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PubMed1999

Reference values and biological variation for tumor marker CA 19-9 in serum for different Lewis and secretor genotypes and evaluation of secretor and Lewis genotyping in a Caucasian population.

The concentration of the tumor marker CA 19-9 is influenced by the patient's secretor status and Lewis genotype. The aim of this study was to establish novel reference intervals for CA 19-9 in serum based on secretor and Lewis genotypes, to investigate the biological variation of CA 19-9, and to evaluate the utility of Lewis and secretor genotyping on a group of individuals with serologically defined Lewis phenotypes. CA 19-9 was measured in serum of 500 healthy individuals. Secretor and Lewis genotypes were determined by sequencing and PCR-cleavage methods. Significant differences were found between subgroups with different Lewis and secretor genotypes. Genotype-based reference intervals for CA 19-9 are presented. The upper reference limit for all individuals was 28.7 kilounits/L; for secretors and nonsecretors, the upper reference limits were 12.4 and 61.2 kilounits/L, respectively. The analytical imprecision (CVA) was 9.8%, the within-subject variability (CVI) was 15.8%, and the between-subject variability (CVG) was 102.2%. Good agreement was found between Lewis and secretor genotyping and conventional blood grouping. Genotype-based reference intervals may be a way to increase the clinical utility of CA 19-9. On the basis of the calculation of a critical difference for sequential values (significant at P </=0.05) of 51.5%, a 40-50% change in marker concentration is suggested as the limit for significant change when the marker is used for follow up. PCR-based genotyping is a reliable method for secretor and Lewis histo-blood grouping.

Adult↗

PubMed2002

Reference values for serum levels of vitamin B12 and folic acid in a population-based sample of adults between 35 and 80 years of age.

OBJECTIVES: To examine folic acid and vitamin B12 status in a group of 1000 persons sampled from the community of Umeå, Sweden, and aged 35, 40, 45, 50, 55, 60, 65, 70, 75 or 80 years. Reference data for folate and age-stratified reference data for vitamin B12 are presented, together with an examination of potential confounders. MEASUREMENTS: All subjects participated in extensive health examinations and interviews, and laboratory blood testing was performed. RESULTS: A series of exclusion criteria were applied, and data from 961 subjects were analysed. Vitamin B12 levels were found to decrease with increasing age, whereas folate levels remained constant across the age span studied. None of the vitamins was found to vary with sex, education, smoking or alcohol consumption, body mass index, prescription-free vitamin supplements, level of haemoglobin, or mean cell volume of erythrocytes. Further, none of these factors was associated with the age-related decrease of vitamin B12 level. CONCLUSIONS: The offered reference ranges should be used only in order to rule out deficiency. For B12 levels, the age of the subject should be considered such that, for elderly people in particular, values above the medians should be considered as indicative of normal vitamin status.

Adult↗

PubMed1979

Factors affecting the concentration of triacylglycerols (triglycerides in plasma: reference values for adults.

We studied factors influencing concentrations of triglycerides in the blood of a presumably healthy population of about 9000 persons. Using multi-dimensional analysis, we show, in addition to various related to sex and age, the relation between triglycerides and uric acid, overweight, arterial blood pressure, use of oral contraceptives (in women), consumption of alcohol and tobacco, and lack of physical exercise. These factors were classified as a function of their discriminative power by the statistical method of segmentation. We thus chose the following factors as criteria for exclusion from a reference population for the values of triglycerides in blood: in men 20 to 39 years old, overweight more than 90%; in men 40 to 59 years old, overweight of more than 115%, consumption of more than half a liter of wine per day or of more than 11 cigarettes, use of medicines, and a blood uric acid exceeding 420 mumol/L; in women 20 to 39 years old, contraceptives and overweight; in women 40 to 59 years old, overweight or more than 130% and the intake of medicines. At the 97.5th percentile of the reference population as compared with a non-selected population, the values were 80% less for men 20 to 39 years old, 95% less for men 40 to 59 years old, and only 26 to 30% less for women 20 to 59 years old.

Adult↗

PubMed1989

Reference values for amino acids in cerebrospinal fluid of children determined using ion-exchange chromatography with fluorimetric detection.

One thousand specimens of CSF were collected from subjects ranging in age from newborn to 18 yr, who were undergoing a diagnostic lumbar puncture. Sixty-two samples were judged retrospectively as being suitable for calculating reference age-related values. The analyses were performed by an amino acid analyser using ion-exchange chromatography with fluorimetric detection giving a tenfold increase in sensitivity, thereby enhancing the diagnostic capabilities. As many as 36 known compounds could be detected, additionally 10 we could not identify. In children older than 3 yr nine of the identified compounds showed age-dependency. We found 22 amino acids to be significantly higher in infants younger than 1 yr, with only gamma-aminobutyric acid being significantly lower in infants. Alpha-aminoadipic acid showed a sex difference, being slightly higher in girls.

Adolescent↗

PubMed1989

Transcranial pulsed Doppler measurements of blood velocity in the middle cerebral artery: reference values at rest and during hyperventilation in healthy volunteers in relation to age and sex.

Transcranial pulsed Doppler analysis of blood velocity in the middle cerebral artery was performed in 120 healthy volunteers (age 20-70 y, 12 male and 12 female subjects per decade), meeting strict selection criteria. The intention was to create normative reference data, both at rest and during hyperventilation, for the assessment of abnormality in patients with cerebral vascular disorders. The measured blood velocity at rest decreased significantly with increasing age. Females up to 50 years of age had significantly higher blood velocity values than males. Blood velocity diminution was induced by means of voluntary hyperventilation, under capnographic control. An age related decline of blood velocity as present at rest was not found during hyperventilation, thus the relative value of hyperventilation induced changes diminished with increasing age. The pCO2 related change in the blood velocity index appeared not to be a constant value, as suggested by previous authors. The blood velocity index was largest in the change from resting condition to 4 kPa pCO2, and smallest in the change 3 kPa pCO2 to 2 kPa pCO2. When examining the blood velocity in the MCA, the age, sex and end-tidal pCO2 pressure have to be taken into account for a correct interpretation of the data obtained.

Adult↗

PubMed1975

Some theory of reference values. I. Stratified (categorized) normal ranges and a method for following an individual's clinical laboratory values.

The conventional population-based normal range has recently been shown to be a generally defective reference criterion for assessing individual laboratory test results. Applying a previously derived formula to published data, we find that the use of age-, sex-specific normal ranges may fail to produce a substantial improvement in sensitivity over nonspecific ranges, even when age-sex differences in mean values are statistically significant. This occurs when the difference in means is not accompanied by a sufficient reduction in the variation among individuals within a given class. Turning therefore to comparison of an individual's current measurement with his own previous value(s), I suggest a simple statistical model that leads to sequential testing of each new observation against an exponentially weighted moving average of previous results. Estimates of biological and analytical components of variance are required. The ability of this method to detect trends in very short series is explored with the aid of computer-simulated laboratory data. A sample of these data is also used to illustrate the application of these estimation and testing procedures by means of a graph.

Adult↗

PubMed2005

Reference values of CD4 T lymphocytes in human immunodeficiency virus-negative adult Nigerians.

A cross-sectional study that involved secondary analysis of data collected from 681 pregnant women and 183 miners (94 men and 89 women; ratio of men to women, 1:0.95) in Jos, Nigeria, was carried out to determine the reference ranges for CD4(+)-cell counts in healthy HIV-negative adult Nigerians. The main results of interest were CD4(+)-cell counts and odds ratios (ORs) of low CD4(+)-cell counts, defined as below 350 cells per microl. CD4(+)-cell counts were similar in men and nonpregnant women, with a mean (standard deviation) of 828 (203) cells per microl, but pregnant women had a lower value of 771 (250) cells per microl. None of the factors assessed was related to the odds of having a low CD4(+)-cell count among men and nonpregnant women, but age, age of marriage, and alcohol usage were significant predictors in pregnant women. Compared to pregnant women less than 20 years old, older women had significantly lower odds of a low CD4(+)-cell count (ORs were 0.06 for women aged 20 to 29 years and 0.22 for those aged 30 to 39 years). When compared with those pregnant women who were married before 20 years of age, those who married at 20 to 29 years and 30 to 39 years had odds ratios of 6.41 and 9.40, respectively. Previous alcohol use was also associated with low CD4(+)-cell counts (OR, 5.15). The 95% confidence interval for CD4(+)-cell counts in healthy adult Nigerians is 547 to 1,327 cells per microl, and this is the first time this has been determined.

Adult↗

PubMed1994

Neonatal cerebral Doppler flow velocity waveforms in the uncomplicated pre-term infant: reference values.

In a longitudinal study of 217 infants delivering at < 37 completed weeks gestation, Doppler flow velocity waveforms were obtained and resistance index (RI) values calculated from the middle (MCA) and anterior (ACA) cerebral arteries during the first 10 days of life. One hundred thirty-seven of these infants were non-acidotic at delivery and during the early neonatal period, and had normal cerebral ultrasound scans throughout the study period. These infants formed the reference group. In three gestational subgroups considered (< or = 32 weeks, 33-34 weeks, > or = 35 weeks) from the reference group, the median RI for both the ACA and MCA was noted to fall significantly during the first 12 h of life (P < 0.01 for all groups). For infants delivering at > or = 33 weeks gestation, both MCA and ACA RI values reached a steady state with no significant change in the median value for the remainder of the study period. For infants delivering at < or = 32 weeks, there was a further significant fall in both the MCA and ACA RI between 12 and 24 h of life (P < 0.05), after which a steady state value was reached. During the first 12 h of life the RI for both vessels was significantly higher in infants delivering at < or = 32 weeks compared to the more mature infants (P < 0.01), but for the remainder of the study period, there were no significant differences in RI values between the gestational subgroups.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗

PubMedDate not supplied

[Reference values for protein C activity in healthy adults in Mexico].

Protein C (pC) is a natural-occurring anticoagulant and its acquired or hereditary deficiency has been associated with thrombosis. For its screening, technics that appraise both its plasmatic concentration and biological activity are used. The quantitative deficiency is important, but some characteristics of pC activity (pCA) suggest an essential role of the functional deficiency. Because reference levels have not been previously described in Mexico, we report here the results of a pCA assessed by a chromogenic assay in 88 adult healthy mexican people between 15 and 69 years of age. The pCA values at the 2.5 and 97.5% percentiles in our population were 75 and 137% in normal plasma. Functional disorders of this protein have been described in the presence of normal pC quantitative levels and, therefore, there are individuals with low pC concentrations and a normal pCA without thrombosis. These data suggest that the pCA could be a more important screening test than the quantitative determination as the first step in the study of a possible deficiency state of protein C.

Adolescent↗

PubMed2000

[Additional aids in detection of prostate carcinomas? PSA-prostatic volume quotient, PSA-doubling time, age-dependent PSA reference values and PSA in urine].

Different concepts to improve the clinical utility of prostatic-specific antigen (PSA) for prostate cancer detection have been developed. PSA density and transition zone PSA density are not useful screening tools due to a high variability of prostate volume measurement. PSA velocity monitors the change in PSA in a 2-year period, therefore it is not suitable for treatment decisions in men with serum PSA levels between 4 and 10 ng/ml. Measurement of urinary PSA is not helpful for prostate cancer detection. Age-specific PSA reference ranges provide greater sensitivity for cancer detection in younger men at the expense of a greater negative biopsy rate. In older men unnecessary biopsies could be spared. However, this might lead to a lower sensitivity in these patients, missing possibly clinically insignificant tumors.

Adult↗

PubMed2005

[Reference values for indoor air: dearomatized hydrocarbon solvents (C(9)-C(14))].

To protect public health the German Joint Working Group on Indoor Guidelines of the Federal Environmental Protection Agency and the States' Departments of Health is issuing indoor air guideline values based on a fixed procedure published in 1996. Regarding dearomatized hydrocarbon solvents/white spirits (DAWS--CAS-No. 64742-47-8, 64742-48-9, 64742-88-7, 64741- 65-7) no human data are available. From animal studies, neurotoxicity, developmental toxicity and reproductive toxicity were identified as critical endpoints. For risk evaluation the Hass et al. (2001) study was used as the pivotal study. Based on effects at 4680 mg DAWS/m(3) for the endpoint developmental toxicity, the lowest adverse effect level for chronic exposure is assessed as 400 mg DAWS/m(3). By applying an interspecies factor of 10, an intraspecies factor of 10 and an additional factor 2 referring to the special physiology of children (higher breath rate compared to adults) a so-called health hazard value of 2 mg DAWS/m(3) indoor air and a so-called health prevention value of 0.2 mg DAWS/m(3) are obtained.

Air Pollutants↗

PubMed1997

Reference values for plasma concentrations of vitamin E and A and carotenoids in a Swiss population from infancy to adulthood, adjusted for seasonal influences.

In a cross-sectional survey, plasma concentrations of alpha- and gamma-tocopherol, alpha- and beta-carotene (cis and trans isomers), lycopene, and retinol were determined by reversed-phase HPLC, and ratios of plasma alpha-tocopherol to cholesterol were calculated in 208 Swiss individuals ages 0.4-38.7 years. The influence of age, sex, and season of sampling was studied. Age was a significant predictor of all plasma concentrations except alpha-carotene. No sex-related differences were observed. Season of sampling affected alpha-tocopherol and retinol (higher in winter) and gamma-tocopherol and cholesterol concentrations (higher in winter and spring than in the other seasons). After correction for seasonal influences, age differences were 0.24 micromol/L per year for alpha-tocopherol, 0.04 micromol/L per year for retinol, and 0.04 micromol/L per year for cholesterol concentrations; ratios of plasma alpha-tocopherol to cholesterol were not affected by age. We constructed age-specific reference intervals from the regression line and a multiple of the standard deviation. Separate regression equations are presented for seasons with low and high values.

Adolescent↗

PubMed2004

Reference values for amplitude-integrated electroencephalographic activity in preterm infants younger than 30 weeks' gestational age.

OBJECTIVE: To prospectively investigate the development of amplitude-integrated electroencephalographic (aEEG) activity during the first 2 weeks of life in neurologically normal and clinically stable preterm infants <30 weeks' gestational age (GA). PATIENTS AND METHODS: Infants with a GA of <30 weeks admitted to the neonatal intensive care unit of the Vienna University Children's Hospital (Vienna, Austria) were studied prospectively by using aEEG and cranial ultrasound. Clinically stable infants without clinical or sonographic evidence of neurologic abnormalities were eligible for inclusion in the reference group. The distribution of 3 background aEEG activity patterns (discontinuous low-voltage, discontinuous high-voltage, and continuous), presence of sleep-wake cycles, and number of bursts per hour in the reference group were determined by visual analysis. RESULTS: Seventy-five infants (median GA: 27 weeks; range: 23-29 weeks) were eligible for inclusion in the reference group and had aEEG recordings during the first 2 weeks of life available. Analysis of aEEG background activity showed that with higher GA the relative amount of continuous activity increased while discontinuous patterns decreased. The number of bursts per hour decreased with increasing GA. Cyclical changes in aEEG background activity resembling early sleep-wake cycles were observed in all infants. CONCLUSIONS: Normal values for aEEG background activity were determined in preterm infants <30 weeks' GA. Clinically stable and neurologically normal preterm infants exhibit at least 2 different patterns of aEEG activity. There is a correlation between the GA and the relative duration of continuous aEEG activity.

Circadian Rhythm↗

PubMed1989

Modelling of reference values for size at birth.

Data from the Swedish Medical Birth Registration, 1977-1981 were used to apply methods of constructing reference standards for size at birth. Using clinical information a 'healthy' sub-population was extracted. The conditional distributions of birthweight (BW) and birthlength (BL) for each week of Gestational age, and the conditional distribution of birthweight given birthlength were modelled using truncated Normal distributions, after making use of Box-Cox power transformations. Spline functions were then used in conjunction with a multiplicative method to obtain appropriate percentage point curves. Examples of this analysis are given.

Birth Weight↗

PubMed2003

Height, weight, body mass index and pubertal development reference values for children of Turkish origin in the Netherlands.

UNLABELLED: The aim of this study was to provide growth and sexual maturation reference data for Turkish children living in The Netherlands. We also compared these references with the reference data of children of Dutch origin and with Turkish reference data collected in Turkey and elsewhere in Europe. Cross-sectional growth and demographic data were collected from 2,904 children of Turkish origin and 14,500 children of Dutch origin living in the Netherlands in the age range 0-20 years. Growth references for length, height, weight for height, body mass index (BMI) and head circumference were constructed with the LMS method. Reference curves for sexual maturation and menarche were estimated by a generalised additive model. Predictive variables for height and BMI were assessed by univariate and multivariate regression analyses. Young Turkish adults were 10 cm shorter than their Dutch contemporaries. Mean height was 174.0 cm for males and 160.7 cm for females. Height differences in comparison with Dutch children started at 3 years. Height SDS was predominantly associated with target height. The height of Turkish children living in the Netherlands was similar to Turkish children in Germany and to children from high socio-economic classes in Istanbul. Compared to Dutch children, maturation stages started 0.5-0.7 years later for both sexes. In girls, median age at menarche was 12.8 years, 5 months earlier than in Dutch girls. BMI of Turkish children was higher than that of Dutch children at all ages. BMI SDS was associated with birth weight and the duration of stay of the mother in the Netherlands. CONCLUSION: Turkish children are considerably shorter and more overweight than Dutch children. Separate growth charts for Turkish children in The Netherlands are useful for growth monitoring.

Adolescent↗

PubMed1979

Percentiles as reference values for laboratory data.

It has been suggested that laboratory results be reported, not only in conventional units, but also in terms of equivalent percentiles from a reference population. This would afford the clinician an easily interpretable measure of how unusual such a result would be in the reference population. This paper describes a modified method for estimation of reference percentiles. This method does not require any assumption about the distribution of the reference population, but it has a smaller variability than that from earlier methods based on interpolation. This method is now being used to furnish percentile values for spirometric data in the authors' laboratory.

Clinical Laboratory Techniques↗

PubMed2002

Blood flow velocity waveforms of the fetal middle cerebral artery in a normal population: reference values from 18 weeks to 42 weeks of gestation.

The aim of this prospective cross-sectional study was to establish new Doppler reference curves for peak blood flow velocities (Vmax, Vmean, Vmin) and impedance indices (PI, RI) of the middle cerebral artery at 18-42 weeks of gestation by an automatic wave form analysis integrated into the ultrasound device. In 962 low-risk pregnancies, blood flow velocities were derived from the middle cerebral artery with pulsed color Doppler ultrasonography. Reference curves were constructed for the individual parameters based on a growth function from a four-parameter class of monotonic continuous functions according to the smallest square principle for maximum blood flow velocities, as well as on a polynomial function for resistance indices. Further assessed was intra-observer reliability. The results obtained for maximum blood flow velocities demonstrate a continuous increase (Vmax = 26.8 cm/s to 59.1 cm/s, Vmean = 11.2 cm/s to 29.7 cm/s and Vmin = 4.9 to 15.8 cm/s) over the period from 18 to 42 weeks of gestation. In contrast, reference curves for the pulsatility and the resistance index are characterized by a parabolic pattern (18 weeks: 1.5; 28 weeks: 1.9; 42 weeks: 1.1 and 18 weeks: 0.68; 28 weeks 0.8; 42 weeks: 0.61). Intraobserver reliability for PI, RI, Vmax, Vmean, and Vmax were 87%, 83%, 80%, 83% and 93%, respectively. At constant measurement conditions, the reference ranges for blood flow velocities and impedance indices in the middle cerebral artery established by this study were found to be a useful non-invasive tool in risk assessment for fetal anemia, as well as in the Doppler ultrasound observation of the course in fetuses with intrauterine growth restriction.

Adult↗

PubMed2004

Radiation exposure to patients undergoing percutaneous coronary interventions: are current reference values too high?

PURPOSE: To determine predictors of patient radiation exposure due to percutaneous coronary interventions (PCI) and to compare our results with the "preliminary reference levels", recently proposed by the European DIMOND research cardiology group: i. e., 75 Gy.cm(2) for dose area kerma product (DAP), 17 min for fluoroscopy time (T(F)), and 1,300 for cinegraphic frames (F). MATERIAL AND METHODS: For 642 PCI-exclusive of the fraction for diagnostic catheterization to avoid statistical confounder effects-we measured total DAP, cinegraphic (DAP(C)) and fluoroscopic (DAP(F)) fractions, the number of cinegraphic frames and runs, and T(F). DAP(C)/F and DAP(F)/s were calculated to indicate the quality of focusing to the region of interest. RESULTS: The mean total patient DAP for elective one-, two-, and three-vessel PCI amounted to 6.7, 11.6, and 19.4 Gy.cm(2), for PCI of focal in-stent restenoses to 4.2 Gy.cm(2), and for excimer laser angioplasty of diffuse in-stent restenoses to 19.4 Gy.cm(2), respectively. Recanalization of chronic occlusions and PCI in acute myocardial infarction occasioned mean levels of 16.0 and 17.3 Gy.cm(2). Implantation of one and > or = two stents during one-vessel PCI significantly increased total mean DAP from a baseline level of 5.7 up to 7.1 and to 13.8 Gy.cm(2). DAP significantly varied according to the various PCI target regions and amounted to 4.0, 4.5, and 5.5 Gy.cm(2) for intermedius, diagonal, and left anterior descending arteries, to 4.9, 5.0, and 7.0 Gy.cm(2) for obtuse marginal, left posterolateral, and circumflex arteries, to 8.3, 9.1, and 9.5 Gy.cm(2) for proximal/mid right coronary segments, posterior descending, and right posterolateral arteries, and to 11.6 Gy.cm(2) for saphenous vein grafts, respectively. CONCLUSION: This study, carried through by consistent use of radiation-reducing techniques, enables a reliable scoring of patient radiation exposure according to complexity and target vessel of the intended PCI. Our 95th percentiles for elective PCI, for recanalizations of chronic occlusions, and for emergency PCI advise reference levels of 22, 32, and 42 Gy.cm(2) for DAP, of 16, 25, and 24 min for T(F), and of 400, 600, and 700 cinegraphic frames, respectively.

Angioplasty, Balloon, Coronary↗