new linear model to replace KCO (TL/VA)

Transfer factor (TL) varies with alveolar volume (VA), but not in the manner implied by the carbon monoxide transfer coefficient (KCO (TL/VA)). This paper considers two other simple models (one linear and one exponential) which might standardize TL for VA, and asks the questions: 1) Is either model valid? 2) What are appropriate reference values? and 3) Will the model be useful? The relationship of TL to VA within subjects at different depths of inspiration, and between subjects having lungs of different sizes, were measured and compared. The subjects were asymptomatic, nonsmoking, Caucasian adults, including 31 males assessed in the laboratory and 503 male and female participants in population studies. The linear partial regression coefficients of TL on VA (L corrected for body temperature, atmospheric pressure and water saturation (BTPS)) standardized for height (H) in metres, were similar within- and between-subjects; the coefficients applied over a wide range of values for VA. This was not the case for the exponential model. The resulting reference equations in SI units for males and females were: TL = 11.52 H + 2.72 VA.H-2 - 0.051 Age -12.35. RSD 1.17; and TL = 4.87 H + 2.29 VA.H-2 - 0.019 Age -3.03. RSD 0.92, respectively. The residual standard deviations (RSD) about the new relationships were less than in other series. The new linear model could account for much of the variation between different published reference values for TL; it could be useful clinically, in circumstances when VA deviates from the norm. The model does not explain differences in TL associated with gender. Inclusion of VA.H-2 as a covariate in the reference equation for transfer factor, in addition to age and height, improves the accuracy of prediction of normal transfer factor compared with current reference values; its use suggests that some of the differences between published values is due to the volume term. The equations can be used clinically, and eliminate the need for carbon monoxide transfer coefficient.

Adult↗

PubMed1988

Umbilical artery velocity waveforms: normal reference values for A/B ratio and Pourcelot ratio.

Normal reference values for the umbilical artery Pourcelot ratio and A/B ratio are reported. Thirty-five normal patients were studied serially from 20 weeks to term. The A/B ratio centiles were corrected for non-normality of the underlying distribution by transforming from the Pourcelot ratio values. The correction needed was small during the last trimester, but larger for second trimester data. Of the 35 patients 24 were nulliparous and there was a slight tendency for the waveform indices to be higher in the nulliparae, but the numbers in this study were too small to be conclusive about the effect of parity.

Blood Flow Velocity↗

PubMed2005

[South American camelids in Switzerland. II. Reference values for blood parameters].

In order to establish reference values for blood parameters of South American camelids in Switzerland, 273 blood samples were collected from 141 llamas and 132 alpacas. These animals were classified in three categories (young animals < six months, adult females and males). Forty-one parameters were measured (red blood cell count, white blood cell count, electrolytes, metabolites and enzymes). Significant differences between llamas and alpacas were evident for 26 parameters. This study also showed that differences between young animals, females and males must be taken into consideration. A comparison of blood values with the results of fecal analysis for parasite eggs showed that an infestation with Dicrocoelium dendriticum was associated with elevated activity of two liver enzymes (GLDH and gamma-GT) in the serum. In contrast, no differences were found in the results of blood analyses between animals shedding eggs of gastrointestinal strongyles or not.

Age Factors↗

PubMed1978

On establishing reference values.

In order to establish a range of reference values for any characteristic one can use Gaussian or nonparametric techniques, whichever are most appropriate. One has the choice of calculating tolerance intervals or percentile intervals. A tolerance interval is said to contain, say 95% of the population with probability, say 0.90. A percentile interval simply simply calculates the values between which 95% of the observations fall. If the data can be said to have a Gaussian distribution, the same precision can be obtained with smaller sample sizes than using the nonparametric techniques. In some cases, data which are not Gaussian can be transformed into a Gaussian form and hence make use of the more efficient Gaussian techniques. In both cases, the data should be checked for outliers or rogue observations and these should be eliminated if the testing procedure fails to imply that they are an integral part of the data.

Reference Values↗

PubMed1994

Determination of the urinary metabolites of styrene: estimation of the method evaluation function and evaluation of reference values in Danish subjects.

A European study on styrene exposure was initiated in 1989 to evaluate the health effects of environmental and occupational exposure. A part of this study included the development of an analytical method for use in a biological monitoring program. The urinary metabolites of styrene, mandelic acid (MA) and phenylglyoxylic acid (PGA) were quantitated by a direct and convenient high-performance liquid chromatography method. Urine samples were diluted with eluent and analysed by HPLC with a C8 reversed-phase column and a buffer to acetonitrile (9:1) eluent with a counterion added. The detector used was a variable UV detector and the wavelength was lambda = 210 nm. The method was statistically evaluated by a method evaluation demonstrating no systematic error. The uncertainty was 23.8 mumol/l and 11.5 mumol/l for MA and PGA, respectively. The limit of detection (LOD) of MA is 71.4 mumol/l and the LOD of PGA is 34.5 mumol/l, sufficiently low for the measurement of styrene exposure at a low exposure level. The present study indicates that reference values for MA and PGA are low. The fraction of reference values below LOD was 0.80 for MA and 0.66 for PGA; consequently, the reference values were described by a non-parametric one-sided tolerance interval. The 95% one-sided upper tolerance limits calculated for MA and PGA were 31.0 mumol/mmol creatinine and 20.1 mumol/mmol creatinine, respectively, with the coverage 0.95 +/- 0.045 for both metabolites. The method has been used for biological monitoring in several studies of environmentally and occupationally exposed subjects in concentrations up to 200 mumol/mmol creatinine for MA and 150 mumol/mmol creatinine for PGA.

Air Pollutants, Occupational↗

PubMed2002

Biological monitoring of N, N-dimethylformamide. Reference value for N-methylcarbamoyl adduct at the N-terminal valine of globin as a biomarker of chronic occupational exposure.

OBJECTIVES: The recently identified metabolic product of the industrial solvent N, N-dimethylformamide (DMF), the N-methylcarbamoyl adduct at the N-terminal valine of globin, can be determined after chemical conversion to 3-methyl-5-isopropylhydantoin (MVH). Due to prolonged persistence of the adduct in human erythrocytes (lifetime: 4 months), MVH is a suitable biomarker of integrated exposure to DMF over a period of several months. Here we propose a reference value for MVH, used for biological monitoring of chronic occupational exposure to DMF. METHODS: The reference value for MVH was set equal to its steady-state level in a simulated repeated inhalation exposure to DMF (8 h/day, 5 days/week, >or=20 weeks) at a concentration corresponding to the occupational exposure limits MAK and TLV. The initial data on the toxicokinetic behavior of MVH were obtained after single percutaneous and inhalation exposures to DMF in volunteers. MVH was determined by gas chromatography-mass spectrometry according to Mráz et al. RESULTS: The steady-state level of MVH, attained after repeated inhalation exposure to DMF, 30 mg/m(3), 8 h/day, 5 days/week, >or=20 weeks, was assessed to be approximately 135 nmol MVH/g globin. CONCLUSIONS: We recommend the value of 135 nmol MVH/g globin to be used as a new reference value for biomonitoring of integrated exposure to DMF over a long period. The relationship between the MVH level in globin and the intensity of the exposure to DMF should be further tested in the field studies.

Biomarkers↗

PubMed2006

Determination of 5-methyltetrahydrofolate in cerebrospinal fluid of paediatric patients: reference values for a paediatric population.

BACKGROUND: Cerebral folate deficiency (CFD) has been described as a neurological syndrome associated with low 5-methyltetrahydrofolate (5-MTHF) values in cerebrospinal fluid (CSF) with normal folate concentrations in plasma. Our aim was to analyse CSF 5-MTHF concentrations in a paediatric control population and in patients with various neurological disorders. METHODS: We studied plasma and CSF samples from 63 paediatric controls (age range: 2 days to 18 years, average: 3.8 years) and from 165 patients (age range: 1 day to 22 years, average: 5.0 years) with severe epileptic encephalopathies of unknown origin, movement disorders, Rett syndrome and mitochondrial diseases. CSF 5-methyltetrahydrofolate was analysed by reverse phase HPLC with fluorescence detection (excitation: 295 nm and emission: 355 nm). RESULT: A negative correlation between 5-MTHF values and age of controls was observed (r=-0.468; p<0.0001) and reference values were therefore stratified into 3 age groups. Regarding patients, 122 out of 165 showed normal CSF 5-MTHF values while 43 showed decreased values ranging from profound to mild deficiencies. Increased CSF total protein values were associated with the presence of low 5-MTHF concentrations (chi(2)=7.796; p=0.005). CONCLUSIONS: The application of this method has been useful for the establishment of reference values and for diagnosis of CFD in paediatric patients. Furthermore, increased CSF total protein concentrations should be considered as a marker of a possible CFD.

Adolescent↗

PubMed1996

[Reference values in the diagnosis of anemia in the elderly].

OBJECTIVES: To analyze the usefulness of some reference values for erythropoiesis in the elderly. Methods. A total of 226 individuals older than 65 years (139 females and 87 males) were studied with measurements of hemoglobin (Hb), corpuscular indexes, red blood cell distribution index, serum iron level, ferritin and creatinine. Plasma erythropoietin (EPO) was determined in 72 cases. Values were grouped according to age, younger (126) and older than 76 years (100), and sex. RESULTS: Hb was lower in males older than 76 years than in individuals younger than 76 years but this differences was not observed among women. Serum iron level was low in 13.3% of individuals. Creatinine was higher among males than among women and higher among males younger than 76 years than in males older than 76 years. EPO was higher among the elderly patients than in young adults (p < 0.001), keeping no relationship with age. CONCLUSIONS: With the exception of EPO, the usual reference values for erythropoiesis in the adults can be used for the elderly patients. Despite differences in EPO compared with adults, the quantitation of this finding is useless for the diagnosis of anemia in the elderly.

Aged↗

PubMed2001

Reference values for trace and ultratrace elements in human serum determined by double-focusing ICP-MS.

Reference values for trace and ultratrace elements concentrations in healthy human serum, measured by double-focusing inductively coupled plasma-mass spectrometry (ICP-MS), are presented. Blood donors from Asturias (Spain) were selected as the reference population (n=59). Blood samples were collected, after donation, taking the necessary precautions to avoid contamination. All subjects analyzed had normal renal function and nutritional status, as shown from their creatinine and albumin levels. A total number of 14 elements (Al, Ca, Cr, Mn, Fe, Co, Cu, Zn, Rb, Sr, Mo, Cd, Pb, and U) were monitored almost simultaneously. Serum samples were diluted 1+4 with ultrapure water and matrix interferences were corrected using Sc, Ga, Y, and Tl as internal standards. Fe, Cu, and Zn were also determined by isotope dilution analysis (IDA). Reference trace element concentrations intervals observed containing 95% of the reference distribution after excluding outliers are presented. Fourteen serum samples from hemodialysis patients were also analyzed for comparison. High levels of Al, Cr, Sr, Mo, Mn, Pb, U, Co, and Cu and low levels of Fe, Zn, and Rb were found in the serum samples from hemodialysis patients compared to the corresponding reference values observed in this work.

Adult↗

PubMed1990

Blood ammonia concentration in mice: normal reference values and changes during growth.

To establish normal reference values of blood ammonia concentration in mice, possible factors which may affect blood ammonia determination such as age, sex, strain and sampling site of blood, were investigated by the microdiffusion method. The ammonia concentration in blood collected from the tail (mixture of venous and arterial blood) and left ventricle was significantly higher than that in venous blood collected from the orbital sinus and right auricle. Neither strain nor sex differences were observed. Blood ammonia concentration in newborn pups was 92 +/- 19 micrograms/dl immediately after birth and increased to 184 +/- 22 micrograms/dl 24 hours after birth. This increased level was maintained for a week. By 15 days, it decreased to the level at birth. Thereafter, no significant variation with age was observed. Blood ammonia concentration in mice after weaning, irrespective of age, sex and strain, varied from 38 to 123 micrograms/dl, with a mean +/- SD of 79 +/- 18 micrograms/dl.

Ammonia↗

PubMedDate not supplied

Reference values for Doppler indexes of left ventricular diastolic filling in the elderly.

Congestive heart failure increases in prevalence with age. A large number of elderly subjects with heart failure have either normal or slightly reduced left ventricular (LV) systolic function; their symptoms are due to diastolic LV dysfunction. Reference values for Doppler indexes of LV diastolic filling in a large sample of the very elderly (> 70) have not been reported previously. The objective of this study was to generate reference values for Doppler indexes of LV filling in a population of apparently healthy elderly men and women. A total of 1201 surviving original subjects of the Framingham Heart Study were evaluated by Doppler echocardiography. A subset of 114 rigorously selected healthy subjects (26 men and 88 women) aged 70 to 87 years (mean 76) constituted the study group. Measurements of seven commonly used Doppler indexes were obtained. Mean and 2.5, 5, 10, 25, 50, 75, 90, 95, and 97.5 percentile values for Doppler diastolic indexes were generated. Stepwise regression analyses were performed to determine the relation of diastolic LV filling to age group (70 to 74 years, 75 to 79 years, and 80 years and over), sex, and other clinical variables. Reference values for the various Doppler parameters were generated on the basis of this healthy elderly cohort. There was evidence for a slight progressive decline in indexes of LV inflow with age. In 87% of this elderly population the ratio of peak early to late velocities of LV diastolic inflow was less than 1.0.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed2000

Reference values for selected trace elements in serum of term newborns from the urban area of Rome.

Reference values for Al, Cd, Co, Cu, Li, Mn, Mo, Ni, Rb, Se and Zn, and indicative intervals for Sb are proposed in serum from cord blood of 143 term newborns of the urban area of Rome. On the basis of the eligibility criteria adopted, only babies with gestational age > 37 weeks and body weight at the delivery > 2500 g, i.e., "normal" term infants, were included in this study. With the exception of Cd, Li, Ni and Sb, experimental data for each of the other analytes were found to approach a normal distribution. The estimated references values (in ng/ml) were the following: Al, 1. 12-6.79; Cd, 0.10-0.52; Co, 0.20-0.43; Cu, 140-691; Li, 0.31-2.23; Mn, 0.79-3.26; Mo, 0.36-1.56; Ni, 0.20-3.15; Rb, 196-1302; Sb, 0. 10-1.48 (indicative range); Se, 20.2-69.7; and Zn, 318-1405. For several elements, the information available in the relevant literature does not allow adequate comparisons to be performed. This was actually possible only for Cu, Se and Zn. The correlations between the weights at birth (BW), gestational ages (GA) and elemental concentrations were elucidated. As expected, significant positive correlations were found for Cu and Se with GA and BW, respectively. Strong mutual associations were observed for several other elements, but their interpretation is still debatable.

Birth Weight↗

PubMed2006

Static and dynamic standing balance: test-retest reliability and reference values in 9 to 10 year old children.

INTRODUCTION: Based on the literature, reliability reports and normative data for bilateral stance assessments in elementary schoolchildren are limited. The present study was designed to report test-retest reliability and reference values for postural stability in 9 to 10 years old schoolchildren using the Balance Master system. MATERIALS AND METHODS: Twenty children participated in the reproducibility study (mean age 10.1+/-0.7) including test and retest measurement with a one-week interval. The modified clinical test of sensory interaction on balance (mCTSIB) quantified children's static standing balance. The test for the limits of stability (LOS) measured dynamic standing balance. The study sample to determine reference values consisted of 99 children (mean age 9.8+/0.5). RESULTS: The ICCs for inter-item reliability of the four sensory conditions of the mCTSIB showed fair to excellent reliability (ICCs between 0.62 and 0.80). The reproducibility between test and retest was non-significant for the condition 'firm surface with eyes closed' (ICC of 0.37), fair to good for the three other sensory conditions (ICCs between 0.59 and 0.68), and excellent for the composite sway velocity (ICC of 0.77). For all LOS parameters, the significant ICCs showed fair to good reproducibility (ICCs between 0.44 and 0.62), with the exception of the non-significant ICC for the composite reaction time. The ICCs for the separate LOS parameters showed fair to good and excellent reliability for nine parameters (ICCs between 0.46 and 0.81), while 11 separate LOS scores did not demonstrate significant ICCs. DISCUSSION: Analysing reference values, girls performed better on all the composite balance parameters compared to boys, with the exception of reaction time and movement velocity. No differences were found on standing balance scores between 9 and 10 year olds. CONCLUSION: In conclusion, the Balance Master showed fair to good reliability for most postural parameters in 9 to 10 year olds. The current data on postural control in children aged 9 to 10 years are relevant for research in other domains within the clinical field, like obesitas and developmental coordination disorder or in relation to back pain prevalence at early age.

Child↗

PubMed2006

M-mode and Doppler echocardiographic reference values for male New Zealand white rabbits.

OBJECTIVE: To determine M-mode and Doppler echocardiographic reference values in healthy New Zealand white rabbits. ANIMALS: 52 healthy male rabbits. PROCEDURES: The rabbits were anesthetized and M-mode measurements of the left ventricle, left atrium, and aorta and Doppler measurements of pulmonary and aortic outflow and mitral inflow were recorded. RESULTS: Mean +/- SD heart rate during echocardiographic examination was 155 +/- 29 beats/min. Mean +/- SD measurements in diastole and systole for the interventricular septum thickness, left ventricular internal diameter, and left ventricular free wall thickness were 2.03 +/- 0.37 mm and 3.05 +/- 0.45 mm; 14.37 +/- 1.49 mm and 10.25 +/- 1.22 mm; and 2.16 +/- 0.25 and 3.48 +/- 0.55 mm, respectively. Mean +/- SD left atrial-to-aortic diameter ratio was 1.17 +/- 0.14, and mean +/- SD mitral valve E-point-to-septal separation interval was 1.71 +/- 0.29 mm. Mean +/- SD for fractional shortening and ejection fraction were 30.13 +/- 2.98% and 61.29 +/- 4.66%, respectively. Mean +/- SD maximal aortic and pulmonary artery outflow velocities were 0.85 +/- 0.11 m/s and 0.59 +/- 0.10 m/s, respectively, and the peak E-to-peak A wave velocity ratio of the mitral valve was 2.19 +/- 0.46. CONCLUSIONS AND CLINICAL RELEVANCE: Results provide echocardiographic reference values for young adult male New Zealand white rabbits anesthetized with ketamine and medetomidine. Values obtained from unanesthetized rabbits, rabbits sedated with other agents, or rabbits of different size may differ from those reported here.

Animals↗