Calculated Reference Intervals Research Articles

Intervalos de referência para elementos menores e traço em cabelo humano para a população da cidade do Rio de Janeiro <FONT FACE=Symbol>-</FONT> Brasil

Inductively coupled plasma mass spectrometry (ICP-MS) has been used for the determination of twenty minor and trace elements in hair samples from an urban population group (N = 1775), aiming at the establishment of reliable hair reference intervals. Statistical evaluation of the data with respect to age, sex and anatomic region was performed by multivariant analysis and according to recommendations of the International Federation of Clinical Chemistry (IFCC). The results show that mainly age and anatomic region (scalp or pubis) influence significantly the concentration of several elements. Comparison of the here calculated reference intervals with those previously published and used by clinical laboratories for this population showed larger discrepancies and the need for an urgent revision of these data.

Reference ranges for serum concentrations of lutropin (LH), follitropin (FSH), estradiol (E2), prolactin, progesterone, sex hormone-binding globulin (SHBG), dehydroepiandrosterone sulfate (DHEAS), cortisol and ferritin in neonates, children and young adults.

The aim of this study was to establish reference ranges for children (neonates to young adults), for serum lutropin (LH), follitropin (FSH), estradiol (E2), progesterone, prolactin, sex hormone-binding globulin (SHBG), dehydroepiandrosterone sulfate (DHEAS), cortisol and ferritin, using the nonisotopic, automated chemiluminescence immunoassay system, Immulite (DPC). Serum samples from 762 children (369 female; age 1 day to 19 years) were examined. Of these, 381 were classified as pubertal. Due to non-normal distribution, the 2.5th, 50th and 97.5th percentiles (central 95% interval) were calculated for each group. Statistical differences between the reference ranges were analyzed with respect to age, sex and the stage of sexual maturation. The median concentrations of E2, prolactin, progesterone, DHEAS, cortisol and ferritin were higher during the first 2 weeks post-partum than thereafter. The largest difference was seen with prolactin, which showed up to 27-fold higher values during this period. In contrast, before the onset of puberty, hardly any sex difference was observed and all analyte concentrations remained relatively constant, apart from SHBG which increased steadily after the neonatal period. The increase of gonadal activity in females with the onset of sexual maturation included an increase in LH and FSH, which was accompanied by a strong increase in E2, progesterone and prolactin. Cortisol increased to a lesser extent during puberty. In males, the increase in the median concentrations of the hormones was smaller, except for DHEAS. The concentration of ferritin was high in the neonatal period but did not change during sexual maturation. Our findings agree with earlier studies. The calculated reference intervals can be used to assess the development of children, particularly for measurements performed by the Immulite and Immulite 2000 chemiluminescence assay systems.

Calculating reference intervals for laboratory measurements

Calculating reference intervals for laboratory measurements

Calculating reference intervals for laboratory measurements.

Reference intervals are used in laboratory medicine to detect measurements which are extreme, possibly abnormal. Methods of estimating reference intervals and age-specific reference intervals (where the measurement is dependent on a covariate, typically age) are reviewed. The issues of calculating confidence bands, determining appropriate sample sizes and assessing goodness-of-fit are discussed.

Reference intervals for the glomerular filtration rate and cell-proliferation markers: serum cystatin C and serum β2-microglobulin/cystatin C-ratio

Recent studies have indicated that serum and plasma cystatin C are better markers for glomerular filtration rate (GFR) than serum creatinine, ubiquitously used for this purpose. To fully exploit the value of serum and plasma cystatin C as GFR markers, reliable age and sex-correlated reference intervals are required. The present study comprised cystatin C determinations in plasma and sera from 259 individuals from a well-defined area in the southernmost part of Sweden. From demographic lists two men and two women were randomly selected from each one-year birth cohort above 20 years of age. No sex differences were found for plasma and serum cystatin C, whereas an increase in the cystatin C levels with age was noted, corresponding to the known age-related decrease in GFR. The following reference intervals are recommended for practical clinical use: S-Cystatin C (both sexes): 20-50 years, 0.70-1.21 mg 1-1 and 50+ years, 0.84-1.55 mg 1-1. The same samples were also used for determination of β2-microglobulin levels in order to calculate reference intervals for the β2-microglobulin/cystatin C-ratio, which is a more distinct marker for cell proliferation, particularly lymphoproliferation, than is the serum level of β2-microglobulin alone, since the ratio should be virtually uninfluenced by GFR. The β2-microglobulin/cystatin C-ratios were uninfluenced by sex and age and 1.45-2.43 is recommended as the serum reference interval for practical clinical use. Serum creatinine was determined in the same samples and the creatinine level was found to be strongly influenced by sex and weakly by age.

The calculation of reference intervals for oxygen availability parameters from measurements on peripheral venous blood

An approach to the calculation of reference intervals for oxygen availability parameters using measurements on peripheral blood is described. The technique involves generating the haemoglobin oxygen dissociation curve from a single point using the technique of Siggaard-Andersen et al. and making the appropriate calculation from the curve.

Reference Intervals for 24-h Urinary Normetanephrine, Metanephrine, and 3-Methoxy-4-Hydroxymandelic Acid in Hypertensive Patients

The urinary excretion of normetanephrine, metanephrine, and 3-methoxy-4-hydroxymandelic acid was quantified by HPLC in hypertensive patients who were being routinely investigated for the exclusion of pheochromocytoma. The data were used to calculate reference intervals for these analytes. Age- and sex-specific 95% reference intervals for 24-h urinary excretion were as follows (mumol/24 h): normetanephrine in men ages 16-35 years (n = 17) 0.7-3.4, in men older than 35 years (n = 121) 0.8-5.1, in women ages 16-35 years (n = 41) 0.5-2.1, and in women older than 35 years (n = 144) 0.6-3.3 mumol/24 h; metanephrine in men (n = 138) 0.3-2.0, and in women (n = 185) 0.2-1.3; and 3-methoxy-4-hydroxymandelic acid in men (n = 142) 10-54, and in women (n = 184) 9-38. Normetanephrine or metanephrine excretion rates or both exceeded the proposed reference intervals in seven of the eight patients with pheochromocytoma. Determination of 3-methoxy-4-hydroxymandelic acid excretion did not yield any additional diagnostic information.

Clinical chemistry reference intervals for healthy elderly subjects

In 1979, 304 healthy elderly individuals in New Mexico were recruited for a longitudinal study of nutrition and aging. Repeat measurements on a yearly basis of commonly requested clinical chemistry analytes allowed the calculation of reference intervals, between and within-subject variance components, and percentiles for change in concentration between two yearly measurements. The latter was further divided into analytical and biological variance components. The upper 95th percentile for the difference between two yearly measurements, expressed as a percent of the population mean, ranged from 4% for Na+ to approximately 20% for total cholesterol and to greater than 90% for ferritin. Year-to-year differences attributable to the biological component ranged from a low of 2% of the population mean for Na+ to 70% for gamma-glutamyltransferase.

Clinical chemistry reference intervals for healthy elderly subjects

In 1979, 304 healthy elderly individuals in New Mexico were recruited for a longitudinal study of nutrition and aging. Repeat measurements on a yearly basis of commonly requested clinical chemistry analytes allowed the calculation of reference intervals, between and within-subject variance components, and percentiles for change in concentration between two yearly measurements. The latter was further divided into analytical and biological variance components. The upper 95th percentile for the difference between two yearly measurements, expressed as a percent of the population mean, ranged from 4% for Na+ to approximately 20% for total cholesterol and to greater than 90% for ferritin. Year-to-year differences attributable to the biological component ranged from a low of 2% of the population mean for Na+ to 70% for gamma-glutamyltransferase.

Application of transformation algorithm and nonparametric calculation in determining the reference intervals of some urine constituents and characteristics

We have applied a multi-stage computer algorithm for normalization of distributions and calculation of reference intervals of some urine characteristics and constituents. The study analyzed 24-h urines, collected from adult male Saudis from different socioeconomic classes, for volume, pH, osmolality, specific gravity, creatine, creatinine, urea and uric acid. Frequency distributions, for each analyte, were found to be nongaussian as judged by the coefficients of skewness and kurtosis, x 2 and Kolmogorov-Smirnov tests, and from probability plots. Data were transformed to gaussian distributions by multistage log-power transformation. Stepwise, this procedure removed skewness and residual kurtosis. Using the gaussian transformed data the reference intervals were estimated parametrically as the mean ± 2 sd. In addition, the non-parametric percentile technique was applied to estimate these values. The former intervals were found to have narrower 0.90 confidence limits than the latter. When established limits were compared with those reported for Western subjects urine volume and uric acid showed the most marked variation.